P3 Thermal Physics

A cup contains hot liquid.

Some of the liquid evaporates.

What happens to the mass and what happens to the weight of the liquid in the cup?

• A

• B

• C

• D

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.

A 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.

A liquid is evaporating. The liquid is not boiling.

Which statement about the liquid is correct?

• Any molecule can escape, and from any part of the liquid.

• Any molecule can escape, but only from the liquid surface.

• Only molecules with enough energy can escape, and only from the liquid surface.

• Only molecules with enough energy can escape, but from any part of the liquid.

The diagram shows a quantity of gas enclosed in a cylinder by a piston.

The piston is moved to the left or to the right. The temperature of the gas is kept constant.

Which row describes the effect of moving the piston slowly in the direction shown in the table?

• A

• B

• C

• D

What 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 bottle of constant volume contains air.

The air in the bottle is heated by the Sun.

What is the effect on the average speed of the air molecules in the bottle, and the average distance between them?

• A

• B

• C

• D

Air in a sealed syringe is slowly compressed by moving the piston.

The temperature of the air stays the same.

Which statement about the air is correct?

• The pressure of the air decreases because its molecules now travel more slowly.

• The pressure of the air decreases because the area of the syringe walls is now smaller.

• The pressure of the air increases because its molecules now hit the syringe walls more frequently.

• The pressure of the air increases because its molecules now travel more quickly.

Very small pollen grains are suspended in a beaker of water. A bright light shines from the side. Small, bright dots of light are seen through a microscope. The dots move in rapidly changing, random directions.

What are the bright dots?

• pollen grains being hit by other pollen grains

• pollen grains being hit by water molecules

• water molecules being hit by other water molecules

• water molecules being hit by pollen grains

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