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Thermal Physics Flashcards

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1
Q

Describe particle motion in solids.

A

vibration about a fixed position

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2
Q

Can solids be compressed?

A

no

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3
Q

Do solids have a fixed shape?

A

yes

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4
Q

Do solids have a fixed volume?

A

yes

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5
Q

How are the forces of attraction/bonds between molecules in a solid?

A

strong

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6
Q

How are molecules arranged in solids?

A

regular arrangement, molecules close together, tightly packed

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7
Q

Describe particle motion in liquids.

A

Particles flow and move over each other

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8
Q

Can liquids be compressed?

A

no

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9
Q

Do liquids have a fixed shape?

A

no

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10
Q

Do liquids have a fixed volume?

A

yes

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11
Q

How are the forces of attraction/bonds between molecules in a liquid?

A

weaker than in a solid

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12
Q

How are molecules arranged in liquids?

A

molecules are close together, irregular arrangement

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13
Q

Describe particle motion in gases, and the shape they take.

A

molecules are free to move, move randomly, all directions
take shape of container

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14
Q

Can gases be compressed?

A

yes

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15
Q

Do gases have a fixed shape?

A

no

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16
Q

Do gases have a fixed volume?

A

no

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17
Q

How are the forces of attraction/bonds between molecules in a gas?

A

weak forces of attraction, molecules far apart

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18
Q

What is internal energy?

A

energy of the molecules of a body

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19
Q

What is kinetic energy?

A

energy due to molecule movement

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20
Q

What is potential energy?

A

energy due to forces and separation of molecules

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21
Q

The greater the ______ of the molecules, the greater the potential energy

A

separation

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22
Q

In potential energy, what is the type of force?

A

electrical

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23
Q

solid -> liquid

A

melting

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24
Q

gas -> liquid

A

condensation

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25
Q

liquid -> solid

A

solidification
for water, freezing

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26
Q

liquid -> gas

A

boiling or evaporation

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27
Q

In order to weaken/break bonds between molecules, what do melting and boiling do?

A

absorb heat energy

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28
Q

Which processes absorb heat energy? Why?

A

melting and boiling
to weaken and break bonds between molecules and increase molecule separation

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29
Q

What happens as temperature increases, to particles?

A

they move faster

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30
Q

What is the lowest possible temperature (absolute 0)?

A

-273 celcius degrees

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31
Q

What does it mean to the particles if an object is at absolute 0?

A

particles have the least kinetic energy
- temperature at which particles in a gas exert no pressure and are no longer moving, hence not colliding with their container

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32
Q

Describe the pressure of a gas, relation to motion of its particles and their collisions with a surface.

A

moving gas molecules collide with a surface, exerting a force.

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33
Q

What is the effect of temperature on gas pressure? Why?

A

since molecules will move more quickly, they will collide with the walls of the container/surfaces more often, exerting a greater pressure
positive correlation

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34
Q

What is one piece of evidence for the kinetic particle model of matter?

A

random movement of particles in suspension

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35
Q

Describe Brownian motion.

A

Brownian motion is the random collision between particles in suspension and the particles of the gas/liquid

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36
Q

What causes pressure in gases?

A

force exerted when a particle collides with surfaces (creates F/a)

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37
Q

What is Boyle’s law?

A

For a fixed mass of gas at constant temperature, pressure is inversely proportional to volume

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38
Q

What happens to the pressure of a gas as volume increases, at constant temperature?

A

decreases

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39
Q

Why is pressure higher when volumes are smaller?

A

molecules collide off walls of the container more often.

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40
Q

What is the formula to find out pressure and volume before and after?

A

P1V1=P2V2

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41
Q

What happens to the pressure of a gas when temperature changes (volume constant)?

A

pressure increases as temperature increases

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42
Q

Why is pressure higher at higher temperatures?

A

molecules move faster and collide with container walls more often.

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43
Q

What is the equation relating degrees K and C?

A

T (in K) = 0 (in C) + 273

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44
Q

Which processes emit heat energy? Why?

A

solidification and condensation, to strengthen or make molecular bonds and decrease molecule separation

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45
Q

What is temperature, in terms of molecules?

A

measure of the average kinetic energy of the molecules of a substance

46
Q

How is the graph for P x V = constant?

A

linear, from origin

47
Q

For a fixed mass of gas at constant temperature, what is the relationship between pressure and volume?

