7th Science Workbook.pdf

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VII CBSE

Physics – Motion

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Question 1. When we are in a train, the trees seem to move backwards. But when we are standing on ground, they appear still. How is it possible for the trees to be moving sometimes while stationary at other times?

a. What is motion? Motion is one of the most important topics in physics. We see a lot of objects around us which are moving. For instance, we see cars running on roads, birds flying etc. While other objects like buildings appear to be at rest. But the same buildings seem to be in motion if viewed from a moving car. Don't forget that even if you appear to be standing still, the Earth is moving around the Sun, and the Sun is moving around our galaxy. The galaxy itself is speeding around at great speeds. When we think of motion, the first thing that comes to our mind is that something is changing its position with time. Of these moving bodies, some appear to move faster while others slower. But there is much more to this motion.

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VII CBSE Physics – Motion Question 2. Suppose a person A is standing on the ground while persons B and C are moving on rollers as shown.

Now fill in the following table based on your understanding of motion. Observer

Person

A

A

Moving / At rest

B C B

A B C

C

A B C

So we see that motion of a body depends on the observer or with respect to what we are observing the motion.

 

Misconception: A body can be at rest or in motion. Clarification: There is nothing as absolute rest or motion. This is all relative.

b. How far? As a moving body changes position with time, there should be some measure of how far the body has moved. And this can be measured by measuring the length of the path which is represented by a number followed by a unit.

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VII CBSE Physics – Motion Question 3. In which of the following cases has the body moved more?

Did You Know? An instrument called odometer measures the distance travelled by vehicles. Around 15 BC, the Roman architect and engineer Vitruvius mounted a large wheel of known circumference in a small frame; when it was pushed along the ground by hand, it automatically dropped a pebble into a container at each revolution, giving a measure of the distance traveled. It was, in effect, the first odometer.

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VII CBSE

Physics – Motion

2. Basics of Standard Units a. Standardization: What and Why? As we learnt, to represent the motion of a body we need a number followed by a unit. This unit should be a standard unit which is accepted universally by all. E.g. First aid whose symbol is universally accepted is shown below.

Figure 1: Example of Standardization

Now we are going to strict to standardization of length only. Earlier different units were used as units of length like length of feet, cupid etc. But these were not standard and could vary from person to person. Even for the same person, its value changes with time. A better unit would be a rod of given length. Question 4. What are the advantages and disadvantages of using a rod of given length as a unit of length?

A still better way would be to define a unit based of speed of light. For example, a meter is defined as the distance travelled by light in has been accepted universally. b. Smaller and Larger Units

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s. This value is not going to change and

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VII CBSE

Physics – Motion

Question 5. Why do we need smaller units of length?

1 meter = _________________ centimeter 1 millimeter = _________________ meter Similarly, we also need some larger units of length to measure greater lengths. For instance, the distance between Bangalore and Delhi is 1,740,000 m while that between Bangalore and Mysore is 147,000 m. If we define 1 kilometer to be 1000 m, we can easily represent these distances as 1740 km and 147 km. 1 meter = _________________ kilometer Question 6. Akash found on the internet that sounds travel 1480 m in one second in water. His friend, Susweta argues that it travels only 1.48 km in a second. Who do you think is right? Justify your answer.

3. Basics of Motion and its Types a. Motion Basics So what are the parameters that can be used to determine whether a body is moving or not? One way is that if the body is moving in a straight line along the line of sight of the observer, it will either seem to approach you (with time its size will increase) or recede away from you (its size will decrease).

Figure 2: Perception of Motion

Yet another way is that you have to rotate your head in order to keep looking at the body.

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VII CBSE

Physics – Motion

Figure 3: Another Perception of Motion

Question 7. How can you say that moon is in motion with respect to you standing on the earth?

b. Different Types of Motion The motion of bodies that we encounter in our daily lives can be of different types- rectilinear, circular, periodic or any random motion. If a body moves in a straight line, its motion is said to be rectilinear and if it moves on a circular path, it is said to be in circular motion. However, if it repeats its motion in equal intervals of time, the motion is said to be periodic.

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VII CBSE Physics – Motion Question 8. Classify each of the following motions into different types with proper justification of your choice.

A swing:

 

A car moving on a straight road:

Blades of a moving fan:

Misconception: A car moving on a circular track is in periodic motion. Clarification: A car moving on a circular track need not necessarily be in periodic motion. It might not pass the same point after equal intervals.

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VII CBSE

Physics – Motion

4. Time and Speed a. Time In order to better analyze the motion of a body, along with knowing how far it has moved, it is also important to know how much time it has taken for it. We understand what time is. However, defining time is not an easy task.

Figure 4: An Hour Glass

Question 9. How do you think an hour glass can be used to measure time?

Did You Know? Galileo discovered that as long as a pendulum stays the same length and keeps swinging, the time it takes to swing back and forth is always the same. This makes a pendulum the ideal timekeeper.

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VII CBSE Physics – Motion b. Speed Suppose a car is moving on a straight road. In some time it covered a distance .

Figure 5: Car moving on a straight road

Then speed is the quantity that takes into account both the factors:  How far the body has moved?  How much time it has taken?

In fact, it gives the average speed of the car as the car can travel different distances in different intervals of time. And such motion is called non-uniform motion. On the other hand, if a body covers equal distances in equal intervals of time, its motion is uniform.

Did You Know? On Saturn, wind speeds can reach as high as 1609 km/h, which is just about as fast as a speeding bullet. The highest wind speed ever recorded on Earth during a hurricane was in 1996, during Tropical Cyclone Cynthia when gusts reached 408 km/h.

Question 10. A bus is in uniform motion and it covers a distance of 10 km in 1 hour. How much distance will it cover in the next 30 minutes?

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VII CBSE

Physics – Motion

5. Motion Visualized In order to represent motion, we need to have a reference. This is known as the origin. The paper is moved at a constant rate towards the right and represents time. On the other hand, position is represented perpendicular to the time.

Figure 6: The Coordinate System

For instance in the above figure, at time t = 2 s, the body is at 3 m. Question 11. What is the importance of having a negative position?

For a body moving at a constant speed, starting at time t = 0 from origin, if it moves 3 m in 2 s, it is represented in the graph as shown below.

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VII CBSE

Physics – Motion

Figure 7: Body Moving at a Constant Speed

Question 12. How would the graph look like if the body had covered 4 m in the same 2 seconds?

So we see that if the body has more speed, the line is inclined at a greater angle; we say that slope of the graph is more.

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VII CBSE

Physics – Motion

Instructions: Solve these problems after watching the videos. 1) 2) 3) 4) 5)

While specifying whether a body is at rest or in motion, why do we need an observer? Suppose you are in a ferry sailing across the Indian Ocean. How will its motion look like to you? What is standardization? What is its importance? The SI unit of length is meter. Then why are smaller and larger units of length required? Which of the following bodies have greater speed? Justify your answer.

6) 7) 8) 9)

How can you say that a body is in motion with respect to an observer? Under what conditions will the speed be equal to average speed of a body? What are the different types of motion? Give examples for each. What do you mean by time period of a simple pendulum? How can a simple pendulum be used to measure time? 10) Differentiate between uniform and non-uniform motion citing proper examples. 11) The motion of a body is shown graphically. What can you conclude about its motion?

12) What do you mean by slope of a graph? What is its importance with respect to position-time graph? 13) Akash takes 20 minutes to go from his house to a friend‘s house on a bicycle. If the bicycle has a speed of 1 m/s, calculate the distance between their houses.

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VII CBSE

Physics – Motion

14) The motion of a body is graphically represented as shown below. What is its speed?

15) A body covers a distance of 10 m in 20 s and then another 10 m in 10 s. Represent its motion graphically assuming the body to be in uniform motion. 16) The SI unit of time is A) Hour C) Second B) Minute D) None of these 17) A simple pendulum takes 2 s to move from A to B. Then its time period is

A) 2 s B) 4 s 18) The path completed for 1 complete oscillation is

C) 6 s

A) A-B-A B) A-B-A-C 19) Motion of moon around the earth is A) Rectilinear B) Circular 20) Why can‘t you use rod as a standard unit of length? A) Its length can change with change in temperature. B) It can corrode with time. C) It can‘t be reproduced accurately.

C) A-B-A-C-A D) None of these

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D) 8 s

C) Periodic D) Both circular as well as periodic D) All of these

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VII CBSE

Physics – Heat

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Question 1. Your friend touches your forehead and says that you have fever. Can you definitely say that he/she is correct?

a. Hot and Cold Bodies Of the various objects that we come across in day-to-day life, some seem to be hot, while others may seem to be cold. Even out of these objects, some seem to be relatively hotter or colder. And we generally use the perception of touch to determine this. Question 2. Can you classify the following bodies as hot or cold? Body A furnace Ice tea Tap water Base of an iron Pencil Molten wax

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Hot/Cold

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VII CBSE Physics – Heat b. Perception of Touch Well, our perception of touch is not a reliable method to determine whether a body is hot or cold. It is somewhat relative; the same body may appear to be hot to one person, while cold to another.

Figure 1: Different Perception of Same Water

2. Visualizing Heat When it comes to visualization of heat, we are not that lucky that directly by seeing a body we can determine whether it‘s hot or cold. However, pythons, rattlesnakes and other members of the family known as the 'pit vipers' have a sixth sense that can sense minute temperature changes which acts as an aid in locating warm-blooded prey such as rodents. Question 3. At the microscopic scale, how will a hot body be different from a cold body?

We see that at the microscopic level, a hot body looks different from a cold body. When these two bodies are brought in contact, the active atoms of the hot body collide with the relatively less active atoms of the cold body. The more energetic atoms lose energy and slow down, while the reverse happens for the less energetic atoms. Eventually the motion of both bodies equalizes and they are equally hot or cold. So we can perceive hotness as the amount of motion at microscopic level.

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VII CBSE

Physics – Heat

Figure 2: A Hot and a Cold Body at Microscopic Level

Till now we have qualitatively defined hotness or coldness. In quantitative terms, temperature is the measure of random energies inside a body. Question 4. When does heat flow between two bodies?

Heat flows from a body at higher temperature to a body at lower temperature. If the two bodies are at the same temperature, no heat flows between them. This is known as thermal equilibrium.

Figure 3: Zeroth Law of Thermodynamics

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VII CBSE

Physics – Heat

Question 5. Suppose you have three bodies A, B and C. When A and B are brought in contact, no heat flows between them. Now when B and C are brought in contact, heat flows from B to C until flow of heat stops. What will happen when A and C are brought in contact?

 

Misconception: Heat flow between two bodies occurs from a body with higher heat content to a body at lower heat content. Clarification: Heat flow between two bodies always occurs from a body at higher temperature to a body at lower temperature, irrespective of their heat content.

3. Measuring Temperature Temperature is a measure of degree of hotness or coldness of a body. Since we can‘t directly visualize temperature, we need something that changes properties with change in temperature. And then only we would be able to measure temperature. For this purpose of measuring temperature, expansion of mercury can be used.  Mercury, being a liquid, can be put in any container.  With an increase in temperature, it expands and with a decrease in temperature, it contracts.  It is a good conductor of heat. A thermometer is a device that is used to measure temperature. One of the most common types of thermometer is the laboratory thermometer. In this type of thermometer, an expansion liquid, usually Mercury or Alcohol, fills a glass bulb attached to a long stem. When heated, the liquid expands up the stem until the bulb reaches thermal equilibrium with the material whose temperature is being measured. The expansion of the liquid is such that the height it reaches in the stem is linear with temperature. A laboratory thermometer (calibrated from -10°C to 110°C) is shown below.

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VII CBSE

Physics – Heat

Figure 4: A Lab Thermometer

Did You Know? The highest temperature ever recorded in the shade was 57.8°C in Libya on September 13 1922.

Question 6. How is a laboratory thermometer calibrated?

Another type of thermometer is the clinical or medical thermometer. It is used for measuring human body temperature. It is calibrated from 35°C to 42°C as the temperature of human body does not go below. Question 7. Why can‘t you use a laboratory thermometer to measure the temperature of your body? How does a clinical thermometer solve this problem?

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VII CBSE

Physics – Heat

Figure 5: A Clinical Thermometer

Question 8. While measuring temperature of boiling water, Susweta found the temperature to be 85°C only. What can be the probable reason for this?

4. Messengers of Heat Ever wondered how heat from the sun reaches the earth. Or why do you feel hot near fire, even though you don‘t directly touch it. Or why a metallic spoon kept in tea feels hot. Well it‘s all because of transfer of heat, although the means by which heat gets transferred is different. Though the term "cold" has plenty of meanings in the everyday world, in physics, it does not. Cold and heat are analogous to darkness and light: again, darkness means something in our daily experience, but in physical terms, darkness is simply the absence of light. If you grasp an ice cube in your hand, your hand gets cold. Our mind perceives this as a transfer of cold from the ice cube, but, in fact, exactly the opposite happens: heat moves from your hand to the snow. And this is what you experience as a sensation of coldness. Basically there are three means by which heat can be transferred from one body to another:  Conduction  Convection  Radiation Solids, particularly metals, whose molecules are packed relatively close to each other, are the best materials for conduction. Molecules of liquid or nonmetallic solids vary in their ability to conduct heat, but gas is a poor conductor, because of the loose attractions between its molecules.

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VII CBSE

Physics – Heat

Figure 6: Heat Transfer by Conduction

 

Misconception: Cold flows from a cold to a hot body. Clarification: It’s always the heat that follows from hotter body to the colder one.

Question 9. How does a conductor of heat differ from an insulator? Give examples for each.

Question 10. How does heat transfer take place by convection? Can heat transfer by convection take place in solids?

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VII CBSE

Physics – Heat

Figure 7: Heat Transfer by Convection

Did You Know? Convection also takes place within the Sun. Vast amounts of hot gases rise up towards the surface of the Sun. As they do so, they become cooler and begin to fall back down towards the center of the Sun. And the process continues.

