How heat moves
Why does a metal spoon in hot soup get hot, but a wooden spoon does not?
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Explain
Heat moves from hot to cold.
Metal lets heat through quickly.
Heat moves in three ways.
Conduction passes heat along through a solid. Metals are very good at this. Convection is heat carried by moving air or water.
Radiation is heat carried by waves, even through empty space. That's how the Sun warms us.
In conduction, energy passes between neighbouring particles. Free electrons make metals especially good conductors.
In convection, warm fluid expands, becomes less dense and rises, and cooler fluid sinks to take its place. Radiation is infrared light, and needs no material.
Example: a pan on a hob uses conduction through the base and convection in the water.
- Conduction through solids
- Convection in liquids and gases
- Radiation through space
Want the full story?
The sim shows only conduction, with simple illustrative rates. Air is a poor conductor, so trapped air makes a great insulator. That is why fur, wool and double glazing all work.
Try it at home
Ask a grown-up to help
You need a metal spoon, a wooden spoon, a mug of warm (not hot) tap water.
You need: a metal spoon, a wooden spoon, a mug of warm (not hot) tap water.
Hold a metal spoon, then a wooden spoon.
- Stand both spoons in a mug of warm tap water.
- Wait 2 minutes.
- Touch the handles.
What's happening: metal conducts heat well, so the handle warms up. Wood is an insulator.
Physics is life
Your body
Your blood carries heat around.
Daily life
Coats keep heat in.
Nature
Warm air makes the wind.
Space
The Sun warms us through space.
Quick check
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Words to know
Conduction: Heat passing through a material, from particle to particle.
- Conduction
- Heat passing through a material, from particle to particle.
- Convection
- Heat carried by moving liquid or gas.
- Radiation
- Energy moving as waves, even through empty space.