p1.1-p1.3 Flashcards

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1
Q

Which surfaces absorb and emit infra red radiation the most?

A

Black matt surfaces

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2
Q

Which surfaces absorb and emit infra red radiation the least?

A

Light shiny surfaces

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3
Q

What colours absorb the most heat?

A

Dark

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4
Q

What colours reflect the most heat?

A

Light

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5
Q

What are the most efficient radiators made of?

A

Matt black materials

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6
Q

How do solar water heaters work?

A

Water pipes under a black surface
(zig zag pattern to increase SA)
Absorbs radiation from the sun (conduction)
Heats water (convection)
–> Water used for washing or pumped into radiators

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7
Q

Why are water pipes in a solar water heater in a zig-zag pattern?

A

To increase SA

–>Allows more conduction

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8
Q

What is heated water from a solar water heater used for?

A

Washing

Pumped into radiators

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9
Q

What happens to the amount of radiation that an object emits if it is hotter than it’s surroundings?

A

Emits more radiation than it absorbs

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10
Q

what happens to amount of radiation emitted by an object that is colder than its surroundings?

A

Emits less than it absorbs

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11
Q

Define a vacuum

A

A space with no particles

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12
Q

What are the three ways of transferring heat energy?

A

Conduction

Convection

Radiation

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13
Q

What two types of transferring heat energy uses particles?

A

Conduction

Convection

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14
Q

How is the speed of energy transferred by heating changed by the size of the difference in temp between an object and its surroundings?

A

Bigger temp difference=Faster

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15
Q

Which state of particles has the most density?

A

Solids

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16
Q

What state of particles has the most energy?

A

Gases

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17
Q

Use kinetic theory to describe the particles within a solid

A

Particles in a fixed, regular shape
Vibrate in position (only movement)
Strong forces of attraction at a distance
Repulsed when close together (–>so can’t be compressed)
Strong bonds between particles
–> shape is fixed, can’t be compressed

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18
Q

In what state of matter does conduction occur?

A

Solids
Liquids
Gases

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19
Q

What state and type of atom does conduction occur most efficiently?

Why?

A

Metals

Have free electrons

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20
Q

Describe the process of heat energy being transferred by conduction

A
Particles at one end are heated 
(+KE)
-->Will vibrate (more the more energy recieved)
-->Will knock into other particles
-->Will transfer KE on

–>CREATES CHAIN REACTION–>energy spread through matter

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21
Q

Use kinetic theory to describe why gases are poor conductors

A

In gases: lots of space between particles

–>Less likely to knock into each other and transfer KE

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22
Q

How does double glazing work?

A

Air between two sheets of glass

–>minimises conduction of heat through the glass

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23
Q

Why do particles change state when heated?

A

More energy=more movement

  • ->Eventually: will break free of bonds holding them in a fixed/random position
  • ->BECOMES LESS DENSE AS MOVE AWAY FROM EACH OTHER
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24
Q

Use kinetic theory to explain how particles in a liquid are arranged and how this affects their properties

A

Arranged in random patterns
Medium forces between particles
–>little space between particles (hard to compress)
Have medium amounts of energy
–>Slide past each other (ALWAYS TOUCHING OTHER PARTICLES)
(FLUID)

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25
Q

Use kinetic theory to describe particles in a gas are arranged and how this determines the properties of gases

A

High energy
Weak forces between particles (bonds broken)
–>Lots of space between particles (EASY TO COMPRESS)
–>Free to move at high energy (WILL FILL A SPACE)

26
Q

In what states of matter does convection occur?

A

Liquids

Gases

27
Q

Explain the process of convection

A

Particles at the bottom of a container are heated
–>Gains energy–>Becomes less dense–>WIll rise to the top
As they move upwards, particles will loose energy
–>Become more dense–>Will fall back to the bottom
Heated again at the bottom
–>CYCLE CONTINUES

28
Q

What common appliances rely on convection currents to heat and cool things?