Sea Breeze

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Land Breeze

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VII CBSE

Physics – Heat

Figure 8: Sea Breeze and Land Breeze

Let us now come to the third means of heat transfer – Radiation. For instance, heat from the sun is not dependent on any fluid medium for its transfer; it comes to the Earth by the means of radiation. This is a form of heat transfer significantly different from the other two, because it involves electromagnetic energy, instead of ordinary thermal energy generated by the action of molecules. Every form of matter emits electromagnetic waves, though their presence may not be readily perceived. Thus, when a metal rod is heated, it experiences conduction, but part of its heat is radiated, manifested by its glow—visible light. Even when the heat in an object is not visible, however, it may be radiating electromagnetic energy, for instance, in the form of infrared light.

Figure 9: Heat Transfer by Radiation

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VII CBSE

Physics – Heat

Question 11. Explain an example where heat is transferred by all the three means.

5. Heat and Fashion The concepts of heat even influence the types of clothes we prefer to wear during winter and summer – Whites and light colored clothes for summer while black and dark colored clothes for winter. Dark-colored objects absorb radiation better than the light-colored objects. That is the reason we feel more comfortable in light-colored clothes in the summer. Did You Know? The skin of a polar bear is black, which helps it to absorb more of the heat from the sun.

Question 12. Why is it so that if you wear two thin sweaters, you will feel warmer as compared to a single thick sweater?

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VII CBSE

Physics – Heat

Instructions Solve these problems after watching the videos. 1) Describe an experiment to conclude that touch is not a reliable perception of heat and temperature. 2) How do you measure temperatures in a laboratory? 3) State the zeroth law of thermodynamics. 4) A lab thermometer, calibrated from -10°C to 110°C, is divided into 12 large divisions and each of the large divisions is further divide into 5 small divisions. What minimum temperature can you measure using this thermometer? 5) Why are steel utensils provided with a copper base? 6) How does heat from sun reach the earth surface? 7) We prefer to wear light colored clothes in summer. What is the reason for this? 8) When standing barefoot in a cool room having both carpet and tile flooring, the tile feels colder than the carpet. What can be the reason for this? 9) If you hold a thermometer by its bulb, will the reading be accurate? Why/Why not? 10) Explain how land breeze and sea breeze are formed. 11) If you place your hands over a heat flame, you feel hot. How does heat reach your hand? 12) How can woolen clothes keep you warm in winters? 13) Why is there a kink provided in the clinical thermometer? 14) With the help of an experiment, show that in convection actual motion of particles takes place. 15) Whether heat will flow between two bodies depends on what factor/factors? 16) In which phase does conduction take place the fastest? A) Solid C) Gas B) Liquid D) Both liquid and gas 17) Which of the following is an insulator? A) Iron C) Wood B) Copper D) Steel 18) 5 litres of water at 20°C is mixed with 1 litre of water at 50°C. The resulting temperature will be A) < 20°C C) Between 20°C and 50°C B) > 50°C D) Can‘t say 19) A body A at 30°C is placed in contact with another body B at 30°C. Heat will flow from A) A to B C) No heat will flow B) B to A D) Can‘t say 20) The range of clinical thermometer is from A) 32°C to 40°C B) 35°C to 47°C C) 32°C to 42°C D) 35°C to 42°C

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VII CBSE

Physics – Electric Current and its Effects

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Electricity is one of the most amazing phenomena that we encounter in our daily lives. In fact, imagining a life without electricity is highly unimaginable! Question1.What is some applications where we use electricity in our daily lives?

Humans have been aware of this force for many centuries. Earlier it was believed that electricity was some form of magic because people did not understand it. Greek philosophers noticed that when a piece of amber was rubbed with cloth, it would attract pieces of straw. They recorded the first references to electrical effects over 2,500 years ago. Today we use electricity to light our homes, power our televisions, washing machines, geysers and many more appliances. If you've ever seen a thunderstorm, with mighty lightning bolts darting down from the sky, you'll have some idea of the power of electricity. A single lightning bolt is enough to light 100 powerful lamps for a whole day! Electricity has played a vital part of our past, continues to affect our present significantly and could play a different role in our future. Let's take a closer look at electricity! Did You Know? The light reaching our eye is converted into electrical signals that the brain can interpret.

2. Symbols of Electric Components

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VII CBSE Physics – Electric Current and its Effects Question2. What do you mean by an electric circuit?

Representing an electric circuit using actual components can be quite clumsy and cumbersome, especially when the circuit involves multiple components. So we represent different components of the circuit using symbols. Component

Battery

Switch Off

Wire

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Symbol

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VII CBSE Physics – Electric Current and its Effects Question 3. Suppose you have 4 cells as shown below. How will you connect them to make a battery with A as negative terminal and B as positive? Also show its electrical symbol with terminals properly marked.

Did You Know? The voltaic pile, invented by Alessandro Volta in 1800, was the first electric battery. Its invention can be traced back to an argument between Volta and Luigi Galvani, Volta's fellow Italian scientist who had gained notoriety for his experiments on frog legs. Galvani discovered how a circuit of two metals and a frog's leg can cause the frog's leg to respond.

Using these electrical symbols, we can represent the circuit quite conveniently. When the circuit is complete, current flows through it. For example, a simple circuit using a cell, switch, bulb and wires is shown below where the bulb glows when current flows through it.

Figure 1: A Closed Circuit

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VII CBSE Physics – Electric Current and its Effects Question4.Draw a circuit diagram for the above situation when the switch is in ―off‖ position.

 

Misconception: The electrons, which flow in the circuit, are provided by cell/battery. Clarification: Batteries and cells do not create these electrons, they merely pump them

Question5. Why do you think we require wires to connect the components? Can‘t electricity flow through air?

Let us now examine an important effect of electric current.

3. Heating Effects of Electric Current a. Electric Bulb We have seen that a bulb glows when current flows through it. It also becomes hot. So how does the bulb emit light and heat? The electric bulb consists of a thin wire, called the filament, which glows when an electric current passes through it. The filament is usually made of tungsten. When current flows through the filament, the electrons collide with the stationary atoms and they start vibrating about their mean positions. This causes heating of the filament and is known as Joule’s heating. As it heats up, the wire emits most of its heat as infrared radiation. Some of this heat energy, however, is actually emitted at slightly higher frequency radiation, which we can see as light.

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VII CBSE

Physics – Electric Current and its Effects

Figure 2: Collision of Electrons with Atoms

Question 6. Why is tungsten used for making filaments in an electric bulb?

Did You Know? Fireflies produce light using chemical energy from their food. This light is even more efficient than that of one light bulb. Other creatures possess this magic too, like the deep-sea squid and glow-worms. An electric eel on the other hand, does not glow, but it can produce strong electric shocks.

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VII CBSE

Physics – Electric Current and its Effects

Question 7. When current flows through the filament of a bulb it gets heated to such a high temperature that it starts glowing. However, the wires used for making electric circuits do not normally become that hot. Why is it so?

Question8.While demonstrating the heating effect of electric current, a student used a cell in the first case and a battery consisting of 3 cells in the second case. In which case will the heat produced be more? Why?

But if a very large current passes through a wire the wire may become so hot that it may even melt and break. The amount of heat produced in a wire depends on its  Material  Length and  Thickness As per our requirements we use wires of different materials, lengths and thicknesses.

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VII CBSE

Physics – Electric Current and its Effects

Question9.Why CFL bulbs are preferred over incandescent bulbs?

b. Electric Fuse Another electrical component that utilizes heating effect of electric current is the electric fuse. It is used as a safety device in household circuits and controls the amount of current in circuits. There is a maximum limit on the current, which can safely flow through a circuit. If the current exceeds this safe limit due to any reason, the fuse breaks the circuit and prevents current from flowing.

Figure 3: An Electric Fuse

Fuse is made using wires made from some special materials having low melting point such that they break when large electric current are passes through them. In case of current exceeding the safe limit, the connecting wires may become overheated and cause fire. If a fuse of proper rating is there in the circuit, it will blow off and break the circuit, hence preventing potential damage. The excessive current can be because of following reasons:  Overloading  Short circuit Question10.How does short circuit differs from overloading?

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VII CBSE Physics – Electric Current and its Effects c. Miniature Circuit Breaker (MCB) MCB is also a safety device, which is now being increasingly used instead of fuse. These basically are switches, which automatically turn off when current in a circuit exceeds the safe limit. They have to be turned on manually such that the circuit gets completed again.

Figure 4: A Miniature Circuit Breaker

Question11.What is the advantages of using an MCB over a fuse?

Having understood the heating effects of electric current, let us now see how electricity and magnetism, which seem to be totally unrelated, are in fact two sides of the same coin! Topics to be covered in the next class:  Magnetic Effects of Electric Current  Electromagnet  Electric Bell

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VII CBSE

Physics – Electric Current and its Effects

4. Magnetic Effects of Electric Current To demonstrate magnetic effects of electric current, you can take a conducting wire (like copper). Now with the help of connecting wires, attach this to the two terminals of a battery. Keep a magnetic needle parallel to the conducting copper wire as shown in figure. When the circuit is complete, the magnetic needle shows some deflection. However, when the current is switched off, the needle comes back to its original position.

Figure 5: Demonstration of Magnetic Effect of Electric Current

Question12.How does the above experiment show that electric current has magnetic effects?

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VII CBSE Physics – Electric Current and its Effects Question 13. What will happen if i) Direction of current is reversed in the above case? ii) Two batteries are used instead of one?

Thus flow of electric current through a conducting wire produces magnetic effects. In the year 1820, a scientist from Denmark named H.C. Oersted observed this effect for the first time. Did You Know? Heat and the Earth’s spin keep the outer core moving. This movement causes electrical currents in the core, which is mostly iron. The electrical currents make the earth behave like a large bar magnet.

5. Electromagnet We all have seen cranes picking up large cars and vehicles. How is it possible? Some might argue that it is some magnet (similar to fridge magnets that you play with but a much stronger one), which can attract the vehicles. But then how is it that the cranes drop the vehicles when and where required. A permanent magnet would not lose its magnetism that easily. You need to hit it hard or heat it so that it loses magnetism and then it won‘t be useful anymore.

Figure 6: A Crane

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VII CBSE Physics – Electric Current and its Effects It turns out that here we utilize magnetic effects of electric current – Electromagnet. An electromagnet is a type of magnet in which the magnetic effect is produced by an electric current, which disappears when the current is turned off. It consists of a large number of closely spaced turns of wire.

Figure 7: An Electromagnet

Question 14. Can an electromagnet be used to separate plastic wastes from a garbage heap? Justify your answer.

When current is being passed through the coils of an electromagnet, it behaves as a bar magnet.

Did You Know? The high-speed maglev trains are developed using electromagnets. These trains float over a guide way using basic principles of magnets; hence replacing the traditional steel wheel and track system.

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VII CBSE Physics – Electric Current and its Effects Question 15. Differentiate between an electromagnet and a permanent magnet. Electromagnet

Permanent Magnet

Question 16. How can the strength of an electromagnet be increased?

 

Misconception: Any material can be used as a core of an electromagnet. Clarification: Not any material can be used as a core of an electromagnet. For example, if hard iron core is used, it won’t lose its magnetism instantaneously when the current is switched off. So, soft iron cores should be used.

Electromagnets find applications in a number of fields:  They can be used to lift very heavy loads. E.g. Electromagnetic cranes  They can be used to separate magnetic material from the junk.  They are used in electromagnets.  Doctors use small electromagnets to remove pieces of magnetic material that have accidentally fallen in the eye.  Many toys also use electromagnets inside them. Now let‘s look into one of the commonly used applications of electromagnets: The electric bell.

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VII CBSE

Physics – Electric Current and its Effects

6. Electric Bell The circuit of an electric bell is shown below:

Figure 8: An Electric Bell

An electric bell consists of a coil of wire wound on an iron piece, which acts as an electromagnet. A striker (which is basically an iron strip with a hammer at one end) is kept close to the electromagnet. There is a contact screw near the iron strip. When the iron strip is in contact with the screw and the switch is in on position current flows through the coil, which then becomes an electromagnet. It then pulls the iron strip. In the process, the striker strikes the gong of the bell and a sound is produced. Question 17. How is it ensured that a repetitive sound is produced as long as the switch is in ―on‖ position?

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VII CBSE

Physics – Electric Current and its Effects Did You Know? There sits, in the Clarendon Laboratory at Oxford University, a bell that has been ringing, nonstop, since 1840. It's powered by a single battery and has rung roughly 10 billion times! However, it is not known with certainty as what the battery is made up of!

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VII CBSE

Physics – Electric Current and its Effects

Instructions Solve these problems after watching the videos. 1) Why do we need symbols of electrical components? Draw the electrical symbols of A) A bulb B) A switch 2) How does an open circuit differ from a closed circuit? In the circuit shown below if the bulb A gets fused, will the bulb B glow? Justify your answer.

3) 4) 5) 6)

If a battery consists of 3 cells, how many terminals will it have? Explain using a diagram. How does an incandescent bulb produce light when electric current passes through it? On what factors does the heat produced in a wire depend? Name two devices utilizing A) Heating effect of electric current B) Magnetic effect of electric current 7) Why is tungsten used for making bulb filament? Why don‘t we use other materials like copper or nichrome? 8) An incandescent lamp wastes a large amount of energy as heat. How can this be minimized? 9) Under what conditions can the current in a circuit exceed the safe limit? 10) What is an MCB? Why is it preferred over a fuse? 11) Explain an experiment demonstrating magnetic effects of electric current. 12) What are the advantages of using an electromagnet over a permanent magnet? 13) Explain using a diagram the construction and working of an electric bell. 14) An electrician while carrying out some repairs in a building replaces the fuse by a piece of wire. Do you think he has done the right thing? Justify your answer. 15) How can the strength of an electromagnet be increased? 16) When do we use a battery instead of a cell? A) When we require more than two terminals. B) When current requirement is less. C) When current requirement is more. D) None of these

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VII CBSE

Physics – Electric Current and its Effects

17) A cell with A as positive terminal and B as negative terminal is represented as

A) C) D) None of these B) 18) A fuse is used to prevent damage in case of A) Overloading C) Short-circuit B) Under loading D) Both A and C 19) A soft iron core is placed inside an electromagnet to A) Retain its magnetic properties even after the current is switched off. B) Increase the strength of electromagnet C) Both of these D) None of these 20) When the switch S is closed,

A) B) C) D)

Both the bulbs glow simultaneously. Bulb A glows first. Bulb B glows first. None of the bulbs glows.

