Heat

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4

Why are gaps left in pavements, railway tracks, and floor boards?

Why are electricity cables left slack?

Why are bottles of minerals not filled up to the top?

Because materials expand when they

heat up we need to leave room for that.

Slide 30

Expansion V Contraction

The reason materials expand when heated is because the heat gives the molecules energy and as a result they begin to move, leaving them further apart and hence the material expands

Cooling has the opposite effect, the particles move closer together causing the molecules to contract

One exception: water expands when cooled

Slide 31

Revision

1. Which of the following is not a method of heat transfer?

A. Radiation

B. Insulation

C. Conduction

D. Convection

Slide 32

Revision

1. Which of the following is not a method of heat transfer?

A. Radiation

B. Insulation

C. Conduction

D. Convection

Slide 33

2. In which of the following are the particles closest together?

A. Solid

B. Liquid

C. Gas

D. Fluid

Slide 34

2. In which of the following are the particles closest together?

A. Solid

B. Liquid

C. Gas

D. Fluid

Slide 35

3. How does heat energy reach the Earth from the Sun?

A. Radiation

B. Conduction

C. Convection

D. Insulation

Slide 36

3. How does heat energy reach the Earth from the Sun?

A. Radiation

B. Conduction

C. Convection

D. Insulation

Slide 37

4. Which is the best surface for reflecting heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

Slide 38

4. Which is the best surface for reflecting heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

Slide 39

5. Which is the best surface for absorbing heat radiation?

A. Shiny white

B. Dull white

C. Shiny black

D. Dull black

Slide 40

5. Which is the best surface for absorbing heat radiation?