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Physics P1 ~ AQA > P1.1 ~ Energy Transfer > Flashcards

P1.1 ~ Energy Transfer Flashcards

1
Q

What is infrared radiation?

A

Thermal (infrared) radiation is the transfer of thermal energy (heat energy) by electromagnetic waves; no particles of matter are involved

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2
Q

What do all objects do?

A

Emit and absorb thermal radiation

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3
Q

What happens if an object is hot?

A

More energy will be radiated

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4
Q

What does the amount of thermal radiation given out depend on?

A

It’s surface, shape and dimensions.

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5
Q

What would cause an object to absorb energy faster?

A

A big difference in temperature between the object and its surroundings.

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6
Q

How can the rate of heat transfer be slowed?

A

By the use of insulation, which provides a barrier.

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7
Q

How do different materials (dark matt surfaces and light shiny surfaces) transfer heat at different rates?

A

At the same temperature:
~ dark matt surfaces emit more radiation than light shiny surfaces
~ dark matt surfaces absorb more radiation than light shiny surfaces because light shiny surfaces are good reflectors of infrared radiation

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8
Q

What is the kinetic energy in solids like?

A

Solid partials have the least amount of energy. They are not able to move but do vibrate around a fixed point.

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9
Q

How does heating a solid affect the kinetic energy?

A

Heating a solid gives the particles enough energy to move around (although they cannot move far apart) and it melts to become a liquid.

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10
Q

How can heating a liquid affect the kinetic energy of the particles?

A

Further heating can give the particles enough energy to move very quickly. They separate from each other and the liquid evaporates to become a gas.

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11
Q

What is conduction?

A

Conduction is the transfer of heat energy without the substance itself moving.

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12
Q

What structure is a good conducter?

A

Metals

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13
Q

What happens when a metal becomes hotter?

A

It’s tightly packed particles gain more kinetic energy and vibrate. The energy is transferred to cooler parts of the metal by delocalised electrons, which move freely through the metal, colliding with particles and other electrons

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14
Q

Why can conduction occur in non-metal solids?

A

Because the particals can pass energy from one to the next by vibration.

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15
Q

Why are non-metals poor conductors?

A

Due to the lack of free electrons.

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16
Q

Why are gases poor conductors?

A

Because the particles are so far apart.

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17
Q

What is convection?

A

Convection is the transfer of heat energy through movement.

18
Q

Where does convection occurs?

A

In liquids and gases.

19
Q

What can convection create?

A

Convection currents.

20
Q

What is condensation?

A

When the particles in a gas have more energy than those in a liquid. When a gas condenses to form a liquid, this energy is released and can make the temperature increase.

21
Q

When can condensation occur?

A

When a warm gas comes in contact with a cold surface.

22
Q

When does evaporation occur?

A

A liquid evaporates when it’s particles have gained enough energy to escape the surface of the liquid and become a gas.

23
Q

What are key features of a vacuum flask?

A

~ They are usually made from plastic which is a poor conducter
~ Shiny silver sides which reflect infrared radiation and stop heat transfer.
~ A vacuum, which contains no particles so neither conduction not convection can take place
~ A screw top, this can prevent evaporation from the surface and convection currents at the top.

24
Q

What is a U-Value?

A

The U-Value of a material indicates how effective a material is as an insulator because it can show how quickly heat energy can pass through.

25
Q

Is it better to have a lower or higher U-Value? (and why?)

A

A low U-Value.
Because that it means that heat flows through it slowly. Therefore the lower the U-Value, the better the material is at insulating.

26
Q

What is the equation to find the payback time?

A

Total cost of improvement
Payback ————————–
Time = Savings per year

27
Q

What is the specific heat capacity of a substance?

A

The amount of energy needed to change the temperature of one kilogram of it by one degree Celsius.

28
Q

What happens if something (e.g water) has a high specific heat capacity?

A

It can store a lot of heat energy without getting too warm. This makes it useful as a coolant.

29
Q

How is heat transferred from homes into the environment?

A

Conduction ~ though the walls, floor, roof and windows
Convection ~ convection currents coupled with cold drafts from gaps in doors and windows cause heat energy carried by warm air to rise up to the roof space where it is easily lost
Radiation ~ from the surface of the walls, roof and through the windows.

30
Q

Where is heat lost?

A 
Roof ~ 25%
Under doors and windows ~ 15%
Walls ~ 35%
Windows ~ 10%
Floor ~ 15%
31
Q

How can you prevent heat being lost through the roof?

A

Roof insulation ~ traps a layer of air between fibres or insulating material.

32
Q

How can you prevent heat from being lost through under doors and windows?

A

Draught excluders ~ keep as much warm air inside as possible.

33
Q

How can you prevent heat loss through walls?

A

Cavity wall insulation and internal thermal boards.

34
Q

How can you prevent heat loss through windows?

A

Double glazing ~ traps air between two sheets of glass.

Curtains ~ stop heat loss through convection.

35
Q

How can you prevent heat loss through the floor?

A

Carpets, rugs and underfloor insulation can stop heat loss through the floor.

36
Q

Advantages and disadvantages of roof insulation?

A

Advantages
~ can reduce heat loss by 20%
~ many different methods to suit all homes
~ short payback time
Disadvantages
~ requires suitable safety precautions to be taken, e.g. Wearing dust mask

37
Q

Advantages and disadvantages of draught excluders?

A 
Advantages 
~ can reduce heat loss by upto 15%
~ cheap and easy to install
~ short payback time
Disadvantages
~ must make sure that air vents are not blocked - fresh air needs to circulate to prevent dry rot.
38
Q

Advantages and disadvantages of cavity wall insulation?

A 
Advantages
~ can reduce heat loss by 35%
Disadvantages
~ expensive 
~ long payback time
39
Q

Advantages and disadvantages of double glazing?

A

Advantages
~double glazing traps are between two sheets of glass
Disadvantages
~double glazing can reduce heat loss by up to 10%

40
Q

Advantages and disadvantages of curtains?

A

Advantages
~Curtains are cheap and easy to install
Disadvantages
~There are none

41
Q

Advantages and disadvantages of carpets?

A

Advantages
~carpets and rugs are easy to install
Disadvantages
~underfloor insulation is expensive and has a long insulation time

Physics P1 ~ AQA (5 decks)

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