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VII CBSE

Chemistry – Acids, Bases and Salts

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Have you ever wondered why lemon tastes sour whereas tamarind tastes tangy? Each day, we come across numerous things which are different from each other and behave differently. Our curiosity to understand such things led to putting various things in categories to understand them further. On the same line, we categorized food items according to the taste it gave us. Taste the following substance and write the result Substance

Taste

Vinegar Salt Milk You might find the taste as sour, bitter or sweet, but why do they taste differently? In early days, these substances were distinguished as acid and bases according their taste.

2. Acid and Bases Write the definition of acids and bases.

 Acids turn blue litmus paper red  Bases turn red litmus paper blue Question1. If you are provided with a blue litmus paper and asked to dip it in vinegar solution, what will be your observation?

Question2. Give examples of acids which are used in everyday life?

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VII CBSE

Chemistry – Acids, Bases and Salts

Question3. Write one test apart from litmus test used to distinguish between an acid and a base.

3. Salts Remember the time when you went to a beach and played in the seawater? You surely must have complained about the seawater being too salty! Table salt is the same salt that is present in the seawater. In chemistry, we use the same term ―salt‖ to describe such substances. Salt is produced by the reaction of acid and base. Acid + Base Salt Question4. Give an example of a salt other than table salt.

Question5. What is a neutralization reaction?

We brush our teeth daily in the morning, but why do we do it?

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VII CBSE

Chemistry – Acids, Bases and Salts Explain the concept of neutralization and how is it used in the case of toothpaste.

Did you know? Why animals don’t need to brush daily is because they don’t eat cooked food. They eat raw food which needs a lot of chewing to digest it, thereby cleansing the teeth naturally

4. Visual Indicators What are the common ways to identify whether a substance is acidic or basic in nature?

Why do visual indicators show a change in color when introduced to an acidic or a basic medium?

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VII CBSE

Chemistry – Acids, Bases and Salts Magic Colour - Home activity Try this activity at home and over the course of the activity you will be able to visualize what universal indicators are. Materials Required  Universal indicator (available at chemical shop)  Lemon Juice  Liquid laundry detergent  Pain brush  Cotton swab  Water  3 Plastic cups  Paper towels  Pencil, Pen  Scissors  Teaspoon  Chemical safety

Procedure:  Trace the fish trout pattern on a piece of card  Pen the following names in the three plastic cups: Cup 1- Lemon juice Cup 2- Universal indicator Cup 3- Laundry detergent  Add lemon juice and laundry detergent to the cup according to the labels.  Place about 40 drops of universal indicator solution into the cup labeled as universal indicator  The colour of universal indicator is green. Use a paint brush to completely colour the fish with this green solution. There might be a slight change in colour as the solution reacts with the fish.  Let the coloured fish dry. Then dip a cotton swab in lemon juice and paint a few stripes, dots or other designs on the fish. Do not cover the entire fish with the designs. Observe what happens.  Now, dip a different cotton swab into the detergent solution. Paint some stripes or dots on the fish and compare with what happened when the lemon juice was used to make the designs.  Allow the fish to dry and observe what happens to the colours.  Thoroughly clean the area and wash your hands. What did you observe?  Universal indicator is green in colour.  Base- When laundry detergent is applied to it, it turns blue or purple.  Acid- When lemon juice is added it, it turns yellowish or orange. This activity shows how acids and bases change colour when indicator is added. This helps in identification of the presence of acid or base.

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VII CBSE Chemistry – Acids, Bases and Salts Question6. Summarize the properties of acids, bases and salts.

Acidity and basicity are two extremes of a property that describes chemicals, just like hot and cold are two extremes of temperature. Mixing acids and bases can cancel out their extreme effects much like mixing hot and cold water can even out the water temperature. A substance that is neither acidic nor basic is called neutral In chemistry, numeric scale is used to specify the acidity or basicity of an aqueous solution, which is called the pH scale.

Figure 1 - The pH Scale (label the diagram)

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VII CBSE

Chemistry – Acids, Bases and Salts

5. Application and Uses Why do we need to study acids, bases and salts? Acids, bases and salts are chemicals which we come across in our everyday life and studying them can help us understand them and subsequently use them better. Write some of the most significant application of acids and bases.

Question8. Why are bases used as fertilizers?

Question9. Why is base applied to the affected area in the case of a bee sting?

Question10. What interests you the most in this chapter? Write the importance of acids, bases & salts in our daily life.

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VII CBSE

Chemistry – Acids, Bases and Salts

Instructions Solve these problems after watching the videos. 1. What are the natural sources of the following acids?  Oxalic acid  Stearic acid  Tannic acid 2. Classify acids on the basis of their sources with help of examples. 3. Complete and balance the following equations:  NO2 + H2O → ___________ + ____________  P2O5 + H2O→ __________ + ____________ 4. Give reason: Curd is not stored in brass vessels. 5. Give two common uses of nitric acid. 6. Give reason: Vinegar should never be stored in a metal bottle? 7. What do you observe when vinegar reacts with sodium bicarbonate? 8. With the help of an example, explain the reaction of bases with salt solution. 9. Explain the importance of neutralization with regards to crop growth. 10. Explain how dyes synthesized from fruits and vegetables are used as indicators. 11. Classify the following substances as acids, bases and salts.  Oil of vitriol  Green vitriol  White vitriol  Caustic soda 12. What is the composition and use of aqua regia? 13. With the help of an example, show the action of an acid on metal carbonate and bicarbonate. 14. Give two uses of potash alum. 15. Explain how neutralization helps in disposal of factory wastes. 16. The turmeric strain on your shirt turns red when washed with soap: (a) due to the basic nature of soap (c) due to the neutral nature of soap (b) due to the acidic nature of soap (d) none of these 17. A natural source of ascorbic acid is: (a) Orange (c) Citrus fruits (b) Lemon (d) all of these 18. It is advised to rub a solution of baking soda on human skin when an ant stings as baking soda is: (a) neutral in nature (c) basic in nature (b) acidic in nature (d) none of these 19. Phenolphthalein is first added to some hydrochloric acid and then sodium hydroxide is added to the solution of phenolphthalein and hydrochloric acid. The color transition occurring during this is from_____________. (a) colorless to pink (c) red to blue (b) pink to colorless (d) blue to red 20. The solutions which do not change the color of either red or blue litmus solutions are known as: (a) neutral solutions (b) acidic solutions (c) basic solutions (d) none of these

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VII CBSE

Chemistry – Physical and Chemical Changes

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Physically, matter can be classified into three physical states. The physical aspects cover these states, the inter conversion and the changes it undergoes while transforming. But matter can also be classified by its chemical composition as:  

Pure substance Impure substance

2. Pure Substances (Purity) A matter composed of only one type of particle and having uniform composition is called pure substance. Question1. Is the pure milk that you get, really pure? Justify your answer.

Pure substance can be further classified into:  

Elements Compounds

a. Elements What are elements?

b. Compounds Question2. Why is water considered as a compound?

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VII CBSE

Chemistry – Physical and Chemical Changes

Figure 1 - Types of Pure Substances

Very few of the chemicals and substances we encounter on daily basis are in their pure form. Most of them are mixtures.

3. Impure substance A mixture is a combination of two or more pure substances in which each pure substance retains its individual chemical properties. Mixture can be composed of solid, liquids or gases. Mixture can be defined in numerous ways and is classified as 

Homogeneous mixture Heterogeneous mixture

Define the terms, ‘homogenous and heterogeneous mixtures’.

Question3. You have one glass of water and some sugar and sand. How will you create a homogeneous mixture?

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VII CBSE a. Solutions

Chemistry – Physical and Chemical Changes

Question4. Define the terms, solute and solvent. Mention the solute and solvent of a water-salt solution.

  

A homogeneous mixture of two or more substances, which may be solids, liquids, gases or any other combination of these. The particles should have dimension between 0 and 2 nanometers. Solutions are transparent, i.e. light can pass through it. Mixtures are stable and do not change after standing for long time

a. Colloids What are colloids?

Dispersion Medium

Dispersed Phase

Type of Colloid

Example

Solid

Solid

Solid sol

Ruby glass

Solid

Liquid

Solid emulsion/gel

Pearl, cheese

Solid

Gas

Solid foam

Lava, pumice

Question5. What are sols and emulsions?

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VII CBSE b. Suspensions

Chemistry – Physical and Chemical Changes

A suspension is a heterogeneous mixture in which solids are dispersed in liquids. The solute particles in suspension do not dissolve but remain suspended throughout the medium. Question6. Write the properties of a suspension.

Did you know? We all have experienced such a picture where we are able to see the path of light. Such a phenomenon occurs when light travels through a colloid. The phenomenon, known as the Tyndall effect, is light scattering by particles in a colloid or particles in a very fine suspension.

4. Concentration A complete description of a solution, it describes what the solute is and how much solute is dissolved in a given amount of solvent or solution. The quantitative relationship between solute and solvent is the concentration of the solution. This concentration may be expressed using several different methods.

Question7. How do you express concentration of a solute in solvent in terms of percentage?

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VII CBSE Chemistry – Physical and Chemical Changes 5. Physical and Chemical Changes Change is a rule of nature. As the saying we all observe and wonder many changes around us in our daily life. Change can be of many types, which we might not be aware of. When you add sugar to the water the sugar dissolves, this is also a change. Make a list of five changes that you observe around you in your daily life. Before Changes

After Changes

Now we have studied both the chemical and physical states of matter. There are several differences between the physical & chemical changes. a. Physical Change Changes wherein the molecule does not change its chemical makeup, but its physical appearance might be altered.

Figure 2 - Heat Leading to Larger Inter-molecular Space

b. Chemical Change

Question9. Would you term curd formation as a chemical change? Justify your answer.

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VII CBSE

Chemistry – Physical and Chemical Changes

Question10. Classify the following on the basis of whether they are a chemical or physical change. (a) Whipping of egg whites (b) Milk souring

(c) Dicing the potato

Did you know? Cooking is a process where both physical and chemical change occurs simultaneously.

Take an apple cut into two sections. Observe the exposed area immediately. After ten minutes observe what happens to the inside colour. The oxygen in air reacted chemically with the apple and caused a colour change. This is also chemical change because the colour of apple will not be able to change it again. Question12. Pour a quarter cup of vinegar into a clear plastic cup. Add a teaspoon of baking soda and observe bubbles are formed. Can you name the type of change?

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VII CBSE

Chemistry – Physical and Chemical Changes

6. Separation Techniques Heterogeneous and Homogeneous mixtures are separated using different techniques based on the type of mixture we are dealing with.

Did you know? One of earliest separating techniques was invented by farmers who separated husk from paddy. They allowed both of them to fall along the wind. Husk being lighter, was carried by the wind to a longer distance.

Sublimation Sublimation is a process of conversion of a solid into vapour or a vapour back to solid state, without passing through the liquid state.

Figure 3 - Separation Using Sublimation

Question11. What type of mixture can be separated by sublimation?

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VII CBSE a. Distillation

Chemistry – Physical and Chemical Changes

What is distillation? Which property of substances does this process use as a basis for separation of components of a mixture?

Figure 4 - Separation by Distillation

b. Centrifugation

Question12. Explain the method of centrifugation.

Any heterogeneous mixture containing an insoluble solid in a liquid can be separated by two methods  

Sedimentation Decantation

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VII CBSE c. Sedimentation

Chemistry – Physical and Chemical Changes

The insoluble solid substance in the solution settles down at the bottom of beaker and a clear liquid is obtained standing above the solute. This process is called sedimentation.

Figure 5 - Settling of Solute, Sedimentation

Question13. What do you understand by the process of decantation?

d. Chromatography Define chromatography. Explain the underlying principle involved.

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VII CBSE

Chemistry – Physical and Chemical Changes

Figure 6 - Separation of Components of Dyes (Chromatography)

 

Misconception: Passing any water through a water-purifier makes it fit to drink. Clarification: Water purifiers have special filters that keep back dust and impurities present as particles in the solution. But these water purifiers are unable to keep out any impurities that might be dissolved in the water. Speaking in simple terms, water purifier only purifies the water physically, leaving scope of chemical poisoning.

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VII CBSE

Chemistry – Physical and Chemical Changes

Instructions: Solve these problems after watching the videos. 1. What do you mean by a pure substance? 2. Are all compounds pure substances? Justify your answer. 3. What do you mean by a heterogeneous mixture? 4. In a homogeneous solution, the dimension of solute particles varies between: a. 0-2 nanometer b. 2-4 nanometer c. 4-6 nanometer d. 6-8 nanometer 5. Does light pass through a colloid without any deflection? 6. How is a suspension different from a colloid? 7. Is milk a colloid, suspension or true solution? 8. How will you separate a mixture of Iron filings and sand? 9. What is sublimation? Give examples of sublimable substances. 10. Explain the principle of distillation which is used as a separation method. 11. Explain the working of centrifugation separation technique? 12. What type of mixtures can be separated by sedimentation? 13. What do you mean by decantation? 14. A solution of water and sugar is an example of: a. Colloid b. Suspension c. True solution d. Pure substance 15. Mixtures of colored compounds can be separated by: a. Distillation b. Decantation c. Centrifugation d. Chromatography 16. What is the use of chromatography? Explain the principle behind it. 17. Light passes through _________ without any deflection. a. solution b. colloid c. suspension d. emulsions 18. What is meant by concentration of solution? 19. How will you separate a solution of oil and water? 20. You have two substances with a large difference in their weight. Which of the following technique is used for the separation of the mixture? a. Distillation b. Chromatography c. Sublimation d. Centrifugation

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VII CBSE

Chemistry – Water

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Why is water considered as the most vital compound for our survival?

