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Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed.

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Page 1: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Heat can travel by Convection

A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed.

Page 2: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Examples of Convection

Page 3: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Heat cannot travel in solids by convection.

Why?

Page 4: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Heat can travel by Conduction

Hot particles vibrate more, so collide with adjacent particles. The heat energy travels from hot to cooler areas.

hot cold

Page 5: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Heat can travel by Conduction

Metals are good conductors of heat

Why?

Page 6: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Heat can travel by Conduction

Metals are good conductors of heatThey have

free electrons that can move from atom to atom carrying

thermal energy too

Page 7: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Heat can travel by Conduction

Most gases are poor conductors of heat (insulators)

Why?

Page 8: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Heat can travel by Conduction

Gases are poor conductors of heat (insulators)

The atoms are too far apart for the vibrations to be passed easily.

Page 9: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

There’s one other way!

¡Uno mas!

Page 10: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Infrared radiation

Page 11: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Infrared radiation

Heat can travel by infrared radiation (“Hot light”!)

Page 12: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Infrared radiation

Infrared radiation can travel through a vacuum (and through air)

Page 13: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

An experiment!

Can you gather again around Mr

Porter?

Page 14: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Infrared radiation

Black objects are good absorbers of infrared radiation.

Page 15: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Infrared radiation

Shiny objects reflect infrared radiation.

Nottingham Forest winning the champions league in 1979

Page 16: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Infrared radiation

Black objects are good EMITTERS of IR radiation

100°C 100°C

Shiny!

Page 17: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Vacuum Flask (“Thermos”)

Page 18: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

The insulated lid stops the heat escaping (and entering) by convection

Page 19: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

The vacuum between the two walls stops the heat escaping (and entering) by conduction

vacuum

Page 20: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

The silvered inner and outer stops the heat escaping (and entering) by radiation

silvered outer

silvered inner

Page 21: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

This means hot liquids stay hot because the heat cannot escape

Hot chocolate

Page 22: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

This means cold liquids stay cold because the heat cannot enter

Cold Vimto

Page 23: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

In reality, some heat escapes via the lid and eventually the liquid inside will become the same

temperature as the surroundings

Page 24: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

In a perfect flask without a lid, a hot drink would stay hot forever!

Hot chocolate

Page 25: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

The vacuum flask

Can you complete the sheet please?

Page 26: Heat can travel by Convection A hot fluid expands, so is less dense, so rises. Cold fluid takes its place. A convection current can be formed

Other methods of insulation?

• Can you think of FIVE other examples of heat insulation? Draw a diagram for each one and two sentences of explanation explaining how it works.


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