Heat Energy Transfer Flashcards xx

What is heat?

Heat is a form of energy measured in joules (J).

Which direction does heat energy flow?

Heat energy flows from places of higher temperature to places of lower temperature.

Where does conduction mainly occur?

Conduction mainly occurs in solids.

What is a poor conductor of heat called?

A poor conductor of heat is called an insulator.

How is heat transferred through a non-metal such as glass?

The particles vibrate in fixed positions and pass heat energy slowly along the material.

Why do metals conduct heat faster than non-metals?

Metals contain free electrons which transfer heat energy quickly through the metal.

What are two examples of exceptional good conductors of heat?

Liquid sodium and mercury.

In the brass and wood experiment, why does the paper over the brass not scorch?

Brass conducts the heat away quickly, while wood does not.

What does the experiment with boiling water and ice show about water?

It shows that water is a poor conductor of heat because the water at the top boils while the ice at the bottom remains frozen.

What happens to the pins in the copper, aluminium, steel and glass experiment?

The pins fall off at different times because the materials conduct heat at different rates.

Which rod makes its pin fall off first?

The copper rod makes its pin fall off first.

Which rod makes its pin fall off last?

The glass rod makes its pin fall off last.

What does the pin experiment show about metals?

It shows that metals are good conductors of heat, while glass is a poor conductor.

Why does a match held close to a Bunsen flame not ignite?

Air is a poor conductor of heat, so heat is not transferred quickly through the air.

Where does convection occur?

Convection occurs in fluids, such as liquids and gases.

What happens to hot fluid during convection?

Hot fluid rises because it becomes less dense.

What happens to cold fluid during convection?

Cold fluid sinks because it is denser.

How can convection be demonstrated using a flask of water and dye?

Cold water falls while hot water rises, creating a convection current.

How does convection occur in a room heated by a radiator?

Air near the radiator becomes warm and rises. Cooler air falls and moves towards the radiator, creating a convection current.

How does a sea breeze form during the day?

The land heats up faster than the sea. Warm air above the land rises, while cooler air from the sea moves towards the land.

Why does rising air help form clouds?

Warm rising air can help form clouds as it rises upwards.

What is radiation?

Radiation is a method of heat transfer that does not require particles.

Why is radiation the only method of heat transfer that can occur through a vacuum?

Radiation does not need particles, so it can travel through a vacuum.

What type of radiation is heat radiation?

Heat radiation is infrared radiation.

What can happen to heat radiation when it reaches a surface?

It can be reflected, emitted or absorbed.

What factors affect heat emission?

Heat emission depends on the colour, type of surface, surface area and temperature.

Why are dull black surfaces better emitters of heat radiation than shiny surfaces?

Dull black surfaces emit more heat radiation than shiny silver or copper surfaces.

What are the three methods of heat transfer when heating your hands near a fire?

Convection occurs above the fire, conduction occurs through a rod placed in the fire, and radiation transfers heat to your hands from a distance.

How does a vacuum flask reduce heat transfer?

The vacuum reduces conduction and convection, while the silvered glass walls reduce radiation. The stopper and support also help reduce heat transfer.

Why does fibre filling in a sleeping bag keep you warm?

The fibres contain pockets of trapped air, and the trapped air acts as a good insulator.