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Physics (P.1) > Energy Transfer By Heat > Flashcards

Energy Transfer By Heat Flashcards

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0
Q

What is infrared radiation part of?

A

The electromagnetic spectrum

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1
Q

How is infrared radiation created?

A

It is emitted from hot objects

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2
Q

How can you detect the heat of an object?

A

By using infrared cameras, sensors and thermometers

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3
Q

Why are solar panels on houses often painted black?

A

Because it is a good absorber of infrared

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4
Q

Why are buildings in hot countries often painted white?

A

Because silver, white or shiny surfaces are all good reflectors of infrared

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5
Q

When does evaporation occur?

A

When liquid turns into a gas - weak attractive forces exists

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6
Q

Give three ways in which evaporation can increased?

A
  • increasing the surfaces area
  • increasing liquid temperature
  • increasing a drought of air
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7
Q

How does condensation occur?

A

When gas turns into a liquid

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8
Q

Why are metals good conductors?

A

Because they have free electrons, which vibrate when heated and transfer energy through the metal

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9
Q

Some metals are better conductors than others give an example.

A

Copper is better than iron

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10
Q

Why do metals feel cold to the touch?

A

Because they conduct the heat away from your hand

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11
Q

What is wood an example of and how does it feel?

A

It is an insulator and it feels warm to the touch

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12
Q

Give an example of a good insulator.

A

Trapped air

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13
Q

Where is trapped air used in and why?

A

Double glazing to reduce heat loss by conduction

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14
Q

What must conduction have to work?

A

Particles

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15
Q

In conduction does the heat go to cold or cold go to heat?

A

Hot to cold

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16
Q

Give three examples of insulators.

A
  • wool
  • fibre glass
  • air
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17
Q

What happens to a metal rod when heated?

A

The free electrons at the hot end gain kinetic energy and move faster

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18
Q

When does convection occur?

A

Whenever we heat fluids (a gas or liquid)

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19
Q

When are circulation currents caused?

A

When fluids rise where they are heated (as heating makes them less dence),then they move across the top of the room, after they start to fall where they cool (as cooling makes them more dence)

20
Q

Convection currents transfer energy from where to where?

A

Hot places to cold places

21
Q

Why do most fluids expand when they are heated?

A

Because the particles move about more and therefore take up more space. So that the density decrease because the same mass of fluid now occupies a bigger volume. This means that heating part of a fluid makes the part less dense and therefore it rises.

22
Q

What does diffuses mean?

A

Spread out

23
Q

Give two examples of convection current users.

A
  • gliders

- birds

24
Q

What is a fluid?

A

A gas or liquid

25
Q

What are the particles in a solid like?

A

They are next to each other in a fix position and they vibrate about their position.

26
Q

What are the forces in a solid like?

A

STRONG

27
Q

What are the particles in liquids like?

A

They move about ate random and are in contact with each other. A liquid doesn’t have its own shape and can flow

28
Q

What are the forces like in a liquid?

A

Weaker than a solid

29
Q

What are the particles like in a gas?

A

They move about randomly and are much further apart.

30
Q

What are the forces like in a gas?

A

Very small (negligible)

31
Q

Which of the following has a far less density:

Solid-liquid-gas

A

Gas

32
Q

Which of the following has particles with a lot more energy:

-solid-liquid-gas

A

Gas

33
Q

How can a substance change form one state to another?

A

By heating or cooling

34
Q

The rate at which an object transfers energy by heat depends on:

A
  • the surface are and volum
  • the material from which the object is made
  • the nature of the surface with which the object is in contact with
35
Q

How does loft insulation reduce energy transfer?

A

It reduces the rate of the energy transfer through the roof

36
Q

How does cavity wall insulation reduce energy transfer?

A

It refuses the energy through the outer walls of the building

37
Q

How does double glazing reduce energy transfer?

A

It refuse rate of energy transfer by conduction

38
Q

How does aluminium foil behind radiators reduce energy transfer?

A

It reduces energy transfer by reflecting radiation away from the wall

39
Q

How do you know if a material is a good insulator?

A

It has a lower U-value

40
Q

The bigger the temperature difference between an object and it’s surrounding, the….

A

Faster the rate at which energy is transferred by heating

40
Q

What does U-values measure?

A

How effective a material is as an insulator

40
Q

What is the process of evaporation?

A

The particles in a liquid have different energies. Some will have enough energy to escape from the liquid and become a gas. The remaining particles in the liquid have a lower average kinetic energy than before, so the liquid cools down as evaporation happens. This is why sweating cools you down. The sweat absorbs energy from your skin so that it can continue to evaporate.

41
Q

What is the process of condensation?

A

The particles in a gas have different energies. Some may not have enough energy to remain as separate particles, particularly if the gas is cooled down. They come close together and bonds form between them. Energy is released when this happens. This is why steam touching your skin can cause scalds: not only is the steam hot, but energy is released into your skin as the steam condenses.

42
Q

What affects the rate of condensation and evapouration?

A

The rate of condensation increases if the temperature of the gas is decreased. On the other hand, the rate of evaporation increases if the temperature of the liquid is increased. It is also increased if:

the surface area of the liquid is increased
air is moving over the surface of the liquid.

43
Q

What is conduction?

A

Heat energy can move through a substance by conduction. Metals are good conductors of heat but non-metals and gases are usually poor conductors of heat. Poor conductors of heat are called insulators. Heat energy is conducted from the hot end of an object to the cold end.

44
Q

Why may solar panels contain water?

A

Because the water is heated by the radiation from the sun. This water may then be used to heat buildings or provide domestic hot water

45
Q

What effects the rate of condensation?

A

The rate of condensation increases if the temperature of the gas is decreased. It is also increased if:
the surface area of the liquid is increased
air is moving over the surface of the liquid.

46
Q

What effects the rate of evaporation?

A

The rate of evaporation increases if the temperature of the liquid is increased. It is also increased if:
the surface area of the liquid is increased
air is moving over the surface of the liquid.

Physics (P.1) (9 decks)

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