IGCSE Chemistry States of matter topical questions

Name the change of state for each description.

1. (a)A solid turning into a liquid[1]
2. (b)A gas turning into a liquid[1]
3. (c)A liquid turning into a solid[1]

A student says that a gas can be squeezed into a smaller volume but a liquid cannot. Explain this difference using particles.

Three samples of the same substance are described. Sample A: particles vibrating about fixed positions in a regular pattern. Sample B: particles close together but able to slide past one another. Sample C: particles far apart and moving quickly in all directions.

1. (a)Identify which sample is a liquid.[1]
2. (b)Describe the arrangement of the particles in a solid.[1]
3. (c)Name the change of state when sample B is cooled until it behaves like sample A.[1]

A gas diffuses across a room and is smelt in a kitchen.

1. (a)Name the process by which the gas spreads.[1]
2. (b)Explain, in terms of particles, how the gas spreads.[2]
3. (c)State and explain one change that would make the gas spread more quickly.[2]

A fixed mass of gas is trapped in a syringe at constant temperature. The volume is halved from 200 cm³ to 100 cm³.

1. (a)State what happens to the pressure of the gas.[1]
2. (b)Explain your answer in terms of particles and collisions.[2]

Solid X is a white solid that melts at 65 °C. A student warms a sample of X steadily and records the temperature every 30 seconds.

1. (a)Describe how the recorded temperature changes while the solid is melting.[1]
2. (b)Explain why the temperature behaves in this way.[2]
3. (c)State what happens to the arrangement of the particles as X melts.[1]

A drop of a volatile liquid is placed on the back of a student’s hand. The drop slowly disappears and the skin underneath feels cold.

1. (a)Name the process by which the drop disappears.[1]
2. (b)Explain, in terms of particles, why the skin feels cold.[2]
3. (c)State one change that would make the drop disappear faster.[1]

Two gas jars are connected by a tube. Ammonia (Mᵣ = 17) is at one end and hydrogen chloride (Mᵣ = 36.5) at the other. A white ring of ammonium chloride forms where the two gases meet.

1. (a)Predict which end the white ring forms nearer to, and explain your answer.[3]
2. (b)State one assumption you make.[1]

An impure solid is heated from room temperature to well above its melting point. Its temperature is measured every minute.

1. (a)Sketch or describe the shape of the temperature–time graph for the impure solid.[2]
2. (b)Explain how the graph shows the sample is impure.[2]

A deep-sea diver exhales an air bubble with a volume of 2.0 cm³ at a depth where the pressure is 500 kPa. The bubble rises to the surface, where the pressure is 100 kPa. The temperature of the trapped air stays constant.

1. (a)Calculate the volume of the bubble at the surface.[2]
2. (b)Explain, in terms of particles, why the volume changes in this way.[2]
3. (c)State the assumption you make in this calculation.[1]