Chemistry Matters for G.C.E. ‘O’ Level Chapter 1

Chapter 1 Kinetic Particle Theory

Answers to Textbook Exercises

Test Yourself 1.1 (page 2)

1. Solid, liquid and gas2. Liquid

Test Yourself 1.2 (page 6)

1. (a) Gas(b) Solid

(c) Arrangement in (a): Arrangement in (b):

2. (a) The particles in a liquid are closely packed. However, the particles are not held in fixed position. The particles cannot be compressed but they can slide over one another.

(b) Ice is a solid. The particles are closer together than in water vapour, giving it a higher density. In water vapour, the particles are much further away from each other, giving it a very low density. (1 g of ice has a volume of about 1.09 cm3, 1 g of water has a volume of 1.0 cm3 and 1 g of water vapour has a volume of about 1333 cm3.)

Test Yourself 1.3 (page 14)

1.

2. (a) Sublimation occurred. The mothball must be made of substance that sublimes.

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gas

solid

40 –

70 –

80 –

100 –

Temperature (°C)

Time (min)

liquid

solid and liquid

solid

0

Chemistry Matters for G.C.E. ‘O’ Level Chapter 1

(b) The volatile alcohol evaporated by absorbing heat from the skin.

3.Heat taken in Heat given outsublimation, evaporation, boiling, melting

condensation, freezing

Test Yourself 1.4 (page 19)

1. (a) (i) Nitrogen(ii) Chlorine

(b) (slowest) Chlorine < sulphur dioxide < carbon dioxide < nitrogen (fastest)

2. Removal of unpleasant smells; removal of polluting gases; spreading of smell of flowers and perfumes

3. (i) Experiment III(ii) Experiment IIncrease in temperature speeds up the rate of diffusion.

Exercise 1 (page 20)

Foundation

1. C 2. C 3. A 4. D

5. (a) (i) E(ii) C and D(iii) A and B

(b) As the temperature drops from 80 C, the gas particles lose kinetic energy and move more slowly. Eventually the movement of the particles is slow enough for the gas to change to a liquid at 58 C. On further cooling, the particles move slowly until the temperature reaches 7 C and the liquid becomes a solid. The particles now can only vibrate in fixed positions. As the temperature cools further to 10 C, the particles vibrate more slowly in their fixed positions.

6. The smell given out by perfumes is made up of tiny gas particles that move around freely. The particles diffuse from a region of higher concentration (the person) to a region of lower concentration (the other parts of the room).

Challenge

1. D

2. (a) 50 C(b) 26 C. The temperature shown in the graph does not drop below 26 C.(c) The particles gain kinetic energy and move more rapidly until they reach their

boiling point of 128 C. They now have sufficient energy to overcome the forces of attraction holding them together. The liquid X has changed to the gaseous state.

(d) AB, BC and CD

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Chemistry Matters for G.C.E. ‘O’ Level Chapter 1

(e)

3. (a) When solid ammonium chloride is heated, it turns into a gas (ammonia and hydrogen chloride). Thus, it disappears. On the colder part of the test tube, the solid ammonium chloride vapour is reformed without going through liquid state. Thus, it reforms in the cooler part of the test tube.

(b) Ammonia diffuses faster than hydrogen chloride gas. This is because the molecular mass of ammonia (i.e. 17) is less than the molecular mass of hydrogen chloride (i.e. 36.5). Hence, ammonia is detected first.

4. (a) Evaporates very readily at room temperature and pressure(b) As the ether evaporates, it absorbs heat, thus lowering the temperature. Ether

evaporates faster than water, so the temperature of the gauze moistened with ether is lower.

(c) Since ether catches fire very easily, keep the thermometers away from naked flames.

5. (a) Diffusion is the movement of particles from a region of higher concentration to a region of lower concentration.

(b) Chlorine. It has the highest molecular mass.(c) Any gas with molecular mass greater than 71, e.g. bromine.(d) It is very soluble in water(e) Ethene has the same molecular mass as carbon monoxide.

6. Experiment 1: When the tap was opened, the bromine particles will collide with particles of gases in bulb B and therefore diffuse more slowly to fill both bulbs.Experiment 2: There is no air and therefore no gas particles in bulb B. When the tap was opened, the particles of bromine can diffuse very rapidly to fill both bulbs due to less collision.

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128

Temperature (C)

Time (s)

50

30

0

solid

solid + liquid

liquid

liquid + gas

gas