Did you know? There is more fresh water stored under the ground in aquifers than there is on the earth’s surface.

Water is one of the major requirement for all forms of life without which the survival of life is practically impossible. The most important use of water that might come to our mind may be drinking, but do you know that only 1% of the water on earth is drinking water.

Question1. Why is water considered essential for survival of life? Give reasons.

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Chemistry – Water

2. Sources of Water When Neil Armstrong looked at Earth from the Moon, it appeared to him as a blue sphere! This is because water covers more than two thirds of the Earth's surface. But still, the fresh water that we can drink amounts to less than 0.5% of the total water on Earth Every day we use water for cooking, bathing, cleaning and drinking, but how often do we think about its source? Where does all this water come from? Question2. Name the various water resources that are available on Earth.

Water is continuously moving around the Earth and constantly changing its form. It evaporates from land and water bodies and is also consumed by all forms of life on Earth. Even though water is constantly moving and changing its form, its total quantity on Earth‘s surface is constant. Question3. By percentage, how much of the human body consists of water?

Question4. Is the water that you get for cooking and washing purposes fit for drinking? If not, how should we treat it?

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Chemistry – Water

Figure 1 - Distribution of Water on Earth

There are two main sources of water: surface water and ground water. Surface water comprises of water found in lakes, rivers, oceans and reservoirs. Ground water is found lying under the surface of land, where it travels through layers and fills up the openings in the rocks. The rocks that store and transmit groundwater are called as aquifers. Ground water must be pumped from an aquifer to the Earth's surface for use.

3. Water Depletion All the materials and energy essential for the survival and welfare of living beings, including humans, are provided by nature. But due to his unending greed, man has destroyed nature for his own convenience and has made himself the master of nature. On account of such ruthless exploitation, the human society has vastly modified the ecosystem in different parts of the world and has brought undesirable changes in various natural habitats. Did you know? The World Water day is marked on 22nd March every year. It's a day when people across the globe spread awareness about the depletion and pollution of water and other water related issues. Join the movement, spread awareness and make a difference.

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VII CBSE

Chemistry – Water

Question5. Write the causes for water depletion.

2. Effects of Water Depletion Water is the one of the most important element of our biosphere which is essential for the existence of all forms of life. Water is precious, but are we aware of this? The water present under the surface of the Earth, known as ground water, is what we extract for our day to day purposes. This storing of ground water occurs over large periods of time with the passage of water molecules through the intermolecular spaces between the soil, rock, sand and gravel particles. The downward flow of water stops when it catches the rock. These water molecules which get collected is of good quality and it can be used for drinking. But this underground water source is slowly getting depleted due to over use of pumping, bore well, dug wells, etc.

Figure 2 - Water Depletion

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VII CBSE Chemistry – Water Question6. How can you prevent ground water depletion?

Question7. What can we do to save water from pollution?

3. Water Management What do you understand by water management?

We have come up with various methods to conserve water, which are reliable and can be easily adopted but the real problem lies with its execution. These methods can help preserve water at household levels and also at industries. The main problem that we are facing is that not enough of us are aware about the depletion and pollution of water. Did you know? It takes around 700 gallons of water to make a cotton shirt, and 2,600 gallons to make a pair of jeans — most of them to grow the cotton.

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VII CBSE Chemistry – Water Question8. Mention any one method for conservation of water and how the conserved water can be used?

Question9. What are the causes of water pollution and how do they contribute to water depletion?

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VII CBSE

Chemistry – Water

Instructions: Solve these problems after watching the videos. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

17.

18.

19.

20.

What is the relative molecular mass of water? Write two important uses of water. Classify natural water based on its degree of impurity. Explain the importance of water cycle in our nature. Briefly explain the different types of impurities found in water. Give two uses of distilled water. Explain electrolysis of water in brief. Give reason: Sea water does not freeze easily as compared to pure water. Give reason: Water acts as a cooling agent. Explain how anomalous expansion of water plays an important role in the sustenance of aquatic life in cold places. Why water is often referred to as a universal solvent? With the help of an example, explain the reaction of water with a metal. Differentiate between temporary hard water and permanent hard water. Briefly explain three causes of water pollution. Give some measures by which we can save water. Plants give out water in ________ state of matter: a) vapour b) solids c) liquid d) gaseous Which among the following is not a natural source of water? a) Ponds b) Canal c) River d) Rains An example of water in its purest form is __________. a) sub soil water b) lake water c) rain water d) spring water During purification of water to obtain adequate quantity of portable water, which among the following steps is carried out first? a) Filtration b) Sedimentation c) Aeration d) Sterilization Water scarcity is experienced widely during which of the following seasons? a) Winter season b) Autumn season c) Spring season d) Summer season

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VII CBSE

Biology – Nutrition in Plants

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Question1. What do you mean by being alive?

Living organisms exhibit certain characters which make them unique and differentiate them from non-living things. It is a unique and complex organization of molecules expressing it through chemical reactions, which lead to growth, development, responsiveness, adaptation and reproduction. Cells are the basic structural and functional units of life. Cells comprise of many organelles such as nucleus, endoplasmic reticulum, etc. to carry out different life functions. a. Classification of Living Organisms The process of obtaining food and utilizing it is called nutrition. A nutrient can be defined as a substance which an organism obtains from its surroundings and uses it as a source of energy or for the biosynthesis of its body constituents. There are mainly two modes of nutrition – autotrophic and heterotrophic. Question2. Differentiate between autotrophic and heterotrophic nutrition.

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Biology – Nutrition in Plants

2. Photosynthesis During photosynthesis light energy is converted into chemical energy and is stored in the form of sugar. Light energy is trapped by chlorophyll and with the help of carbon dioxide, carbohydrate is prepared. This process occurs in plants and some algae. Plants need only light energy, CO 2 and H2O to make sugar. The process of photosynthesis takes place in the chloroplasts. The total energy fixed is around 1 % of the total energy available. The gaseous exchange in plants takes place through tiny pores, present on the surface of leaves, called stomata.

Figure 1: A. Stomata closed

B. Stomata open

Question3. Label the given diagram of cross section of a leaf.

Figure 2: Cross - Section of a Leaf

EquationSunlight 6CO2 + 6H2O

__________________ Chlorophyll

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+

6O2

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VII CBSE

 

Biology – Nutrition in Plants

Misconception: Release of oxygen during photosynthesis is due to break down of CO2 molecule. Clarification: In photosynthesis light is used to split hydrogen from water and uses it to change carbon dioxide into a simple carbohydrate. The byproduct is oxygen, which is released as gas. Some bacteria can perform the same thing using hydrogen sulphide. Heat energy is used to drive this process. The byproduct is pure sulphur and is probably the source of most of this mineral. It is thought that the first forms of life on earth used geothermal energy to make carbohydrates using hydrogen sulfide and carbon dioxide. This process still continues deep underground and at the bottom of the ocean around hydrothermal vents.

Question4. How will you prove that chlorophyll is required for photosynthesis to take place?

Question5. Why dark reaction is called dark reaction?

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VII CBSE

Biology – Nutrition in Plants

Question6. There are some leaves which do not have green colour. How do they prepare their food?

Question7. In case of cactus plants the leaves are modified into spines. Why is it so? And how do these plants fulfill their nutritional requirement?

3. Other Mode of Nutrition Along with carbohydrates which are synthesized during photosynthesis, plants require some other nutrients as well. Such as nitrogen, phosphorus, potassium, calcium etc. the nutrients that are required in large amount are called macro nutrient. Soil is the source of nutrient for these plants. In case these nutrients are not present in sufficient amount plants adopt for some other ways for it. Let‘s discuss these ways in detail. (i) Saprophytic Nutrition In this type of nutrition, an organism lives upon dead organic sources such as dead plants and dead animals. These usually secrete digesting enzymes on food and absorb the liquidified molecules so formed e.g.; yeast, bread moulds and dung moulds etc.

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VII CBSE Biology – Nutrition in Plants Question8. When a slice of moist bread is kept in open for few days‘ fungal growth is observed as shown in the following diagram. From where does this fungus come on the bread slice?

Figure 3: Growth of Fungus on a Bread Slice

(ii) Parasitic Nutrition In this type of nutrition, an organism lives totally at the expense of other and derives its food material and shelter from the other organism. These organisms which derive food material are called parasites and the organism from which food is derived is called a host. This type of nutrition is termed as parasitic nutrition.

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Biology – Nutrition in Plants

Question9. Rafflesia arnoldii, the world‘s largest individual flower, is kind of nasty. Found in the forests of Malaysia and Indonesia, its giant red-brown blossom is nearly 1 meter (3.3 feet) in diameter and weighs up to 11 kg (24 pounds). It cannot photosynthesize; it depends on nutrients that it steals from the roots of neighboring Tetrastigma vines. Identify the host and the parasite in this relationship.

Figure 4: Rafflesia Flower

(iii) Insectivirous Plants Question10. Pitcher plant and venous fly trap can photosynthesize but still they trap insects and digest them hence, they are called insectivorous plants. What is the need for adapting to this kind of nutrition by these plants?

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VII CBSE Biology – Nutrition in Plants 4. Nutrients Being Replenished in the Soil Plants use the nutrients present in the soil as a result the amount of nutrient keeps depleting in the soil. So, it is needed that these nutrients are replenished in the soil either naturally or artificially. Nitrogen is one of the major nutrients required by the plants for synthesis proteins. Plants cannot use atmospheric nitrogen directly. Question11. Why do farmers use fertilizers?

Question12. Given below is the picture of root nodule in leguminous plants. Explain its significance for the plant.

Figure 5: Root Nodule

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VII CBSE

Biology – Nutrition in Plants

Instructions: Solve these problems after watching the videos. 1. Which of these components of food can be synthesised by plants? a. Carbohydrates c. Fats b. Proteins d. All of these 2. Which gas is released during photosynthesis? a. SO2 b. CO2 c. NO2 d. N2O 3. Amarbel is an example of a. Autotroph c. Saprotroph b. Parasite d. Host 4. Nitrogen of the atmosphere is absorbed by a. Autotrophs c. Insectivorous plant b. Leguminous plants d. None of these 5. Which of these is not an insectivorous plant? a. China rose c. Pitcher plant b. Mistle toe d. None of these 6. Why are algae green in colour? 7. What is a host and parasite relationship? 8. How can you test the presence of starch in leaves? 9. Why is it said that whether directly or indirectly all living things depend on green plants for food? 10. Can we call an insectivorous plant as carnivorous? Why or why not? 11. Why is the number of stomata more on the lower side of leaves? 12. Write the function of spines of cactus. 13. Why do plants need nutrition? 14. Which is the ultimate source of energy? 15. What is the end product of photosynthesis? 16. Differentiate between parasite and saprophyte. 17. What is the mode of nutrition in fungi? 18. How are nutrients replenished in soil? 19. What is the function of stomata? 20. What grows on a moist piece of bread?

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VII CBSE

Biology – Nutrition in Animals

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Question1. What will happen if you are kept on fast for a number of days? Give reason for your answer?

a. Calorie A calorie is defined as the amount of energy needed to raise the temperature of 1 g of water by 1 °C. In a popular use of the term calorie, dietitians loosely use it to mean the kilocalorie, sometimes called the kilogram calorie, or large Calorie (equal to 1,000 calories), in measuring the calorific, heating, or metabolizing value of foods.

b. Components of Food and Their Function The food which we eat has different components. These components of food that an organism uses to survive and grow are called nutrients. Question2. Match the following.

i. ii.

Nutrients Carbohydrates Proteins

iii. iv. v.

Fats Vitamins Minerals

vi.

Roughage

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Function a. Body building food b. Necessary for growth and development of bones and teeth c. Add bulk to our food d. Helps in removal of waste e. Needed for proper growth and good health f. Energy bank

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VII CBSE Biology – Nutrition in Animals Other than these six our body also needs substantial amount of water. Water is required for a number of functions - it helps in transport of nutrients, regulation of body temperature and eliminating waste from the body.

2.

Different ways of taking in Food Recall different organisms in your surroundings, do they all eat food in same way as you do? The answer will be an obvious ‗no‘. This mode of taking in food depends upon a number of factors such as the environment in which they live, availability of food etc. for example a spider wraps the insect in their spider silk which is what the web is made from. Then the spider injects the insect with venom that either paralyzes or kills the insect. Then the spider eats it.

Question3. How the following organisms take their food? 1. Snake

2. Frog

3. Humming bird

4. Human infants

3.

Nutrition in Humans Human beings have holozoic mode of nutrition. They take solid food in and this food is gradually digested as it moves down the alimentary canal. The alimentary canal is basically a long tube extending from the mouth to the anus. Various parts of alimentary canal are specialized to perform different functions. Let‘s see this process in detail. The process of digestion takes place in four different stages – Ingestion, Digestion, Absorption and Egestion.

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VII CBSE Biology – Nutrition in Animals Question4. Label the different parts of digestive system given below.

Figure 1: Digestive System in Humans

a. Mouth The mouth is the first site of digestion. The role of the teeth, tongue and saliva is to break down food into smaller particles which are more manageable to digest. Digestion begins at the mouth itself. Smell and taste are senses intimately related to digestion. Taste and smell help us distinguish food that is good to eat from poisonous and spoilt food. Moreover, these senses help in signaling the brain about the arrival of food so that it can prepare the rest of the digestive system to receive food. Question5. How is the sense of smell important to our sense of flavour?

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VII CBSE (i)Teeth

Biology – Nutrition in Animals

The intake of food is followed by breaking the food into small pieces by the process of chewing. The chewing machinery of the human body includes the teeth, supporting muscles and saliva. Humans have two sets of teeth- Milk teeth or deciduous teeth and permanent teeth. Humans along with most of the mammals have different types of teeth.

