Form 2 Science Chapter 5

FORM 2 CHAPTER 5 WATER AND SOLUTION

1. Diagram 1 shows the apparatus used in the electrolysis of water.

(a) Suggest one example of substance Z.

…………………………………………………………………………………………………….

[1 mark]

(b) Which of the two carbon rods function as the negative electrode?

………………………………………………………………………………………………………

[1 mark]

(c) When the circuit is switched on, some gas is collected in each test tube.

(i) What is the gas collected in test tube P?

…………………………………………………………………………………………………..

[1 mark]

(ii) Suggest one way to identify the gas collected in test tube P.

…………………………………………………………………………………………………

[1 mark]

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Test tube P

Water + Substance Z

Diagram 1

Test tube Q

Carbon rod X Carbon rod Y

Form 2 Science Chapter 5

(iii) What is the gas collected in test tube Q?

……………………………………………………………………………………………….

[1 mark]

(iv) Suggest a way to identify the gas collected in test tube Q .

………………………………………………………………………………………………

[1 mark]

(d) State the expected ratio of the volume of the gas collected in test tube Q to the volume of the gas collected in test tube P.

……………………. ………………………………………………………………………………..

[1 mark]

JPN Pahang 2009 88

Form 2 Science Chapter 5

2. Diagram 2 shows an activity conducted to determine the freezing point and the boiling point of water.

(a) Why is salt added to the ice cubes in A?

………………………………………………………………………………………………………

[1 mark]

(b) What is the function of the glass tube in B?

………………………………………………………………………………………………………

[1 mark]

(c) State the temperature of water in A when it begins to freeze.

………………………………………………………………………………………………………

[1 mark]

(d) State the temperature of water in B when it begins to boil.

………………………………………………………………………………………………………

[1 mark]

(e) What is the change in the state of matter when water

(i) freezes: …………………………………………………………………………………….

(ii) boils: ……………………………………………………………………………………………[2 marks]

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Diagram 2

Form 2 Science Chapter 5

(f) What happens to the motion of water molecules when water

(i) freezes: …………………………………………………………………………………………

(ii) boils:………….…………………………………………………………………………………

[2 marks]

JPN Pahang 2009 90

Form 2 Science Chapter 5

3. Diagram 3 shows an experiment to study the effect of humidity on evaporation.

(a) State the variables in the experiment.

(i) Manipulated variable: ………………………………………………………………………..

(ii) Responding variable: ……………………………………………………………………….

(iii) Constant variable: ……………………………………………………………………………

[3 marks]

(b) What is the function of the anhydrous calcium chloride?

………………………………………………………………………………………………………

[1 mark]

(c) Name another chemical substance that can be used to replace the anhydrous calcium chloride.

………………………….………………………………………………………………………….

[1 mark]

(d) Why is the beaker containing water placed in the bell jar P?

………………………………………………………………………………………………………

[1 mark] (e) What would be observed in bell jar P and bell jar Q after one hour? Why?

………………………………………………………………………………………………………

………………………………………………………………………………………………………

[2 marks]

JPN Pahang 2009 91

Diagram 3

Form 2 Science Chapter 5

(f) State two other factors that influence the rate of evaporation.

(i) ………………………………………………………………………………………………....

(ii) …………………………………………………………………………………………………..

[2 marks]

JPN Pahang 2009 92

Form 2 Science Chapter 5

4. Diagram 4.1 shows pictures of substances P, Q, R and S.Table 4.2 shows the pH of the substances P, Q, R and S when tested with universal indicator

Substance P Q R S

pH 9 3 8 2

Table 4.2

(a) Based on your observation on Diagram 4.1 and Table 4.2 state one property of substances P, Q, R and S .

P: …………………………………………………………………………………………………..

Q: …………………………………………………………………………………………………..

R: …………………………………………………………………………………………………..

S: …………………………………………………………………………..…………………….

[4 marks]

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Diagram 4.1

Milk of magnesia

P

Orange

Q

Toothpaste

R

Vinegar

S

Form 2 Science Chapter 5

(b) Classify the substances P, Q, R and S into two groups based on their common properties.

Write the names of the substances belonging to each group

[4 marks]

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Common property

P, Q, R, and S

Names of substances

Form 2 Science Chapter 5

5. Diagram 5.1 shows the reaction between dilute hydrochloric acid and sodium hydroxide.

The results of the activity are recorded in Table 5.2

Change in colour of universal indicator

Initial FinalPurple M

pH value 9 7

Table 5.2

(a)(i) State the colour of M.

…………………………………………………………………………………………………….

[1 mark]

(ii) Name the process that causes this change in colour. …………………………………………………………………………………………………….

[1 mark]

(iii) Complete the word equation that shows the reaction.

[2 marks]

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Dilute hydrochloric acid

Sodium hydroxide solution + universal indicator

Diagram 5.1

Hydrochloric acid + Sodium hydroxide +

Form 2 Science Chapter 5

(b) Diagram 5.2 shows several substances with different pH values.

(i) Based on Diagram 5.2, complete the table below by giving one example for each group of substances.

Acidic Alkaline

[2 marks]

(ii) What is the pH value of distilled water?

…………………………………………………………………………………………………….

[1 mark]

(iii) Why do we use toothpaste to brush our teeth? …………………………………………………………………………………………………….

[1 mark]

JPN Pahang 2009 96

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

lemon apple tomato toothpaste soap

Milk of magnesia

Diagram 5.2