A

P x V = constant

48
Q

What happens when a material receives heat energy, in terms of expansion?

A

molecules move faster, molecules separate further. the material will expand

49
Q

What happens when a material loses heat energy, in terms of expansion?

A

molecules move slower, molecules come close together. the material will contract

50
Q

Which state of matter expands most, for the same amount of heat energy?
Why?

A

gases, no forces of attraction between molecules, molecules have enough energy to overcome the weak intermolecular forces

51
Q

Which state of matter expands the least, for the same amount of heat energy?
Why?

A

solid, because the molecules cannot overcome the strong intermolecular forces holding the molecules together

52
Q

If a gas and a solid are subject to the same amount of heat energy, which will expand more?

A

gas

53
Q

What are 3 applications of thermal expansion in everyday life?

A

gaps in railway tracks
fitting metal tyres onto railway train wheels
bimetallic strips
thermometers

54
Q

Why are there gaps in railway tracks?

A

because it leaves space for solids to expand into when temperature increases

55
Q

How is thermal expansion used to fit metal tyres onto railway train wheels?

A

since the wheel is bigger than the tyre, the tyre is heated so it expands. this will make it possible for it to fit over the wheel. then it is cooled to contract.

56
Q

How does a bimetallic strip work?

A

two different materials on either side of a strip. when it is heated, the material which expands more will expand and cause the strip to bend (vice verse for cooling)

57
Q

What is the relative order of magnitudes of the expansion of solids, liquids and gases?

A

(least expansion) solid - liquid - gas (most expansion)

58
Q

What causes an increase in internal energy?

A

rise in temperature of an object

59
Q

In terms of molecules, what does an increase in temperature mean?

A

increased average kinetic energy of molecules of a substance

60
Q

Define the term ‘specific heat capacity’.

A

the heat energy needed for a body of mass given to increase its temperature (by 1 degree)

61
Q

What is the equation for specific heat capacity?

A

c= ∆E / m∆θ

62
Q

Describe an experiment to find out the s.h.c of water.

A
  1. connect a power pack to an ammeter, voltmeter and an electric heater
  2. measure starting temperature and mass of water (which should be in calormeter cup, with insulating air and another metal cup)
  3. turn heater on and measure the current and voltage
  4. turn heater off after 5 min, wait and measure maximum temperature
  5. find the find energy using the H = VIt formula
  6. plug results in s.h.c formula
63
Q

How do thermometers use thermal expansion?

A

mercury expands as the temperature increases

64
Q

What happens to the temperature of a substance as it goes from a solid to a liquid?

A

it will increase until the melting point is reached. the temperature stays constant until the substance is a liquid.

65
Q

What happens to the temperature of a substance as it goes from a liquid to a gas?

A

it will increase until the boiling point is reached. temperature stays constant until the substance is a gas.

66
Q

Name 3 differences between boiling and evaporation.

A

boiling only occurs at boiling point
evaporation is much slower
evaporation is only at the surface, unlike boiling which is throughout surface
boiling forms bubbles
boiling requires an external thermal energy source

67
Q

What is condensation, in terms of particles?

A

when a gas cools down, the particles move more slowly
they do not have the energy they had to overcome the intermolecular forces
particles get closer together and form a liquid

68
Q

What is solidification, in terms of particles?

A

when a liquid cools down, the particles move more slowly
they do not have the energy they had to overcome the intermolecular forces
particles get closer together and form a solid

69
Q

Define ‘evaporation’.

A

the escape of more energetic particles from the surface of a liquid

70
Q

Evaporation has a ______ effect.

A

cooling

71
Q

How does evaporation cool down a liquid?

A

molecules with a higher KE escape, leaving behind molecules with less KE. this causes the liquid to cool down.

72
Q

What is one example of evaporation’s cooling effect in real life?

A

sweating

73
Q

How does sweating work?

A

water evaporates from our skin, the temperature of the water falls, and removes heat energy from our body

74
Q

What are factors that influence the rate of evaporation?

A

temperature
wind
surface area

75
Q

How does temperature influence the rate of evaporation?

A

molecules move faster, can escape surface of liquid
increased temperature, increased rate of evaporation

76
Q

How does wind influence the rate of evaporation?

A

decreases number of molecules above the liquid surface, leaving space for them
increased wind, increased rate of evaporation

77
Q

How does surface area influence the rate of evaporation?