Figure 2: Different Types of Teeth

Question6. Match the following. Type of teeth

Function

(i) Incisors

(a)Tearing

(ii) Canines

(b)Grinding

(iii)Premolars

(c)Chopping

(iv)Molars

(d)Crush and chew

Question7. Label the parts of teeth given below.

Figure 3: Parts of Teeth

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VII CBSE (ii) Saliva

Biology – Nutrition in Animals

The next thing that food encounters in the mouth is saliva. Saliva is a viscous mixture of water and electrolytes secreted by salivary glands. It is slightly acidic with a pH of 6.8 and contains salivary amylase and lysozyme (antibacterial) enzymes. Question8. Justify this statement ―Digestion of food begins in the mouth‖.

Question9. Rice is a rich source of starch and iodine gives blue black colour with starch. If you add iodine solution to chewed rice, what colour will it give?

(iii)Oesophagus Saliva along with the action of teeth aids in the formation of circular masses of food particles called bolus which can then easily enter the oesophagus or food pipe. Food then moves down the oesophagus by involuntary, alternate contraction and relaxation of muscles called the peristalsis.

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Figure 4: Peristalsis in Oesophagus

b. The Stomach The stomach‘s primary role is to break down food into even smaller chunks, destroy bacteria and begin the process of chemical digestion. Its digestive enzymes help in breakdown of food and provide an environment to help in that process. The stomach walls release gastric juices containing enzymes and hydrochloric acid as well as mucus from structures called pits. The stomach is lined with muscles to produce strong contractions that can mix the food with gastric juices. The enzymes are secreted in an inactive state in the stomach. Question10. Why do you think it is necessary for the stomach to close its openings at both ends during digestion?

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Question11. Why is protein digesting enzymes in the stomach released as inactive enzymes or zymogens?

Question12. Why the acid in stomach does not digest the stomach itself?

Did you know? A man with a hole in his stomach provided a window into digestion. In 1822, a fur trapper accidentally shot a 19 years old man named Alexis St. Martin. Army surgeon William Beaumont successfully patched up St. Martin, but he was left with a hole in his stomach's abdominal wall, which is called a fistula. The fistula allowed Beaumont to investigate the workings of the stomach in entirely new ways.

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VII CBSE c. The Small Intestine

Biology – Nutrition in Animals

The small intestine is almost 10 feet long but only 1 inch thick. Its main function is to digest and absorb nutrients. The structure of the intestine optimizes this function. The digestion in the small intestine is aided by secretions of the pancreas and liver. Secretions from liver are stored in the gall bladder before being released into the small intestine. The small intestine‘s internal surface is covered by bumps known as villi. Each villus is in turn covered by microvilli. The liver plays a role in packaging and segregating absorbed nutrients. It also repurposes enzymes and gastric juices absorbed in the intestine.

Did you know? Laundry detergents take cues from the digestive system. Laundry detergents often contain several different classes of enzymes, including proteases, amylases and lipases. The human digestive system also contains such enzymes.

Question13. What do you mean by accessory digestive glands? Name the accessory digestive glands found in your body.

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VII CBSE Biology – Nutrition in Animals Question14. Bile and pancreatic juices change the pH of the chyme in small intestine. What change occurs in the pH? Can you explain the requirement of changing the pH from the perspective of enzyme requirements?

Question15. How do microvilli help in the process of digestion?

d. The Large Intestine The large intestine performs the final absorption of nutrients and water. Water is reabsorbed from the chyme to make it more semisolid and easy to defecate. The chyme in the large intestine is called faeces. The large intestine also stores the faeces so that it can be defecated at one go.

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Did you know? Flatulence gets its smell from bacteria. Intestinal gas, or flatus, is a combination of swallowed air and the gases produced by the fermentation of bacteria in the gastrointestinal tract. The digestive system cannot tract, and makes their way into the large intestine. Hordes of intestinal bacteria get to work, releasing a variety of gases in the process, including carbon dioxide, hydrogen, methane and hydrogen sulfide (which gives flatulence its rotten-egg stench).

Question16. Do you think the microorganisms in the large intestine have a role other than producing odour in the faeces?

Question17. Which part of the large intestine stores faeces?

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4. Nutrition in Grass Eating Animals You must have noticed that grass eating animals keep on chewing something. They do this to digest cellulose as their diet mostly contains leaves of plants which are rich in roughage. The grass eating animals digest their food in two steps. Their stomach is divided into four chamber the __________________________, _____________________, _____________________________ and _____________________.

Question 18. Label the parts of digestive system of cow in the given figure.

Figure 5: Digestive System in Grass Eating Animals

The half chewed food is swallowed and it then goes from mouth to the rumen. Here, bacteria act on food and digest the cellulose. This half-digested food sent to the second muscular chamber; the reticulum. From the reticulum the food is sent back to the mouth as cud. Chewing of the cud is called rumination and such animals are called ruminants. Cow, goat, buffaloes, sheep, bison, etc. are good example of ruminating animals. The re-chewed food is swallowed for the second time. After passing the first two chambers it enters the third chamber; the omasum. Here the food is further broken down into smaller pieces and finally enters the fourth chamber, the abomasum. Here, all enzymes act upon the food and the digestion is completed.

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5. Nutrition in Amoeba Amoeba is a unicellular animal, so it doesn‘t have a mouth for ingestion of food. Amoeba ingests the food by encircling it with the help of pseudopodia. When the food is completely encircled, the food is engulfed in the form of a bag called food vacuole. Several digestive enzymes react on the food present in the food vacuoles and break it down into simple and soluble molecules. The food digested by digestive enzymes is then absorbed in the cytoplasm by the process of diffusion. The food absorbed by the cytoplasm is used to obtain energy, growth and repair. Undigested food in the food vacuole is thrown out of the body by exocytosis. Question19. Identify the different stages in digestion of amoeba.

Figure 6: Different Stages in Nutrition of Amoeba

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Instructions: Solve these problems after watching the videos. 1.

The walls of the large intestine absorb a. Cellulose c. Proteins b. Water d. Digested food 2. Fat is completely digested in the a. Stomach c. Mouth b. Small intestine d. Large intestine 3. The first four teeth in each jaw are called a. Canines c. Premolars b. Molars d. Incisors 4. The function of the digestive juices present in the stomach is to breakdown a. the proteins into simpler substances c. Fats into juices b. Starch into sugars d. Food into gases 5. The largest gland in the human body is a. Oesophagus c. Liver b. Salivary gland d. Villi 6. Why does bread taste sweet when chewed for some time? 7. Which acid is present in the stomach? Why does it not harm our own body? 8. Pancreas is a part of our digestive system. Justify 9. What is the function of the salivary amylase? 10. Where is the bile produced? Which component of the food does it digest? 11. Can we survive only on raw, leafy vegetables/grass? Discuss. 12. Why do we get instant energy from glucose? 13. Write one similarity and one difference between the nutrition in amoeba and human beings. 14. Which carbohydrate can be digested by ruminants but not by humans? 15. Large intestine is longer than the small intestine. (True/False) 16. Villi are present in the large intestine. (True/False) 17. What are the simplest digestive products of carbohydrates, fats and proteins? 18. Name the sphincter which regulates the exit of food from the stomach. 19. Why do different animals have different types of digestive systems? 20. What is the difference between defecation and excretion?

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VII CBSE

Biology – Transportation in Animals and Plants

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Humans and plants require oxygen, food, water and nutrients for their various life processes. Transportation system carries these substances to all the cells, collect wastes from the cells and deposit it in the parts from where they can be removed. The systems involved in the process of transportation of substances are _______________ and____________________.

2. Circulatory System It is the system which carries out the transportation of various substances throughout the body. Question1. When you are injured, a red liquid starts coming out of the injured part. What is this liquid?

The transportation of nutrients, carbon dioxide, oxygen, enzymes, hormones and waste products is carried out by two major fluids in our body – blood and lymph. Let us now discuss about the various components of the circulatory system in humans.

a. Blood Blood is a constantly circulating fluid providing the body with nutrition, oxygen and waste removal. The fluid part of blood is __________. Another important component of blood is red blood cell. Its main function is ___________________________. It is red in colour due to the presence of _______________. The ability of blood to reach the corners of our body aids in the repair of cells and defense of body against microorganisms. These cells which protect our

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VII CBSE Biology – Transportation in Animals and Plants body against disease causing germs is white blood cells. When we get injured, blood stops coming out of the wound after sometime. This is due to clotting which occurs due to the presence of _____________. Question2. Write about the characteristic features and functions of the fluid part of the blood?

Did you know? Crabs and lobsters have a pigment called haemocyanin instead of haemoglobin because of which their blood is blue instead of red.

b. Blood Vessels Unlike lower creatures which have open circulatory system, we humans have a well-defined network of closed channels for carrying the blood around. These channels are called blood vessels. The two main types of blood vessels are arteries and veins. (i) Arteries – They carry oxygen rich blood from the heart to all parts of the body. (ii) Veins- They carry carbon dioxide rich blood from all parts of the body back to the heart.

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Question3. When we are asked to make a coloured diagram of arteries and veins, we usually make arteries red and veins blue. Why is it so? Is the colour of blood that flows in veins blue?

The arteries on reaching the tissues, break down into smaller vessels called arterioles. They also help in regulation of blood flow. The arterioles further branch to form capillaries which are the narrowest vessels. They help in the exchange of gases as diffusion is easy through their thin membrane. The capillaries then lead to comparatively thicker vessels called the venules. These are almost as narrow as the arterioles but have comparatively thinner walls.

Figure 1: Blood Vessels





Misconception: Arteries are usually defined as vessels which carry oxygenated blood and veins are usually defined as vessels which carry deoxygenated blood. Clarification: Arteries are the vessels which carry blood away from the heart and veins are the vessels which carry blood to the heart. Most of the arteries carry oxygenated blood except pulmonary artery, which carried deoxygenated blood from the heart to the lungs. Similarly, most of the veins carry deoxygenated blood except pulmonary vein which carries oxygenated blood from the lungs to the heart.

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c. Heart It is the pumping organ of the body. This organ along with the blood vessels makes up the circulatory system. We human beings have a four chambered heart which is important for avoiding the mixing up of oxygenated blood with deoxygenated blood. Our heart consists of two atria and two ventricles. The atria form the upper chambers and the ventricles form the lower chambers. Our heart __________ while receiving blood and ___________while pumping blood. Question4. Label the following diagram correctly.

Question5. Explain the process of circulation of blood in the heart and in the body.

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Our body has valves to keep the flow of blood unidirectional. The opening and closing of these valves make the rhythmic lub - dub sound. Stethoscope is used by doctors to listen to the heartbeat.

Did you know? Our heart pumps about 5000 litres of blood in an hour and we have just 5 litres of blood in our body.

d. Pulmonary Circuit Pulmonary system consists of the right side of the heart which is involved in the oxygenation of the blood. It receives deoxygenated blood from the body and sends it to the lungs to pick oxygen and release carbon dioxide. This circulation from right side of heart to lungs and back to the heart completes the pulmonary circuit. The exchange of gases in the lungs takes place in the balloon shaped structures called_______________.

e. Systemic Circuit Blood that comes from the lungs is received by the left side of the heart and then circulated to the rest of the body. This circulation from the left side of the heart to the body cells and back to the heart completes the systemic circuit. Both pulmonary and systemic circulation results in double circulation of blood in the body.

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Biology – Transportation in Animals and Plants Figure 2: Double circulation

Question6. What happens in a heart attack?

f.

Pulse When the heart pumps blood, it moves into the arteries with pressure. This causes the arteries to expand creating a pulse. We can feel this when we touch our wrist or neck. It is felt only at a few places of our body because arteries are usually buried deep in our body. The number of times the heart beats per minute is pulse rate. Pulse rate in a normal resting person is _________________beats per minute.

Activity: Gently place two fingers of your right hand on the inside of your left wrist, below your thumb. When you feel your pulse, count the number of beats in 15 seconds. Multiply this number by 4 to calculate your beats a minute.

Question7. Write about the mechanism of transportation of substances in the organism shown in the picture below.

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3. Transportation in Plants Plants require a transportation system to transport the components required for photosynthesis to the specified site; also to carry the food produced to different parts of the plant. Plants take in water and nutrients by a process called osmosis. In this process, water moves from a region of its _____________concentration to a region of its ______________concentration. Vascular tissues are present in plants for the transportation purpose. These tissues comprise of xylem and phloem. Question8. Write the functions of xylem and phloem.

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Question9. Phloem cells provide a passage for two way movement of food- both downwards and upwards. What is the need to transport the food in upward direction?

Xylem Vessel

Phloem Vessel

Figure 3: Vascular Tissues

Question10. If a potted plant is covered with a glass jar, water vapours appear on the wall of glass jar. Explain why?

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Another process in which water moves up in plants is transpiration. In this, water is lost as vapours from the aerial parts. This creates a suction force due to which more water is pulled up by the tubes of xylem to the leaves to replace the water that is lost.

Figure 4: Transpiration

Question11. Why do you feel comfortable when you sit under a tree in a hot summer afternoon?

Question12. Compare the transportation process in humans and plants.

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4. Excretory System During the various life processes carried out in our body, a number of waste products are generated. The removal of these metabolic wastes from the system is known as excretion. Humans have a specialized excretory system to carry out excretion. The major waste products are carbon dioxide, faeces and urea. The human excretory system is made up of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra. Various nitrogenous wastes like urea or uric acid are removed from the blood in kidneys.

Question13. Label the following diagram of human excretory system.

Nephrons form the basic unit of filtration in kidneys. Kidneys eliminate the nitrogenous waste from the body in the form of urine. The urine formed in the kidneys undergoes various levels of filtration as it passes through the nephron. Various useful substances like glucose, amino acids and salts are absorbed from the urine by the tubes in nephrons. The urine thus formed at the end is passed on to the _________ and then stored in the urinary bladder until the bladder is full and we get the urge to urinate. In case of kidney failure, we need treatment to replace the work our kidneys used to do. Unless we have a kidney transplant, we will need a treatment called dialysis. In dialysis, the patient‘s blood is lead from the radial artery in his arm through the machine where urea and excess salts are removed and the purified blood is returned to a vein in the same arm.

