Thermal Physics L1 CFU

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?

• Mass decreases, Weight decreases

• Mass decreases, Weight stays the same

• Mass stays the same, Weight decreases

• Mass stays the same, Weight stays the same

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?

• Average KE decreases, Average distance decreases

• Average KE decreases, Average distance stays the same

• Average KE increases, Average distance increases

• Average KE increases, Average distance stays the same

What are the bright dots seen through a microscope when small pollen grains are suspended in water?

• 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

Two states of matter are represented state 1: by Alana and Chloe; state 2 by Vincent and James. Alana and Chloe are running as crazy, hit walls, run back, far from each other through the whole school. James and Vincent hold hands and shiver even though it's supposed to get warmer. What is state 1 and what is state 2?

• state 1: gas, state 2: liquid

• state 1: gas, state 2: solid

• state 1: liquid, state 2: gas

• state 1: solid, state 2: liquid

The diagram represents moving gas molecules in a sealed container of fixed volume. The temperature of the gas is now increased. What happens to the pressure of the gas, and what happens to the speed of the gas molecules?

• Pressure increases, speed increases

• Pressure increases, speed unchanged

• Pressure unchanged, speed increases

• Pressure unchanged, speed unchanged

The water in a lake is at 5°C. A diver measures the pressure of the water at two different depths in the lake. He repeats the measurements on a different day when the water is at 15°C. The density of the water decreases when its temperature increases. Which combination of depth and temperature produces the greatest water pressure?

• 10m, 5°C

• 10m, 15°C

• 20m, 5°C

• 20m, 15°C

The diagram shows four labelled changes of state between solid, liquid, and gas. Which changes need an energy input? (endothermic)

• A) P and Q

• B) Q and R

• C) R and S

• D) S and P

Which diagram best shows the path of a gas molecule?

• Diagram A

• Diagram B

• Diagram C

• Diagram 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?

• A) They move more quickly.

• B) They move more slowly.

• C) They hit the syringe walls less often.

• D) They hit the syringe walls more often.