A

more molecules are positioned at the surface and can escape
increased surface area, increased rate of evaporation

78
Q

How is heat transferred in solids (conduction)?

A

the particles which vibrate about a fixed spot gain energy, colliding with the particles next to them and transferring thermal energy

79
Q

Define ‘conduction’
Where does it occur?

A

transfer of thermal energy from one object to another. occurs in solids

80
Q

Why are metals good thermal and electric conductors?

A

their delocalised electrons can move throughout the metal

81
Q

How does conduction occur via delocalised electrons?

A

electrons gain ke from hot end of metal, moving and colliding with atoms, increasing their KE and temp.

82
Q

Why are gases poor thermal conductors?

A

the particles are far apart, making it hard for energy to be transferred from one particle to another

83
Q

why are liquids and gases poor conductors

A

particles are too far from each other and rarely make contact to transfer energy

84
Q

What is one experiment to test conductivity?

A

put boiling water in a box with holes
place rods of different materials in these holes
place drawing pins held with petroleum jelly on the far ends of rods
see which drawing pins fall of first due to conduction of heat from water

85
Q

Define ‘convection’

A

method of thermal energy transfer in liquids and gases

86
Q

How does convection work in liquids/gases? What is the name given to this movement?

A

hot fluid expands, becomes less dense and rises
cold fluid sinks as it is more dense
the colder fluid is then heated and rises again, forming a convection current

87
Q

What is a convection current?

A

movement of fluid that transfers heat energy upwards

88
Q

Describe one experiment to test convection

A

fill a beaker with water, then place a potassium manganate crystal into the beaker
place a bunsen burned flame right under the crystal
you will see the convection from the movement of color in the beaker

89
Q

Define ‘radiation’

A

heat transfer from a hot to a colder place by infrared electromagnetic waves

90
Q

Which object emit thermal/infrared radiation?

A

all of them :)

91
Q

Does infrared radiation require a medium?

A

no, like all electromagnetic waves

92
Q

Which colours and textures are good emitters and absorbers of heat energy?

A

dark colours (black)
dull textures

93
Q

Which colours are poor emitters and absorbers of heat energy?

A

white/shiny colours

94
Q

Which colours are good reflectors of heat energy?

A

white/shiny colours

95
Q

In terms of energy, what is necessary for an object to be at a constant temperature?

A

transfer energy away from object at same rate that it receives energy

96
Q

How does the Earth’s average temperature remain constant?

A

infrared radiation energy per second absorbed from sun is balanced by i.r energy per second emitted to space

97
Q

What is one experiment to test good/bad emission of infrared radiation?

A

place two metal cans (one silver, one matte black) with hot water, a thermometer and a lid on them
observe that the black one cools down faster since they emit better

98
Q

What is one experiment to test good/bad absorption of infrared radiation?

A

take two metal cans (one matte black, one silver) with water, a thermometer and a lid on them
place them equidistantly from an electric radiant heater
black will heat up faster since it absorbs heat better

99
Q

What are two factors affecting rate of emission of radiation?

A
  • surface temperature
  • surface area
100
Q

The hotter an object is, the ____ infrared radiation it emits.

A

more

101
Q

A bigger object (larger s.a) emits ____ radiation than a smaller object (ignoring other factors)

A

more

102
Q

objects with _____ surface areas will absorb more radiation than those with ______ surface areas.

A

large
small

103
Q

applications/consequences of thermal expansion

A
  • metal railway track expand and start to curve (buckling)
  • buckling of road surfaces
  • buckling of bridges
104
Q

expansion of solids

A
  • expand slightly
  • low energy molecules overcome th strong intermolecular force
105
Q

expansion in liquids

A
  • expand more than solids
  • molecules have enough energy to partially overcome the intermolecular force
106
Q

expansion in gases

A
  • expand the most
  • molecules have high energy to overcome the intermolecular force
107
Q

what is internal energy

A

total energy stored in a system by the particles that make up the system due to their motion and positions

108
Q

what is specific heat capacity

A

Energy required to change the temperature of 1 kg of the substance by 1 °C.

109
Q

evaporation

A
  • occurs to any liquid at any temp and results in the cooling of the liquid
  • molecules that hit the surface provide energy
110
Q

melting and boiling point of water

A

0 and 100

111
Q

boiling

A
  • occurs to a liquid at certain temp and involves temperature input
  • does not result in cooling of the liquid

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