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Question14. Fill in the table with appropriate words.

Structures

Functions

Ureters Urinary Bladder

Urethra

Question15. Write the main excretory product in the organisms given below.

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Biology – Transportation in Animals and Plants

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Instructions: Solve these problems after watching the videos. 1. How many chambers does the heart have? a. One c. Three b. Two d. Four 2. Why does blood turn dark red as it circulates through the body? a. It starts to clot b. It gets old and dirty flowing through the body c. The oxygen in it is replaced with carbon dioxide d. The farther blood is from the heart, the more dark red it is 3. The watery part of the blood is: a. Veins c. Plasma b. Platelets d. RBCs 4. Blood that returns to the lungs from the body is: a. Oxygenated c. Mixed b. Deoxygenated d. None of these 5. Water absorption through roots can be increased by keeping the plants: a. In shade c. Under the fan b. In dim light d. Covered with a polythene bag 6. What makes the blood look red? 7. What are the four blood groups found in humans? 8. Why do animals like sponges and hydra do not possess a circulatory fluid like blood? 9. How the urine is removed from the body? 10. Why is transport of materials necessary in plants and animals? Explain. 11. What is the use of stethoscope? 12. Is clotting of blood dependent on exposure of blood to air? 13. Is there any relationship between the size of the body and rate of heartbeat? If yes, how? 14. Why do we urinate fewer times in summer than in winter? 15. How are kidney stones formed? 16. What is dialysis? 17. Why is the excretory product different in different animals? 18. Why do we need blood vessels? 19. What is pulse rate? 20. What is the difference between arteries and veins?

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VII CBSE

Physics – Light

Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction a. What is Light? Question 1. Alex argued that light is not necessary for seeing objects, rather our eyes are. Do you agree with him?

We humans are lucky to have the sense of vision. We see the beauty of nature around us, wonder at the various creations – it is all because of light. Light is a form of energy, which enables us to see objects around us. We are able to see objects around us when light from it reaches our eyes. This light can be produced by the body itself or can be produced by something else. So we can say that having eyes alone cannot ensure vision. Presence of light is also necessary. That is why we are unable to see anything in a dark room. Light is a very fast traveler. The speed of light in vacuum is about universal constant and is denoted by letter ‗c‘.

m/s. It is a

Did You Know? If the sun were suddenly snuffed, we on Earth would not notice until 8 minutes and 17 seconds – the time it takes sunlight to reach Earth.

b. Sources of Light An object that is capable of giving out light is known as a source of light. Broadly the sources of light can be classified as – Natural and Man-made or artificial.

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Question 2.Which of the following is a source of light? If they are then, classify them following as natural or man-made source of light.

Natural Source of Light

Artificial Source of Light

A body that emits its own light is known as a luminous body; else it is called nonluminous body.

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Question 3.Can a body be luminous at some point of time and non-luminous at others?

Question 4. A luminous body emits light of its own that enables us to see them. How is it possible to see the non-luminous bodies, which don‘t emit any light?

Did You Know? Humans are bioluminescent from metabolic reactions, but our glow is 1,000 times weaker than the naked eye can register.

Any medium through which light can pass partially or completely is called an optical medium. Based on how light behaves when it falls on a medium, materials can be classified as transparent, translucent and opaque.

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Physics – Light

Material

How light passes through it?

Transparent

Translucent

Examples

Glass, Water

Partially

Opaque

c. Rectilinear Propagation of Light

To explain various phenomena involving light, we take the path along which light travels as a ray. A large number of rays, moving in one direction, form a beam of light.

Parallel Beam

Divergent Beam

In a given medium, light travels in a straight line. This property is known as rectilinear propagation of light.

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Question 5.Using the figure below as a hint, explain the experiment to demonstrate rectilinear propagation of light.

d. Pinhole Camera

A pinhole camera is a device, which can help us to understand the rectilinear propagation of light.

Figure 5: Pinhole Camera

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Question 6.How does a pinhole camera work?

Characteristics of image formed:  Real image i.e. formed on a screen  Inverted image  Generally smaller Magnification is the ratio of the size of the image to that of the object.

i.e.

e. Shadow When an opaque object is placed between a light source and a screen, the passage of light is blocked. The dark patch thus formed is called shadow of the opaque object.

When there is a point source of light, umbra region (completely dark) is formed. Whereas for extended sources both umbra and penumbra (partially dark) regions are formed.

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Figure 6: Shadow due to Point Source

Penumbra is that region around the umbra where the shadow is only partial, or imperfect. You get these when the light source is larger than a single point. These form because the shadowing object blocks some of the light from the source, not all of it does. If you are in the penumbra looking towards the light source, you will see part of it visible, and part of it blocked. Point light sources will either be all visible or all blocked, but an extended source can be partially viewable beyond the edge of the shadowing object. The same is true of multiple sources.

Figure 7: Shadow due to Extended Source

f. Eclipse An eclipse is the partial or complete hiding of one heavenly body by the shadow of another. In this chapter, we are going to focus on lunar and solar eclipse. Lunar Eclipse: When the earth is between the sun and the moon

Figure 8: Lunar Eclipse

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Question 7.How is a solar eclipse formed? Explain with a diagram.

Now that we have a fair idea of light, let us examine reflection of light in details.

2. Reflection of Light Question 8.What possibilities can arise when a light beam strikes a surface?

a. Reflection and Laws of Reflection The phenomenon of bouncing back of light, when it hits a surface is known as reflection of light. From the earliest recorded history, humans have been fascinated by reflections. People were bewitched by their own reflection in a pool of water and reflections were so extraordinary that magic powers were ascribed to mirrors in fairy tales.

Figure 9: Reflection of Light

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VII CBSE Physics – Light Question 9.We all know that mirrors reflect light falling on them. But do other objects like table, chair also reflect light? Give proper reasons.

This phenomenon of reflection of light was found to obey two rules or laws.

Question 10.What is the two laws of reflection?

Did You Know? There is a phenomenon called the photic sneeze reflex, which causes uncontrollable sneezing in the presence of bright light. It affects roughly 18-35% of the human population, though nobody is sure why? One suggested cure: Wear sunglasses.

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VII CBSE Physics – Light Question 11.What happens to a light ray that is incident normally on a surface? What are the angle of incidence and the angle of reflection?

b. Types of Reflection There are two types of reflection:  Regular reflection

Figure 10: Regular Reflection



Irregular/Diffused reflection

Figure 11: Diffused Reflection

 

Misconception: The laws of reflection don’t hold true for diffused reflection. Clarification: Laws of reflection are always valid – be it regular reflection or diffused reflection.

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3. Images a. Plane Mirrors An image is an optical reproduction of a body. It is formed when rays of light, which originate from a point, meet again at another point. Mirrors form images of bodies placed in front of it. The most commonly used mirror is plane mirror, which has a plane-polished surface.

Did You Know? Only a few animal species have been shown to have the ability to recognize themselves in a mirror, most of them being mammals!

There are two types of images that can form after reflection from a mirror: real image and virtual image. Question 12.How does a real image differ from a virtual image?

Real Image

 

Virtual Image

Misconception: A shadow is an image (reproduction) of an object. Clarification: A shadow is not an image, but absence of light.

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Figure 12: Image Formation by a Plane Mirror

Characteristics of image formed by a plane mirror:  At same distance from mirror as the object  Same size  Erect  Virtual Question 13.Why is it so that if you can see another person in a mirror, he/she can also see you?

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4. Right or Left! The image produced by a plane mirror is horizontally inverted - that is reversed left to right. Look at yourself in a plane mirror and raise your right hand - your image raises its left hand. This is called lateral inversion. But why is it that the image is flipped only horizontally but not vertically?

Question 14.What is the cause of lateral inversion?

Question 15.A famous artist and scientist, Leonardo da Vinci, hid all of his ideas and inventions by writing all of his work backward. Use your mirror to decipher Leonardo‘s secret code:

Now that we have seen reflections in case of a plane mirror which was quite simple, let us complicate things and see the kind of images formed due to curved kind of mirrors.

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5. Spherical Mirrors Spherical mirrors are broadly classified as – Concave mirrors and Convex mirrors.

Figure 13: Types of Spherical Mirrors

Concave mirror is also known as converging mirror and convex mirror is also known as diverging mirror.

Figure 14: Focus of Spherical Mirror

Question 16. What do you mean by ―focus‖ of a spherical mirror?

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Nature of Image

Concave Mirror

If object is placed close, virtual, erect and enlarged image is formed.

Else real and inverted image is formed.

Convex Mirror

Virtual, Erect and Diminished image is formed.

Question 17. Give some applications of concave and convex mirrors.

6. Lenses A lens is a transparent medium, usually made up of glass or plastic. When light enters from one transparent medium to another, it bends. This is known as refraction of light.

Figure 15: Types of Spherical Lenses

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Did You Know? Lenses don’t always have to be made of plastic or glass. In the 1700s, spherical glass bottles filled with water were used to focus candlelight for fine work such as lace making, surgery etc.

A concave lens is also known as a diverging lens, while a convex lens as converging lens. This bending of light happens due to the fact that light has different speeds in different media.

Figure 16: Focus of Spherical Lens

Spherical Lens

Convex Lens

Concave Lens

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7. Does Sunlight Have Colors? We all have mesmerized at the beauty of rainbows. Ever wondered how a rainbow is formed? Rainbow is formed when white light passes through water droplets suspended in atmosphere (under certain conditions) and split into seven colors. Similar results are seen when white light passes through a prism. When it passes through a prism, it is separated into its component colors – Violet, Indigo, Blue, Green, Yellow, Orange and Red (VIBGYOR). Violet bends the most while red the least. This phenomenon is known as dispersion of light.

Figure 13: Dispersion through a Glass Prism

Question 18. Does the prism produce these colors? If yes, how does it produce? If no, then how is the band of colors obtained?

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Instructions: Solve these problems after watching the videos. 1) 2) 3) 4) 5) 6) 7) 8) 9)

How do we see objects around us? What do you mean by reflection of light? What are the two laws of reflection? At night, we get light from the moon then why isn‘t it considered as a luminous body? Why don‘t letters like A, H, V show lateral inversion? How does regular reflection differ from irregular reflection? What are the necessary conditions for a shadow to be formed? Demonstrate an activity using which you can verify rectilinear propagation of light. What are the advantages and disadvantages of using a pinhole camera? What do you mean by partial lunar eclipse and total lunar eclipse? Explain with a well labeled diagram. 10) Using a diagram show the characteristics of an image formed by a plane mirror. 11) What do you mean by dispersion? How can you show that sunlight is made up of seven colors? 12) How is spherical mirror used to converge a beam of sunlight? Name the type of mirror used. 13) A lens forms a virtual and enlarged image of a body. Can you say what type of lens is used? 14) A boy is observing his image in a plane mirror. The distance between the mirror and his image is 6 m. If he moves 2 m away from the mirror, what will be the distance between the boy and his image? 15) List down the differences between a real image and a virtual image. 16) As the angle of incidence is increased for a ray incident on a reflecting surface, the angle between the incident and reflected rays ultimately approaches what value? (a) 0° (b) 45° (c) 90° (d) 180° 17) If two plane mirrors are perpendicular to each other and θ1 = 40°, then find the value of θ2.

a) b) c) d)

40° 50° 30° 90°

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VII CBSE Physics – Light 18) A candle (height=20 cm) is kept 5 cm away from a plane mirror. What would the height of the image be? (a) < 20 cm (b) > 20 cm (c) = 20 cm (d) Can‘t be said 19) Why can‘t we see in dark? (a) Because eyes don‘t work in dark. (b) Because there is no light to reflect from the objects. (c) Both a and b (d) Power of eye is reduced. 20) If a ray of light is incident at an angle of 60° to the normal, then the angle formed by the reflected ray with the normal is equal to? (a) 30° (b) 90° (c) 60° (d) 180°

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VII CBSE Biology – Weather, climate and adaptation Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction: Weather vs. Climate Question 1. Sita - ―it rains a lot during spring in my village.‖ Gita - ― it is very hot and sunny today.‖ Who is talking about weather and who is talking about climate? Justify.

Let us study about weather and climate in detail.

2. Weather It is something that we experience on a daily basis. It is determined by the temperature, humidity, rainfall, wind speed, cloudiness, visibility, etc. Sun drives the changes in weather. Weather helps us to decide what we should wear for the day or what to bring on an upcoming getaway in the next week. Weather is a prediction based upon a variety of data collected in a variety of ways from ground stations to radars and weather maps are created to help us understand what to expect based on the evidence compiled by meteorologists.

Question 2. Earth is not the only planet that exhibits weather conditions. What is required for a planet to support weather systems?

Atmospheric pressure is the force of ____________ pressing down towards the surface. It varies with location. The difference in air pressure causes wind to move and in severe cases result in cyclones. The amount of moisture in air is called_____________________. Moisture present in air condenses to form clouds and its precipitation results in rain.

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Question 3. Why do weather forecasters use clouds to help predict the weather?

Question 4. Calculate the average maximum temperature and maximum humidity of a given place from the table given below.

Date 23-10-14 24-10-14 25-10-14 26-10-14

Max. Temp. (◦C) 35 40 42 39

Min. Temp. (◦C) 15 14 10 18

Max. Humidity (%) 45 48 40 42

Min. Humidity (%) 30 32 35 37

3. Climate It allows us to see long term patterns in weather data collected over time. Climate can tell us many things from seasonal information and planting zones to increases in global temperatures or carbon dioxide. The factors which determine climate are temperature, precipitation, altitude, latitude, geography, topography.

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VII CBSE Biology – Weather, climate and adaptation Question 5. Fill the table with appropriate words. Factor

Condition

Altitude

High altitude

Latitude

Near poles

Geography

Places bodies

Topography

High mountain areas

near

Temperature more

large

water

The Earth is divided into three zones based on average temperature. They are - Tropical, Temperate and Polar zones.

