Heat and temperature: how heat moves
The difference between heat and temperature, the three ways heat moves (conduction, convection and radiation), and how insulators work. With a fair test on insulating materials.
Read
Temperature is what a thermometer measures. On the Celsius scale water freezes at 0 °C and boils at 100 °C. The particles of a hotter substance move faster.[1]
Heat is energy that moves from a hotter object to a colder one. It keeps flowing until both are at the same temperature.[2][5]
Conduction: heat passes through a material or from one object to another that touches it. Metals conduct heat well: the handle of a metal spoon in hot soup soon gets hot. Air and wood conduct heat poorly.[3][4]
Convection: in a liquid or gas, the warmer part rises and cooler fluid takes its place. You can see this in a pan of boiling water, and rising warm air replaced by cooler air makes wind.[3][2]
Radiation: heat travels as rays, even through empty space. This is how the Sun warms the Earth, and how you feel the warmth of a fire from a distance.[3][2]
Insulators slow down heat transfer. Many work by trapping air: layers of clothing, feathers, fur, polystyrene foam and double-glazed windows.[5]
Try it: Fair test: which material insulates best?
You need
- 4 identical jars or cups
- 4 thermometers (or one, read quickly in turn)
- Insulating materials: bubble wrap, cotton wool or a sock, kitchen foil, nothing
- Elastic bands
- A measuring jug
- Warm tap water (filled by the teacher)
- A timer
Safety
Warm tap water only: never hot or boiling water. The teacher pours. Glass thermometers break easily: lay them down carefully. Mop up spills.
What to do
- Wrap three jars in the different materials, using the same thickness each time. Leave one jar unwrapped as a control.
- Ask the teacher to pour the same volume of warm tap water into each jar. Put a lid or a piece of card on top.
- Measure the starting temperature of each jar.
- Measure the temperature every 5 minutes for 20 minutes.
- Fair test: change only the material. Keep the jars, the amount of water, the starting temperature and the place the same.
- Work out how many degrees each jar cooled down. Plot a line graph of temperature against time.
Play: Conduction, convection or radiation?
How does the heat travel in each example?
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Quiz
Other ages: Ages 6–7 · Ages 15–16