IGCSE Thermal Physics (0625)

Which statement about evaporation is correct?

• evaporation causes the temperature of the remaining liquid to decrease

• evaporation does not occur from a cold liquid near its freezing point

• evaporation does not occur from a dense liquid, such as mercury

• evaporation occurs from all parts of a liquid

Gas is stored in a sealed container of constant volume. The temperature of the gas increases. This causes the pressure of the gas to increase. What happens to the gas molecules during this pressure increase?

• The average kinetic energy of the molecules increases

• The average separation of the molecules decreases

• The average separation of the molecules increases

• The volume of each molecule increases

Which causes the random, zig-zag movement (Brownian motion) of smoke particles suspended in air?

• air molecules colliding with smoke particles

• convection currents as the hot smoke rises

• smoke particles colliding with each other

• smoke particles reacting with oxygen molecules in the air

A sealed gas cylinder is left outside on a hot, sunny day. What happens to the average speed of the gas molecules and to the pressure of the gas in the cylinder as the temperature of the gas rises?

• A

• B

• C

• D

A swimmer feels cold after leaving warm water on a warm, windy day. Why does she feel cold even though the air is warm?

• the less energetic water molecules on her skin escape quickly

• the more energetic water molecules on her skin do not escape quickly

• the water on her skin does not evaporate quickly enough to keep her warm

• the water on her skin evaporates quickly and cools her skin

A car tyre has a constant volume. Why does the pressure of the air in the tyre increase when its temperature increases?

• the air molecules hit each other less often

• the air molecules hit the inside of the tyre less often

• the average speed of the air molecules in the tyre is greater

• there are more air molecules in the tyre

A student places his thumb firmly on the outlet of a bicycle pump, to stop the air from coming out. What happens to the pressure and what happens to the volume of the trapped air as the pump handle is pushed in?

• A

• B

• C

• D

Some gas is trapped in a container of fixed volume. The temperature of the gas increases. Which graph shows how the pressure of the gas changes with temperature?

• A

• B

• C

• D

The volume of a gas in a sealed syringe is increased. The temperature of the gas does not change. After this change is made, what has happened to the gas molecules in the syringe?

• they move more quickly

• they move more slowly

• they hit the syringe walls less often

• the hit the syringe walls more often

The pressure of a fixed mass of a cylinder is measured. The volume of the gas in the cylinder is then slowly decreased. The temperature of the gas does not change. Which graph could show the change of pressure of the gas during this process?

• A

• B

• C

• D