Question 6. Label the given diagram representing the different zones of the Earth.

Tropic Zone Tropic Zone

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4. Animal Adaptation Climate of a place has an effect on the organisms living there. Animals adapt to the climate of the place they live in order to survive.

Question 7. Define adaptation.

Let us study about the adaptations of different animals living in some specific regions on earth. a. Polar regions Polar Regions are the areas that surround the earth‘s geographic north and south poles. The area surrounding the North Pole is called the Arctic region while the area surrounding the South Pole is called the Antarctic region. These regions are very cold and are covered with snow for most part of the year. Let us look at the adaptations in some of the animals living in these regions. (i)

Polar bears

Figure 1: Polar bear



 

They have white fur which protects them from predators and helps them catch their prey by making them less visible in the snowy white background. They have two thick layers of fur and a layer of fat under their skin in order to keep them warm. They have wide and large paws which help them in swimming and walking in snow.

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Question 8. If a polar bear was adapted to live in a desert, would it still have thick fur? What would be its colour in order to camouflage?

(ii)

Penguins

Figure 2: Penguin

  

They are white which makes them less visible in the snowy white background. They have thick skin and fat under their skin to keep them warm in the cold climate. They have streamlined body and webbed feet which make them good swimmers.

Other animals in these regions are fishes, musk oxen, reindeers, foxes, seals, whales and birds. Birds migrate to ____________ areas during winters and come back when winter is over. b. Tropical rainforests These areas are generally hot because of their location near the equator and receive plenty of rainfall. Days and nights are almost equal in length throughout the year. They are found in Western Ghats and Assam in India, Southeast Asia, Central America and Central Africa. Some of the animals living in these regions and their adaptations are as follows:

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Did you know? Tropical rainforests are known as the lungs of the planet for the role they play in absorbing carbon dioxide and producing oxygen. Rainforests act as huge carbon sinks, taking in a major portion of carbon dioxide, a greenhouse gas and storing it in their roots, stems, leaves and branches.

Question9. Which of the following beaks allows birds to drink nectar from deep within flowers?

(A)

(B)

(i)

(C)

(D)

Red-eyed frog

Figure 3: Red-eyed frog



They have sticky pads on their foot which helps them to climb trees.

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Question 10. How do the red eyes of the red-eyed frog help in protecting it from its predators?

(ii)

Monkey

Figure 4: Monkey



They have long tail for maintaining balance and grasping branches. Their hands and feet are adapted to easily hold on to the branches.

Question11. How can you differentiate an ape from a monkey?

(iii)

Birds

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Question 12. Identify the organism in the picture and write about the various adaptive features which help in its survival.

(iv)

Big cats

Figure 5: Lion

 

They have thick skin and sensitive hearing capacity. Their body colour helps them to camouflage with the dry grass.

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Biology – Weather, climate and adaptation Lion-tailed macaque

Figure 6: Lion-tailed macaque

  

(vi)

It has silver white mane around its head. It is a good climber and spends a majority of its life on trees. It feeds mainly on fruits. It also eats seeds, young leaves, stems, flowers and buds.

Elephants

Figure 7: Elephant

  

It uses its trunk as nose and has a strong sense of smell. The trunk is also used for picking up objects. Its long tusks are modified teeth and help in tearing the bark of trees. Its large ears help in listening very soft distinct sounds.

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Question 13. Are the tusks the only teeth that elephants have? If no, explain.

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VII CBSE Biology – Weather, climate and adaptation Instructions: Solve these problems after watching the videos. 1. Fill in the blanks with appropriate words. Animal Habitat (i) Red Eyed Frog _____________ (ii) Beard ape _____________ (iii) Penguins _____________ 2. In Polar Regions, the Sun does not set for ____________ months. a. 2 b. 4 c. 6 d. 9 3. Tropical regions generally have ____________ temperature and are located near the ___________. a. Low, polar region b. Hot, equator c. Low, south pole d. Low, north pole 4. __________________ does not guide the birds while migrating. a. Sense of direction b. Magnetic field of Earth c. Flight ability d. Sun and stars 5. Example of an animal that hibernates is a. Woodchuck b. Cockroach c. Cat d. All of these 6. What is camouflage? Give an example. 7. What will happen if forests disappear? 8. What is the main reason that some places on Earth are warmer than the others? 9. What kind of climate does north-east India have? 10. During summer season sometimes we feel very uneasy due to continuous sweating. What is the reason of this continuous sweating? 11. How are clouds formed? 12. What are climate zones? 13. What is the importance of air pressure? 14. Why do some birds migrate during day and some choose to migrate during night? 15. Why do tropical rainforests contain more species than any other ecosystem? 16. Why are coral reefs known as the rainforests of the sea? 17. Why do penguins have dark coloured feathers on the back surface of their body? 18. What is the need of hibernation? 19. List some advantages of wetlands. 20. Write the differences between weather and climate.

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VII CBSE Chemistry – Fibre to Fabric Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Clothing in India and all over the globe varies with the ethnicity, geography, climate and cultural traditions of the people in that region. Historically, the fibres man used were those that he could harvest from the nature: cotton, silk and wool, all of which had their limitations. To overcome these limitations, humans applied technology, techniques and knowledge in the processing and manufacturing of synthetic fibres. Question 1. What do you mean by the term monomers?

2. Natural and synthetic fibres Natural fibres can be defined as a substance produced by plants and animals that can be spun into filament, thread or rope and then woven into fabrics. Question 2. What are fibres?

Question 3. What are synthetic fibres?

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a. Natural Fibres Natural fibres can be classified as:   

Silk Jute Flax i.

Silk Almost all of the greatest break-through which humans have made, starting from the discovery of fire in early Stone Age to the discovery of sub-atomic particles in modern times, has all been the result of human curiosity. This curiosity led to a gradual learning curve of our environment and even silk was a product of this human curiosity. Learning what silk was and what were its uses eventually led to the extraction of silk from silkworms.

Figure 1: Silkworm Life Cycle

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Question 4. Where did silk originate from?

ii.

Jute Jute fibres are composed primarily of the plant materials: cellulose and lignin. These Jute fibres are 100% biodegradable and are thus environmental friendly.

iii.

Flax Flax fibre is extracted from the stems of the flax plants and was an important textile material before the discovery of wool and cotton.

b. Synthetic fibres Types of synthetic fibres:     i.

Rayon Nylon Polyester Acrylic Rayon

Rayon is a nature-based material manufactured from the cellulose of wood pulp. The natural base gives it many advantages like: low cost, diversity and availability that led to its popularity and success. Question 5. Name the scientist who discovered rayon?

Question 6. Write the uses of rayon.

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Did you know? Flax is the earliest known natural textile fabric seen used in about 5000 BC. Flax is the material used to make linen which is seeing a huge come back today in drapery and upholstery.

ii.

Nylon Nylon is another synthetic fibre made without the use of natural raw material. It is prepared by using coal, water and air.

Question 7. Write the uses of nylon.

iii.

Polyester Polyester is a general term often defined as long chains of polymers chemically composed of at least 85% by weight of an ester, an alcohol and an acid Characteristics of polyester  

Polyester fabrics and fibres are extremely strong Polyester are wrinkle resistant even when washed and dried

Uses of polyester Polyester clothes were very popular due to its strength. It was also used to make ropes in industries. Today, PET bottles are one of the most popular uses of polyester iv.

Acrylic Acrylic fibres are synthetic fibres created from polymer of polyacrylonitrile. It is a combination of vinyl acetate and methyl acetate. The DuPont Corporation created the first acrylic fibres in 1941

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Question 8. What are the properties of acrylic fibre?

3. Plastic Plastic is a synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon, etc, that can be moulded into shapes while soft, and then set into rigid or slight elastic form. a. Thermosetting plastic Thermosetting plastics are materials which act as liquids or are generally malleable at low temperatures. These plastics are modified at low temperature to get the desired shape and then heated to high temperatures where they become irreversibly hard. b. Thermoplastic Plastic which gets deformed on heating and hard on cooling are called thermoplastics. PVC and polythene are examples of thermoplastic Question 9. Differentiate between Thermoplastic and Thermosetting plastic

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Question 10. Write the disadvantage of plastic

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Instructions: Solve these problems after watching the videos. 1. What are fibres? 2. Are your clothes made from natural or artificial fibres? 3. An expensive fabric which originated in China is ________. a. Wool b. Nylon c. Cotton d. Silk 4. Which of the below aren‘t natural fibres? a. Cotton and Jute b. Jute and Nylon c. Nylon and cotton d. Nylon and Rayon 5. Write a short note on rayon. 6. What are some uses of nylon? 7. What are PET bottles made up of? 8. Which kind of clothes shouldn‘t be worn in kitchens and laboratories? 9. Which fabric will you prefer if you are going for outdoor sports activities? 10. What was the need of artificial fibres? 11. What are some negatives of artificial fibres? 12. Example(s) of artificial fibres is(are): a. Rayon b. Nylon c. Polyester d. All of these 13. What are monomers and polymers? 14. What are artificial fibres mostly used in and why? 15. Is plastic a good conductor of electricity? 16. What are thermoplastics? 17. Define thermosetting plastics. 18. What are biodegradable and non-biodegradable substances? 19. Plastics are discouraged because of: a. Durability b. Poor conductivity c. Non-biodegradable nature d. Light-weight 20. What is the 4R principle?

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VII CBSE Biology – Respiration in Organisms Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Question 1. The world record for holding breath under water is 22 minutes and 22 seconds. How long you can hold your breath? Why can‘t you hold your breath for a long time?

Breathing is necessary because it provides oxygen for the various cellular reactions. Higher carbon dioxide levels trigger the urge to breathe. The process of acquiring oxygen and expelling carbon dioxide is known as respiration. The process of external respiration is also known as breathing. Both respiratory and circulatory systems are essential for respiration. The circulatory system is responsible for transporting oxygen and carbon dioxide to and from cells.

2. Respiration All organisms need energy to do work. Glucose is broken down in cells using oxygen to release energy that can be used for cellular processes. As the name says this process takes place inside the cell. In presence of oxygen Glucose ------------------------------------->Carbon dioxide + Water + Energy Question 2. List out the differences between respiration and combustion.

3. Aerobic vs Anaerobic Respiration As the name suggests aerobic respiration requires air, more precisely oxygen and anaerobic respiration takes place in absence of air (oxygen).

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Question 3. List out the differences between aerobic and anaerobic respiration.

Question 4. Name the type of respiration that takes place during sprinting and during endurance running.

4. Breathing Vs Respiration



Misconception: Breathing and respiration are often considered the same.

 Clarification: Respiration is the release of energy from the breakdown of glucose. Respiration takes place in every living cell and all cells need to respire to produce energy. Breathing is the process of getting oxygen into the lungs and carbon dioxide out of the lungs. It allows gas exchange to take place so that oxygen can be absorbed from the lungs into the blood and carbon dioxide is removed from the blood and breathed out from the lungs.

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5. How do we Breathe? So far we have discussed that we breathe in oxygen and breathe out carbon dioxide. Now, let‘s try to understand this mechanism of it. a. Components of Respiratory System Question 5. Label the parts in the following diagram.

Figure 1: Respiratory System in Humans

(i)

Nose and Nasal Cavity: The nose and nasal cavity constitute the main external opening of the respiratory system. They represent entry to the respiratory tract – a passage in the body through which air travels in order to reach the lungs. Although the nose is typically credited as being the main external breathing apparatus, its role is actually to provide support and protection to the nasal cavity.

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Question 6. What is the significance of the presence of mucus and hair in nasal cavity?

(ii)

Pharynx The pharynx is the next component of the respiratory tract, even though most people refer it simply as the throat, it resembles a funnel made out of muscles that acts as an intermediary between nasal cavity, larynx and the esophagus.

(iii)

Larynx The larynx is the next component, but represents only a small section of the respiratory tract that connects the pharynx to the trachea. It is commonly referred to as the voice box, and is located near the anterior section of the neck.

(iv)

Trachea The trachea is a longer section of the respiratory tract, shaped like a tube and approximately 5 inches in length. It has several C-shaped cartilage rings which are lined with tracheal epithelium.

Question 7 .What is the importance of rings of cartilage in trachea? Why it is C- shaped?

(v)

Bronchi The lower end of the trachea splits the respiratory tract into two branches that are named as primary bronchi. These first run into each of the lungs before further branching off into smaller bronchi. These secondary bronchi continue carrying the air

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(vi)

Biology – Respiration in Organisms to the lobes of the lungs, and then further split into tertiary bronchi. The tertiary bronchi then split into even smaller sections called bronchioles that spread throughout the lungs. Lungs The lungs are the primary organs of respiration in humans and in most other air breathing vertebrates.

Question 8. List the importance of presence of lungs in our body.

b. Stages of Respiration The process of respiration can be divided into three stages- External respiration, Internal respiration and Cellular respiration. External respiration involves breathing and gaseous exchange in lungs. Internal respiration involves the transport of oxygen from the lungs to different cells and the transportation of carbon dioxide from cells to the lungs. Cellular respiration refers to utilization of oxygen in breakdown of glucose to release energy. (i)

External respiration Breathing is the first step of respiration which includes inflow (inspiration) and outflow (expiration) of air between atmosphere and the lungs.

Question 9. Fill up the blanks to complete the path of air travelling in human respiratory system. Nasal cavity__________________ Larynx _________________ Bronchi  Primary Bronchioles_____________________________ Tertiary Bronchioles _________________

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Did you know? The lungs are the only organs that can float on water. Medical examiners use the so-called "lung float test" during autopsies to determine if a baby was stillborn (died in the womb). If the lungs float, the baby was born alive; if the lungs don't float, the baby was stillborn.

Alveoli The main site for gaseous exchange in lungs is the alveoli. Alveoli are made up of single celled epithelium and are supplied with blood capillaries which are also made up of single celled epithelium

Question 10. How do alveoli help in exchange of gases?

