# Understanding Heat Transfer, Conduction, Convection and RadiationPage 1

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Understanding Heat Transfer, Conduction, Convection and Radiation

Slide 2

## Heat Transfer

Heat always moves from a warmer place to a cooler place.

Hot objects in a cooler room will cool to room temperature.

Cold objects in a warmer room will heat up to room temperature.

Slide 3

Question

If a cup of coffee and a red popsickle were left on the table in this room what would happen to them? Why?

The cup of coffee will cool until it reaches room temperature. The popsickle will melt and then the liquid will warm to room temperature.

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## Heat Transfer Methods

Heat transfers in three ways:

Conduction

Convection

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Conduction

When you heat a metal strip at one end, the heat travels to the other end.

As you heat the metal, the particles vibrate, these vibrations make the adjacent particles vibrate, and so on and so on, the vibrations are passed along the metal and so is the heat. We call this?

Conduction

Slide 6

Metals are different

The outer e of metal atoms drift, and are free to move.

When the metal is heated, this ‘sea of electrons’ gain k _ energy and transfer it throughout the metal.

Insulators, such as w _ and p , do not have this ‘sea of electrons’ which is why they do not conduct heat as well as metals.

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Slide 7

Why does metal feel colder than wood, if they are both at the same temperature?

Metal is a conductor, wood is an insulator. Metal conducts the heat away from your hands. Wood does not conduct the heat away from your hands as well as the metal, so the wood feels warmer than the metal.

Slide 8

Convection

What happens to the particles in a liquid or a gas when you heat them?

The particles spread out and become less dense.

This effects fluid movement.

What is a fluid?

A liquid or gas.

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Fluid movement

Cooler, more d , fluids sink through w _, less dense fluids.

In effect, warmer liquids and gases r _ up.

Cooler liquids and gases s _.

ense

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ink

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