A

HEAT
Radiators

COOL
Fridges

29
Q

How is heat energy transferred to solids in order for them to melt?

A

Conduction

30
Q

How is heat energy transferred to liquids in order to evaporate?

A

Convection

31
Q

Which method of transferring heat energy out of convection and conduction more efficient?

A

Convection

32
Q

Can particles in a liquid evaporate below their boiling point?

A

Yes

–>Individual particles can escape below the point that all particles in the liquid will boil

33
Q

What are the two conditions that alter whether a particle can evaporate below BP?

A

Particles must be travelling in the right direction

Particles must be travelling fast enough to overcome attractive forces of other particles in the liquid

34
Q

What happens to the average KE and speed of particles in a liquid when a particle evaporates?

What is the result of this?

A

Decrease

Liquid cools

35
Q

What is condensation

A

Particles in a gas loosing enough KE and speed that attractive forces pull them closer together, and they change state into a liquid

36
Q

What must happen to particles in a gas in order to condense?

A

Loose:
KE
Speed

(both depend on KE levels)

37
Q

How do you increase the rate of evaporation?

A

Increase airflow above the liquid
Increase the temp
Increase the SA of the liquid
Lower density

38
Q

How do you increase the rate of condensation?

A

Lower airflow
Lower temp of gas
Lower temp of the surface that the gas touches
Increase density

39
Q

State methods used to reduce the transfer of kinetic energy by conduction

A

Create a vacuum

Use good insulators

40
Q

State the only method that can be used to reduce the transfer of heat by convection?

A

Enclose the liquid/gas

put a lid on

41
Q

State a method of reducing the transfer of heat by radiation

A

Use silvery surfaces above matt black ones

42
Q

Describe and explain the factors affecting the rate of transfers of heat energy

A

SA/V
–>Bigger=more IR waves can be emitted
=transfer quicker

TYPE OF MATERIAL
–>If object in contact w a good conductor–>heat will be conducted away more easily
(as good conductors transfer heat quicker than insulators)

43
Q

What is the effect of more effective methods of insulation in homes?

A

Will have the largest annual saving

44
Q

What is the equation for payback time?

A

Initial investment/Annual saving

45
Q

Define payback time

A

How long it takes for the investment a person has made to be equal to the money they have saved due to that investment

46
Q

What is the use of draught proofing in a house?

What is it?

A

Reduces heat lost to convection

Strips of foam secured around doors and windows

47
Q

What is loft insulation?

What method(S) of heat loss does this reduce?

A

Foam squirted into gaps between bricks

Reduces convection, conduction and radiation

48
Q

What kind of heat loss does having a thick curtain reduce?

How?

A

Convection and conduction

Creates an air gap between room and window

49
Q

How does a hot water tank jacket reduce heat loss and save money?

What methods of transferring heat does it reduce?

A

Covers and insulates hot water tank

Conduction and radiation

50
Q

What do U-values show?

A

How fast heat is transferred through a material

51
Q

What does a low U-value indicate about the insulation of a material?

A

Better

52
Q

What does specific heat capacity show?

A

Amount of energy required to raise the temp of 1kg of a substance by 1 degree c

53
Q

What is the rearranged equation to calculate SHC?

A

Energy/Mass*Temp change

54
Q

What is the SHC of water?

A

4.2KJ/KgDegreeC

55
Q

What does a high SHC indicate about how good something is at storing heat?

A

Better than low

56
Q

Why do materials used for heaters have a high SHC?

A

They can store high amounts of energy without warming up themselves

57
Q

Describe how solar panels work

A

IR absorbed from sun

Travels into pipes of water–>HEATS

58
Q

What are the advantages of using solar panels?

A

No pump needed–> Heat will move by convection

IR can be absorbed even in cold weather

59
Q

How do solar cells work?

A

Absorb Vl from sun

–>Directly produces electricity

60
Q

What are the advantages of using solar cells?

A

Light can still be harnessed on a cloudy day