(ii)

Mechanism of Breathing The process of breathing involves the combined action of ribs, lungs, intercostal muscles and diaphragm. It involves two stages - inhalation and exhalation. It utilizes the principle of the movement of air from high pressure to low pressure.

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Figure 2: Movement of intercostal muscles and diaphragm during inhalation and exhalation

Question 11. Write the events that takes place during inhalation and exhalation.

(iii)

Internal Respiration Exchange of gases takes place by the movement of gaseous molecules from a region of its higher concentration to a region of its lower concentration by the process of ___________________. Movement of gases from lungs into the blood stream is the process of internal respiration. A higher concentration of oxygen in lungs enables hemoglobin in RBCs to bind to the oxygen to be transported. At the cell‘s site, higher concentration of oxygen in blood causes it to diffuse into cells. Similarly, a high concentration of carbon dioxide in cells causes it to diffuse into the blood. Most of the carbon dioxide is transported as bicarbonates in blood plasma. A small portion (~20%) can bind directly to hemoglobin.

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Figure 3: Gaseous exchange inside the body

(iv)

Cellular Respiration As the name suggests cellular respiration takes place in all living cells to generate energy for cellular functions. C6H12O6 +________ ------------------------------>_________ + H2O + ATP The above equation represents cellular respiration and its main goal is to release energy in the form of ATP. ATP is a high energy molecule with three phosphate groups. Three phosphates together are highly unstable. Breaking of these bonds provides us with the desired energy. In this process ATP is converted to ADP.

6. Breathing in Other Organisms Nature exhibits great diversity with respect to the way in which exchange of gases take place in different organisms.

Question 13. Match the following: (a) Bacterium (b) Earthworm (c) Insect (d) Amphibians (e) Fishes

(i) Skin (ii) Spiracles (iii) Cell membrane (iv) Gills (v) Lungs and skin

a. Insects Insects do not have a well-developed respiratory system as ours instead they have small holes present on the sides of their body called spiracles. The air rich in oxygen enters into the body of insects through these holes followed by fine tube like structures called trachea. Gaseous exchange takes place between the cells of the body and tracheal tubes.

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Figure 4: Diagram showing single spiracle and trachea associated with it

Question 14. Identify the position of trachea and spiracle in the given figure.

Figure 5: Respiratory System of Cockroach

b. Earthworm In earthworms respiration process takes place through its moist, thin and highly vascular skin. The oxygen gas absorbed by the skin diffuses into the body fluid and is transported to all the cells of the body. c. Fish Lungs cannot be used underwater. In order to extract oxygen from water fishes have a pair of gills present in either side of the head.

Figure 6: Respiratory System in Fishes

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Question 15. Explain the processes of gaseous exchange in fishes.

7. Gaseous exchange in plants Process involved in gaseous exchange in plants is diffusion. Direction of diffusion depends on two things viz. Environmental conditions and requirement of the plant. In day time, carbon dioxide given out during respiration by most animals is used for photosynthesis. Therefore, only oxygen is released; which is a major activity during the day. During night time only respiration takes place. Therefore only carbon dioxide is released. The gaseous exchange occurs through the stomatal pores.

Question16. Stomata is absent in roots and stems of woody plants. How does gaseous exchange take place in these parts of a plant?

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Instructions: Solve these problems after watching the videos. 1. The process of breakdown of food in the cell with the release of energy is called ________. a. Respiration b. Inhalation c. Exhalation d. Breathing 2. In man, which of the following structures is analogous to gills in fishes? a. Lungs b. Alveoli c. Nostrils d. Bronchioles 3. During heavy exercise, we get cramps in the legs due to the accumulation of a. Carbon dioxide b. Alcohol c. Lactic acid d. Water 4. During exhalation, the ribs a. Trachea b. Lungs c. Alveoli d. Nose 5. Exchange of gases takes place in a. Trachea b. Lungs c. Alveoli d. Nose 6. Name the muscular structure which forms the floor of the chest cavity. 7. Why should we not talk while eating? 8. How does exchange of gases take place in earthworm? 9. Why can you not hold your breath for a long time? 10. Anaerobic respiration produces more energy than aerobic respiration. (True/False) 11. What is the difference between breathing and respiration? 12. Why are the respiratory organs different in different organisms? 13. Why is it said that we should not sleep under trees at night? 14. Do we breathe out only carbon dioxide during exhalation and breathe in only oxygen during inhalation? 15. The air that we breathe in contains a lot of nitrogen. What happens to that nitrogen in our body? 16. What are the respiratory organs in aquatic mammals? 17. What is the difference between bronchi and bronchioles? 18. How does hot water bath and massage help in case of body ache? 19. Why is it told to cover your nose and mouth while sneezing? 20. Why is respiration an essential life process?

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VII CBSE Biology – Reproduction in Organisms Instruction: This booklet can be used while watching videos. Keep filling the sheet as the videos proceed.

1. Introduction Reproduction is the process in which new organisms are produced from their parents. It is essential for the survival of species. All living things ensure that they pass down their genes through reproduction.

Question 1. How is sexual reproduction advantageous over asexual reproduction?

2. Fission It is a type of asexual reproduction in which reproduction occurs by splitting the body into parts. Fission is of two types- Binary and Multiple. Binary fission results in formation of ______________cells from a single parent while multiple fission results in formation of ________________ cells. Fission requires replication and division of genetic material. Most bacteria and protozoa divide along a specific plane during division. For amoeba, this can occur along any plane. Multiple fission usually occurs during ______________________ conditions producing many daughter cells within a protective covering called cyst. When conditions become more_________________, the cyst breaks and daughter cells are liberated.

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VII CBSE Biology – Reproduction in Organisms Question 2. Identify whether binary fission occurs on a single plane or along any plane in the organisms shown below?

3. Fragmentation Fragmentation occurs in colonial organisms or simple multi-cellular organisms. Organism split into fragments and each fragment develops into new organism which is a clone of the parent. Splitting may be intentional or accidental. Examples of organisms that can undergo fragmentation are ________________________________________________.

Parent Spirogyra

Daughter Spirogyra

Figure 17: Fragmentation in Spirogyra

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VII CBSE Biology – Reproduction in Organisms Regeneration is the process in which a part of an organism can completely generate an entire individual or some parts of its body. Regeneration is used as a mode of reproduction only by simple organisms with less complexity of organization. Starfish, lizards, planaria and hydra all exhibit some form of regeneration. More complex organisms only have limited regeneration capacity. Question 3. How is regeneration different from fragmentation?

When organisms are born they start with a single cell. This cell can grow into any cell in the body. Such cells are called________________________. The process in which stem cells become specialized cells is called ___________________________ .

4. Budding Budding generally results in offspring that is smaller than its parent. Budding is possible in both unicellular and multi-cellular organisms. A new offspring results when a bud breaks away from its parent.

Parent hydra

Hydra with bud

Bud grows into a new hydra

Figure 18: Budding in Hydra

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New hydra detaches

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VII CBSE Biology – Reproduction in Organisms Question 4. Differentiate between budding and binary fission.

Question 5. Draw a neat labeled diagram to show budding in yeast.

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Biology – Reproduction in Organisms

5. Spore Formation Spore formation occurs in simple multicellular organisms. In algae, the protoplast divides to form small motile spores known as ___________________. These spores when released in the surrounding develop into new individuals. The process is same in case of bread moulds. Thread –like structures appear on the surface of the bread when it is moist. These structures are called___________. At the end of these structures, sporangia are present which contain ____________ that can develop into new rhizopus.

Figure 19: Spore Formation in Rhizopus

Question 6. Why are spores covered in a protective layer?

6. Vegetative Propagation Vegetative propagation is a type of ______________________ reproduction in plants in which a new plant can develop from vegetative parts of parent. It can be natural or artificial. a. Natural Methods This occurs naturally in which new plant comes from roots, stems or leaves of the existing plant for example buds on root of sweet potato grow into new plants. Stems can also bear buds such as in grasses. Leaves and tubers also bear buds in many plants.

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A. Potato

B. Bryophyllum

C. Ginger

Figure 20: Growth of new plant from a bud

Question 7. Which part of a spider-plant bears buds?

Did you know? During the 1600s, tulips were so valuable in Holland that their bulbs were worth more than gold. The craze was called tulip mania, or tulipomania, and caused the crash of the Dutch economy. Tulips can continue to grow as much as an inch per day after being cut.

b. Artificial methods (i)

Grafting Grafting involves taking two plants of different breeds and producing superior quality plant. The plant whose root system is taken is called _____________________ and the plant whose shoot system is taken is called ________________________.

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Figure 21: Method of Grafting

Question 8. Is it possible to graft different species of plants together? If yes, what should be the characteristics of the two species? If no, why not?

(ii)

Stem cutting Stems with nodes and internodes are planted in soil which grow roots and become fully fledged individuals.

Figure 22: Stem cutting in rose

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Question 9. Apples, pears, avocados, oranges and roses are commonly grown by stem cutting. Why this method is is preferable as compared to using seeds obtained by sexual reproduction?

(iii) Layering In layering a stem is buried in the soil while it is still attached to the parent plant. Roots develop in the buried stem and can grow into individual plants. E.g. ______________. In air layering the bark from a small part of stem is removed, covered with soil and wrapped with a cloth. Water is sprinkled on this part regularly. When the stem develops root it is cut from the parent plant and planted as a new plant.

Figure 23: Method of Air Layering

(iii)

Tissue Culture A small tissue, generally from a bud or growing area, is cut from a plant and kept in a dish containing aseptic growing medium. The tissue soon develops a mass of cells known as a callus. The callus is then placed in a medium that causes it to differentiate and produce baby plants. Orchids, chrysanthemum, asparagus, carnations, etc. are usually grown by this method.

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Question 10. What are the advantages of tissue culture? How is it better than stem cutting?

7. Sexual Reproduction in Plants The flower is a reproductive organ of plant. Most plants have both male and female reproductive organs in the same flower. Others may produce different male and female flowers.

a. Structure of Flower Question 11. Label the different parts of the flower.

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VII CBSE Biology – Reproduction in Organisms The male part of the flower is __________________________________. The female part of the flower is _________________________. The male gametes of the plant are known as ______________________ and are contained within the _______________________. The stigma receives pollen grains in a process known as _____________________. The style bears the stigma and the ovary. Ovary contains ovules. Ovules are structures where embryo sacs develop and mature into seed. Did you know? Saffron is used as a flavoring agent in cooking. It is harvested from the stigmas of a type of fall-blooming crocus, Crocus sativus.

b. Pollination The transfer of pollens from anther to stigma of flowers is called pollination. Pollination can be self-pollination or cross pollination. Question 12. Identify the type of pollination in each case.

A

B

c. Fertilization The pollen grain grows a pollen tube in the stigma and style releasing the male gametes. The tip of the pollen tube ruptures in the ovule to release two male gametes. One of the male gametes fertilizes the egg cell in the ovule to form a zygote. The second gamete fuses with the secondary nucleus to form the endosperm nucleus. The zygote forms a

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Biology – Reproduction in Organisms ________________. The endosperm nucleus becomes the endosperm of seed. The ovule forms the _______________.

Figure 24: Growth of pollen tube



Misconception: In the life cycle of a flowering plant, the fruit develops before the seeds.



Clarification: Upon union of the female gamete (in the ovule) with the male gamete (from the pollen), the seed is formed, and only after that, the fruit develops from the ovary. In other words, the fruit is developed only after the process of fertilization which results in the seed formation, as a by-product of the reproductive process. The fruit develops to protect the seeds, and in some cases, develop to become "attractive" to animals that will be the agents of seed dispersal.

Question 13. Some plants like apple and pear have flowers that do not develop into seeds unless cross fertilized. What advantages does such a mechanism provide? Can it be a disadvantage?

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8. Dispersal of Seeds Seed dispersal is the movement or transport of seeds away from the parent plant. Plants have very limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors. Question 14. Seeds bear the future plants within them. These future plants are children of the parent plant. Dispersal of seeds is nature‘s injustice to the plant as their children are separated from them. Do you agree with this statement? Why or Why not?

Question 15. Match the following. Seeds i. ii. iii. iv.

Drumstick and maple Madar and sunflower Xanthium Pea

Coconut

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Dispersed by

a. water b. wind c. Animal d. burst with sudden jerk

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Instructions: Solve these problems after watching the videos. 1. Which of the following is not a stage in sexual reproduction? a. Photosynthesis b. Pollination c. Fertilization d. Germination 2. Choose the correct order of occurrence of the following processes. a. Pollination, seed formation, fertilization, germination, seed dispersal b. Germination, pollination, seed dispersal, fertilization, seed formation c. Fertilization, pollination, germination, seed dispersal, seed formation d. Pollination, fertilization, seed formation, dispersal, germination 3. Pollination is a. Transfer of female gametes from stigma to anther b. Transfer of male gametes from stigma to anther c. Transfer of male gametes from anther to stigma d. Transfer of female gametes from stigma to anther 4. Choose the correct statement. a. Stamen is the male part of the flower b. Stamen is the female part of the flower c. Carpel is the male part of the flower d. Corolla is the male part of the flower 5. In grafting, the root cutting is called stock while the stem cutting is called a. Transplant b. Bud graft c. Scion d. Shoot stock 6. What is the difference between cutting and grafting? 7. Write about the different ways in which seeds can be dispersed. 8. What is common among earthworm, leech and sponge? 9. How is reproduction in hydra different from that in humans? 10. Differentiate between budding and binary fission. 11. Explain binary fission in amoeba with the help of a diagram. 12. In which plant buds are present on the margins of leaves? 13. How is regeneration different from fragmentation? Explain with the help of examples. 14. How can stem cells be used in the field of medicine? 15. Why is asexual reproduction in plants called vegetative propagation? 16. What are buds? 17. Why do we use artificial methods of vegetative propagation? 18. What is differentiation? 19. Why do some fruits have only one seed while some have more? 20. What is the fate of the floral parts after fertilization?

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