3 Types of Heat Transfer3 Types of Heat Transfer

Heat Transfer-Heat Transfer-

The movement of The movement of heat from a warmer heat from a warmer object to a cooler object to a cooler object.object.

1. Conduction1. Conduction

Heat transfer by direct Heat transfer by direct contact of molecules.contact of molecules.

In other words, when one In other words, when one molecule runs into molecule runs into another and it runs into another and it runs into another, etc.another, etc.

It can occur in a solid, It can occur in a solid, liquid or a gas.liquid or a gas.

Occurs best in a solid Occurs best in a solid because the molecules because the molecules are close together.are close together.

conductionconduction

2. Convection2. Convection

Heat transfer by Heat transfer by means of up and means of up and down movements down movements called convection called convection currents.currents.

Can occur only in a Can occur only in a liquid or a gasliquid or a gas

Convection currentsConvection currents Heated molecules do 2 Heated molecules do 2

things:things: 1. they expand, become 1. they expand, become

less and then..less and then.. 2. they rise.2. they rise.Cooled molecules do the Cooled molecules do the

exact opposite:exact opposite: 1. they contract, become 1. they contract, become

more dense and then…more dense and then… 2. they sink2. they sinkThat is what makes a hot air That is what makes a hot air

balloon rise.balloon rise.

3. Radiation3. Radiation

Heat transfer through Heat transfer through open space.open space.

Occurs in a gas only.Occurs in a gas only.