Heat transfer and sources

Introduce heat (also called thermal energy), and that it can move from place to place.
It can move by Radiation (as waves, like light), Conduction (between materials that are touching) and Convection (flowing in a gas or liquid).
Ask students to rub their hands together to make heat by friction.
Brainstorm on sources of heat.

Do a selection of the activities.

My favourite sequence:
Use a heat lamp in a circle to introduce radiation.
Look at IR images together and discuss sources of radiation.
Hand out Heat sensitive sheets to introduce conduction.
Allow free play with the sheets (using the heat lamps to charge them), so exploring radiation and conduction.
End back at the circle for a convection demonstration.

Activity descriptions:

Heat sensitive sheets are super fun and demonstrate conduction and radiation (but are expensive).
Outdoors on a sunny day, the sun heats them up with its radiation. Warm playground equipment or walls can heat them up by conduction. Shadows or cool water make patterns on them.
Indoors, heat lamps heat the sheets up by radiation. By touching classroom surfaces they are cooled down by conduction.
The sheets can also be used to demonstrate heat transfer through a conductor (e.g. tin foil) and an insulator (e.g. felt).

Activities that show different ways that heat can move:
Convection activity: heat convection demonstration (can use hot water from a thermos if outdoors).
Convection activity indoors (where there are no drafts): candle heat pinwheel
Radiation indoors: infra red heat lamp demonstration then free play with heat sensitive sheets (radiation and conduction).
Heat sensitive sheets can be heated up by radiation from a lamp, and cooled by conduction.
Conduction activity (needs electric kettle, so indoors easiest): heat conduction in different materials.

Heat sources activity.
Show infra red camera images to show sources of infra red radiation (e.g. a house with windows radiating heat, a dog with heat radiating from parts of its body, also IR images of galaxies).

End by summarizing ways that heat can travel.
Both conduction and convection need molecules to transfer the heat energy.
Radiation does not need molecules. The sun is a source of radiation and travels through the vacuum of space to reach Earth.

Explain that heat transfer makes our weather and our ocean currents:
Heat radiation from the sun heats up the Earth. The warm molecules of the ground heat up the air molecules above it by conduction. The warm air molecules move upwards by convection. The warm air moving up has gas water molecules in it, which cool as they rise to form clouds, which make rain - the water cycle! When warm air moves upwards, air moves sideways to replace it, which creates winds.
In our oceans warm water rises and flows on the surface. Other water moves to take its place. This mass movement of water caused by heat transfer (as well as salt differences) creates our global ocean currents. Water holds a lot of heat without getting warmer (it has a high "heat capacity"), so ocean water keeps the temperatures moderate in adjacent areas.