Heat transfer

What are the units for measuring energy?

• newtons

• degrees Celsius

• joules

• degrees Fahrenheit

If you leave a cup of hot tea standing in the kitchen for a whole day, what will happen?

• No energy will be transferred.

• It will gain energy from the air in the kitchen.

• Energy will be transferred from the tea to the air until the tea is the same temperature as the air.

• Energy will be transferred from the tea to the air in the kitchen, so the tea will end up colder than the air in the kitchen.

The amount of thermal energy in an object depends on three things. Which of these things does it not depend on?

• its mass

• its colour

• its temperature

• the material it is made from

Which statement about evaporation is not true?

• When some of a liquid evaporates, the liquid left is warmer than before.

• Evaporation can happen at any temperature at which the substance is a liquid.

• When some of a liquid evaporates, it is the particles moving the fastest that escape and form a gas.

• Sweating cools us down when the sweat evaporates.

Infrared radiation can travel through:

• transparent objects only.

• opaque objects only.

• empty space only.

• empty space and transparent materials.

When one end of a piece of metal is heated:

• the particles vibrate less and so the particles get closer together.

• the particles vibrate more and the vibrations are passed from particle to particle.

• the energy does not move through the metal.

• the particles get bigger.

Solids are better heat conductors than liquids or gases because:

• the particles are closer together in gases.

• the particles are closer together in liquids.

• the particles are closer together in liquids.

• the particles in a solid cannot move.

Why does the cold air near the ice lolly move downwards?

• It is colder and denser than the air further away from it.

• It is warmer and denser than the air further away from it.

• It is colder and less dense than the air further away from it.

• It is warmer and less dense than the air further away from it.

Which list of materials shows only insulating materials?

• wool, feathers, copper

• feathers, wood, carpets

• iron, copper, steel

• plastic, aluminium foil, wood

Which statement is the best explanation for why many insulating materials contain trapped air?

• trapping the air stops energy being transferred by convection

• air is a poor conductor

• trapped air makes the material lighter

• gases are poor conductors and they cannot transfer energy by convection if they cannot move.