Sce2 Marking Sbh

1511/2 SCIENCE SPM EXCEL 2 MARKING SCHEME SECTION A (20 marks) 1.

(a) Setiap titik betul

1 mark 1 mark

Garisan betul dan licin

2.

3.

(b) The temperature of the solution increases with time

1 mark

(c) 100 oC

1 mark

(d) 102 oC / 103 oC / 104 oC

1 mark

(a) 0.2

1 mark

(b) (i) State of copper (II) sulfat (ii) Type of substance

1 mark 1 mark

(c) Copper (II) sulphate conducts electricity in solution form.

1 mark

(d) Ionic compound is a substance which conducts electricity in solution form.

1 mark 1 mark

(a) The slide from the pollutant environment, contains more dust and particles than the slide from the cleanest environment. (b) Type of environment / areas of conducting the experiment.

1 mark

(c) Area A

1 mark

(d) (i) The slide contains more dust and particles.

1 mark

(ii)

1 mark

4.

(a) 3.1 cm. or 3.2 cm

1 mark

(b) Correct bar chart as shown.

2 mark

Length against strip Length / 6 5 cm 4 3 2 1 0 1

(c) (i) Acceleration (ii) 6 cm

2

3

4

5 Strip

1 mark 1 mark

SECTION B: 30 marks

5.

a.

6.

b. c. d. e. a.

7.

b. c. d. e. a. b. c.

8.

d. a. b.

9.

c. d. a. b. c. d.

Q : cerebrum R : cerebellum to increase surface area encase in the cranium // has cerebrospinal fluid in-voluntary action blind / lost vision P: meiosis Q: mitosis ovaries identical twins same gender/genetic composition Y-chromosome haber process i. iron ii. to speed up reaction // as a catalyst i. 450oC – 550oC ii. 200 atmosphere nitrogen + hydrogen Æ ammonia X : fermentation Y : esterification X : glucose Y : ester Colourless // tasteless // vapourized easily To make perfume // food flavouring P: thermoplastic Q: thermosetting plastic bakelite / epoxy / melamine i. Q / thermosetting ii. it has cross-link between the polymers recycling

1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m 1m

SECTION C [20 marks] Question 10. a. b. i. (ii)

(iii)

(iv)

Marking Scheme Hypothesis : A neutral pH value is most suitable for the growth of microorganisms. Aim of the experiment To identify the most suitable pH value for the growth of microorganisms. Identification of variables Constant variable : - Type of nutrient - Humidity/ Moisture - Light intensity - Surrounding temperature - Volume of drain liquid used/microorganism - Culture/ size of the culturing loops - Time for incubation

Mark 1

Manipulated variable : pH value of the medium

1

Responding variable : Number of microorganisms colonies

1 (Max:2)

List of apparatus and material: 1 cm³ of alkali solution (pH 10) 1 cm³ acid solution (pH 5) 1 cm³ of distilled water (pH 7) 3 Petri dishes of nutrient agar Drain liquid Beaker Culturing loop Procedure

1 1

1 4

1 cm³ of alkali / acid solution + nutrient agar + culture of microorganisms

Figure 1 : Microorganisms culturing with a different concentrations of alkali/acid

(v)

1. 1 cm³ of alkali is added into a Petri dish of nutrient agar. (pH 10) 2. The cover of the Petri dish is labelled according to the medium used. All materials and apparatus are sterilized. 3. Step 1-2 are repeated by using the 1 cm³ acid solution. (pH 5) 4. 1 cm³ of distilled water is added into the third Petri dish of nutrient agar and also labeled. (This is the neutral medium) 5. At the same time, the drain liquid is cultured into the 3 different labeled Petri dishes of steps 1-4. 6. Then, those Petri dishes are kept in room temperature (37ºC) for 24 hours in an inverted position. 7. After 24 hours, the number of microorganisms colonies is counted on every Petri dish. 8. The observation is recorded in a table. Tabulation of data pH of the medium 5 7 10

Number of microorganisms colonies

1

11. a.

Explain the effects of light when green plants absorb it. * * * *

Green plants absorb light to carry out photosynthesis which is a process to make food using carbon and water. Light energy which is absorbed by green plants is used to break up water molecules into hydrogen and oxygen. Then the hydrogen combines with carbon dioxide to form glucose while oxygen is released through the stomata into the air. The effects of light when green plants absorb it is shown in the following equation : .

1 1 1 1

Light Carbon dioxide + water

glucose + oxygen chlorophyll

b.

Identify the problem Heavy smoke pollution prevents green plants from absorbing light which is needed to carry out photosynthesis.

1

two methods to solve the problem Heavy smoke is usually produced by factories and vehicles. Solutions are shown below Pollution source Factories

Vehicles

Pollution control / Solution Do not build factories everywhere but at selected places only.

Explanation So that smoke will not prevent green plants in most places from absorbing light.

Use the best fuel, example petrol and make sure vehicles services are properly managed.

So that vehicles do not produce so much smoke.

Remark: 1 mark for method 1 mark for explanation

Maximum: 2 methods and 2 explanations Choose the best method and explain your choice. [Answer can also be any acceptable method and explanation] Building factories only at selected places. This is because we cannot avoid from having factories so at least green plants in most other places are still able to absorb light in order to carry out photosynthesis.

1

12 (a)

labeled diagram to show the radio transmission system.

2

microphone

Figure 3 : Radio transmission system

Explanation 1. The sound waves are changed into audio waves by the microphone. Then its amplitude is increased by the amplifier. 2. The oscillator generates radio frequency carrier waves and send them to the modulator where it is combined with the audio waves to produce modulated carrier waves that are transmitted to the aerial which will convert the modulated carrier waves into radio waves. b. i.

1 1

Identify two common characteristics of the waves. - Both can travel through vacuum - Both travel at the speed of light

1 1

ii

Other example : Satellite, Internet (or any acceptable answer) Non-example : CD player, telegraph (or any acceptable answer)

1 1

iii.

- Construct an initial concept on how these waves are useful for transmitting information - Radio wave is a type of electromagnetic wave that can be used in communication.

1

iv.

Explain the actual concept developed Radio waves are waves used in radio transmission that can travel through vacuum and at the speed of light

1