Ans Science Obc

ANSWERS

SCIENCE Science marking scheme Paper 2 SECTION A Answers 1.

(a) Use the results from table to draw a graph of force against extension.

Force (N)

10 8 6

Straight line -1 All correct points -1

4 2

1

2

3

4

5

6

Extension (cm)

(b) The spring extension increases when the forces increase // the bigger the load force is, the longer spring extension (c) In the experiment, state the (i) Fixed variable : Type of spring

2. (a)

(ii)

Manipulated variable : Forced applied // weight of load

(iii)

Responding variable : Extension of spring

i) Bacteria grow better in the dark ii) Bacteria need moisture to grow (humidity) iii) Bacteria need nutrients to grow

ANSWERS Science marking scheme Paper 2 SECTION A Answers 1.

(a) Use the results from table to draw a graph of force against extension.

Force (N)

10 8 6

Straight line -1 All correct points -1

4 2

1

2

3

4

5

6

Extension (cm)

(b) The spring extension increases when the forces increase // the bigger the load force is, the longer spring extension (c) In the experiment, state the (i) Fixed variable : Type of spring

2. (a)

(ii)

Manipulated variable : Forced applied // weight of load

(iii)

Responding variable : Extension of spring

i) Bacteria grow better in the dark ii) Bacteria need moisture to grow (humidity) iii) Bacteria need nutrients to grow

ANSWERS (b) pH of the culture

3. (a) producer/any plant eg. grass

(b) frog (c) i) grasshopper ii) secondary consumer (d) The population of frogs would increase. (e) sparrow hawk/eagle 4. (a) Purification (b) microorganisms (c) (i) palm oil/crude oil (ii) vitamin A/E (d) mesocarp

ANSWERS SECTION B Answers 5. Figure 6 shows an impulse pathway when a student accidentally touches a sharp needle Relay neurone/interneuron Sensory neurone

receptor

Synapse

Motor neurone

(a) contract (b) (i) Reflex action (ii) Spinal Cord 6. (a) (i) Green Plants (ii) Light Energy (b) When animals eat organism P. (c) (i) Respiration (ii) Respiration supplies energy to living organisms (d) Decomposition an combustion

muscle

ANSWERS

7. (a) image (b) (i) The size of the image is smaller than the size of the object. (ii) Real, inverted and diminished (c) (i) Virtual, upright and larger (ii) Real, inverted and diminished (d) projector 8. (a) transistor (b) (as drawn in figure) (c) inductor (d) detector circuit (f) electrical energy is changed to sound energy 9. (a) Natural rubber treated with sulphur monochloride solution is more elastic than the untreated one. (b) Vulcanisation (c) (i) type of clip and the weight (ii) type of rubber (d) stronger/more elastic/more heat resistant

ANSWERS SECTION C Answers 10.

a) Bacteria need suitable or optimum temperature to reproduce and grow rapidly. b)

i) Aim of experiment: To observe the effect of temperature on the reproduction and growth of bacteria. ii) Variable Kept constant: Sterilised nutrient broth, types of bacteria, incubation period Manipulated : Temperature Responding : Growth and reproduction of bacteria. iii) List of apparatus/material Three sterilized test tubes, syringes, marker pen, strilised nutrient broth, bacteria, cotton. iv) Procedure 1. The apparatus as shown in the above diagram is set 2. The test tubes are labeled A,B and C. 3. All the three test tubes are kept in incubators at different temperatures as shown in the diagram. 4. The test tubes are observed after two days.

Test Tube A (Very cold 10º C) B (Medium 30ºC) C (Hot 70ºC)

Results

vi) Conclusion Bacteria can only grow and reproduce rapidly at suitable temperature.

ANSWERS 11. a) Body size : A person with big body size requires more calories than a person with a small body size because they have more cells to metabolise. Age: Young people like teenagers require more calories than old people because they are more active . Sex : Males require more calories than females because generally males are more active than females. Surrounding temperature : People living in a cold place require more calories than people living in hot climate because they need to burn more calories to maintain their body temperature. b) i) Unhealthy eating habits / eating too much ii) - Consuming too much high calorie food such as fats and sugar will cause obesity. - Fats contain a high level of cholesterol which leads to narrowing of the arteries ( arteriosclerosis) - Excessive intake of sugar will cause diabetes - When fats start to accumulate it will cover organs such as the heart, making it weak and ove-burdened. iii) Reduce intake of calories iv) - Reduce consumption of fatty food, sweet food, and eat moderately - Exercise regularly