P14: Energy Transfer by Heating Flashcards Preview

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Flashcards in P14: Energy Transfer by Heating Deck (20)
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1
Q

What is the role of free electrons?

A

> When a metal is heated, the FE in the heated part gain kinetic energy, and move faster.

> These FEs diffuse and collide with other FE and ions in the cooler parts of the metal.

> As a result, kinetic energy is transferred into these new FE’s.

2
Q

What are the best conductors of energy?

A

Metals (contain free electrons)

3
Q

What are the best insulators?

A

Wool and Fibreglass (insulating air pockets)

4
Q

Convection

A

Circulation of a liquid or gas caused by increasing its thermal energy.

5
Q

Convection only takes place in…

A

… fluids because of circulation within a fluid.

6
Q

Why does convection occur when a substance is heated?

A

Heating a fluid makes it less dense, which will cause it to rise. This pushes cooler fluid to the bottom where it is also heated, etc etc.

7
Q

Evaporation

A

When particles escape the surface of the fluid and entre the air.

8
Q

How does evaporation cool a substance?

A

> Relatively weak forces of electrostatic attraction exist between the particles of a liquid.

> The faster particles with more kinetic energy break away from the particles at the surface and escape through evaporation.

> This leaves the liquid cooler because the average kinetic energy of each particle has decreased.

9
Q

The higher the temperature of an object…

A

… the more infrared radiation it emits at a given time.

10
Q

What is infrared radiation?

A

Energy transfer by electromagnetic waves.

11
Q

Do all human bodies emit or absorb infrared radiation?

A

Both

12
Q

What are the best surfaces for absorbing radiation?

A

Dark, Matt Surfaces

13
Q

What are the best surfaces for reflecting infrared radiation?

A

Light, Shiny Surfaces.

14
Q

Why do dark matt surface absorb Infrared radiation Better?

A

The surface has lots of cavities.

15
Q

What are the best surfaces for emitting infrared radiation?

A

Dark, Matt Surfaces.

16
Q

The bigger the temperature difference between an object and its surroundings…

A

… The faster the rate at which energy is transferred.

17
Q

3 factors the rate of energy transfer relies on.

A

> Shape, size and material of an object.

>Nature of the surface that the object is in contact with.

> Temp. diff between an object and its surroundings.

18
Q

Expansion by heating

A

THe expansion of a substance due to increasing its temperature.

19
Q

Which state expands the most when heated?

A

Gas

20
Q
A