Form 2 Chapter 5

Form 2 Science Chapter 5

FORM 2 CHAPTER 5 WATER AND SOLUTION

1. Diagram 1 shows the apparatus used in the electrolysis of water. Test tube P

Test tube Q

Water + Substance Z Carbon rod Y

Carbon rod X

Diagram 1

(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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(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]

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Form 2 Science Chapter 5

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

Diagram 2 (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:

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(ii) boils: …………………………………………………………………………………………… [2 marks] (f) What happens to the motion of water molecules when water (i) freezes: ………………………………………………………………………………………… (ii) boils:………….………………………………………………………………………………… [2 marks]

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

Diagram 3 (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? ………………………………………………………………………………………………………

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……………………………………………………………………………………………………… [2 marks]

(f) State two other factors that influence the rate of evaporation. (i) ……………………………………………………………………………………………….... (ii) ………………………………………………………………………………………………….. [2 marks]

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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 Q

P

Milk of magnesia

Orange

R

S

Toothpaste

Vinegar Diagram 4.1

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: …………………………………………………………………………..……………………. JPN Pahang 2009

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[4 marks]

(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 P, Q, R, and S

Common property

Names of substances

[4 marks]

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

Dilute hydrochloric acid

Sodium hydroxide solution + universal indicator Diagram 5.1 The results of the activity are recorded in Table 5.2 Change in colour of universal indicator pH value

Initial Purple 9

Final M 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. Hydrochloric acid

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Sodium hydroxide

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[2 marks]

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

0

1

2

lemon

3

4

5

apple

6

7

8

tomato

10

9

11

toothpaste

12

13

14

soap

Milk of magnesia

Diagram 5.2

(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]

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