Three ways heat travels

The idea

Heat is transferred in three ways—conduction, convection and radiation; conduction and convection need a material medium whose particles help transfer heat, whereas radiation needs no material medium.

A pan of water

Water is being heated in a pan on a flame. A teacher or adult does this. Heat reaches the pan, the water and the air around.

Is heat moving in the same way in all three places?

• No, there are three different ways
• Yes, only one way
• Heat does not move here at all

Three places, three ways

Tap each place: the pan base, the water inside, and the warmth around.

Conduction, convection, radiation

In the pan base the heat is passed from particle to particle. In the water the particles move and carry heat. The warmth around us comes straight from the hot objects, with no medium.

Heat is transferred in three ways: conduction, convection and radiation. Conduction and convection need a material medium whose particles help transfer heat, whereas radiation needs no material medium.

• Way | Particles | Medium needed?
• Conduction | Stay in place, pass heat on | Yes
• Convection | Move from place to place | Yes
• Radiation | None involved | No

Notes

Heat is transferred in three ways: conduction, convection and radiation. Conduction and convection need a material medium whose particles help transfer heat, whereas radiation needs no material medium.

Check yourself

How does heat get from the flame to the pan?

How is the water in the pan heated?

Which way of heat transfer needs no material medium?

We feel warmth around a hot pan without touching it. This is due to …

• By convection. Convection happens in liquids and gases. The pan is a solid.
• By precipitation. Precipitation is rain, snow and hail, not a way of heat transfer.
• By conduction — correct. Yes!
• By convection — correct. Yes!
• By conduction only. The water particles move and carry heat, so it is convection.
• By radiation only. Radiation is the way the warmth reaches us around the pan.
• Conduction. Conduction needs a material medium, whose particles pass the heat on.
• Radiation — correct. Yes!
• Convection. Convection needs a liquid or a gas whose particles move.
• conduction. Conduction needs touch or contact between particles. The warmth around the pan is due to radiation.
• evaporation. Evaporation is a liquid turning to vapour, not a way of heat transfer.
• radiation — correct. Yes!