IGCSE - P3+P4 revision

A liquid at room temperature is put on a metal surface which is also at room temperature. A student blows gently across the liquid and its temperature decreases. What causes the liquid to become cooler?

• Bubbles of water vapour form in the liquid and go into the air.

• The moving air reduces the kinetic energy of all the particles in the liquid.

• Thermal energy flows from the liquid into the metal.

• The more energetic particles in the liquid escape into the air.

The liquid level in a thermometer rises when the thermometer is placed in hot water. What causes this?

• The liquid contracts.

• The liquid evaporates.

• The liquid expands.

• The liquid freezes.

Which statements correctly describes a liquid that is boiling

• no bubbles seen, takes place on the surface only

• no bubbles seen, takes place throughout the liquid

• bubbles seen, takes place on the surface only

• bubbles seen, takes place throughout the liquid

Which statement about boiling and evaporation is correct?

• Boiling requires a supply of thermal energy but evaporation does not.

• Evaporation takes place at the surface of a liquid but boiling takes place throughout the

  liquid.

• When water boils in a kettle, its temperature decreases.

• When water evaporates, its temperature increases.

Why are small gaps left between the metal rails of a railway track?

• to allow for expansion of the rails on a hot day

• to allow for contraction of the rails on a hot day

• to allow for expansion of the rails on a cold day

• to allow for contraction of the rails on a cold day

A metal rod is heated at end X. Why does end Y of the metal rod become hot?

• Energy is transferred from end X of the rod to end Y by vibration of positive ions and by

  movement of electrons.

• Energy is transferred from end X of the rod to end Y by movement of positive ions only.

• Energy is transferred from end X of the rod to end Y by vibration of positive ions only.

• Energy is transferred from end X of the rod to end Y by movement of electrons only.

The air in a room is heated by a heater. The diagram shows the circulation of the air in the room. Which statement about the air that is heated is correct?

• The air contracts and become less dense

• The air contracts and becomes more dense

• The air expands and becomes less dense

• The air expands and becomes more dense

In a refrigerator, the cooling unit can be fitted either at the top or at the bottom. In an oven, the heater can be fitted either at the top or at the bottom. Which row shows the best position for the cooling unit and the best position for the heater?

• A

• B

• C

• D

Tom sits near a campfire and he feels warm. How does heat transfer from the campfire to him?

• By conduction only

• By radiation only

• By convection only

• By conduction and radiation

Which row shows the surface that is the better absorber and the surface that is the better emitter of infra-red radiation?

• A

• B

• C

• D