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The final mock (Physics) > Unit 3.4 Thermal Physics > Flashcards

Unit 3.4 Thermal Physics Flashcards

1
Q

What is internal energy?
(3 things)

A
  • Sum of the random distribution
  • of kinetic & potential energies
  • in a substance (solid, liquid and gas)
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2
Q

What is KE in a substance?
(2-way)

A
  • Energy a substance has
  • due to the movement of the ptcls in it
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3
Q

What is PE in a substance?
(3-way)

A
  • Energy a substance contains
  • due to the breaking of bonds
  • & overcoming molecular attractive forces
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4
Q

Tell me about the changes of state
(2-way + 2-way)

A
  • As temp of a substance rises
  • changes state
  • Internal energy also rises
  • BUT, KE & PE don’t rise simultaneously
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5
Q

Describe the heating curve from points A - F
(5 points to describe)
(It’s probably better if u draw it)

A
  • A - B = rise
  • B - C = constant
  • C - D = rise
  • D - E = constant
  • E - F = rise
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6
Q

From the heating curve, why does the temp. remain constant at some points?
(1 + 2-way)

A
  • KE remains constant
  • PE increasing as
  • intermolecular forces are overcome
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7
Q

From the heating curve, which letter does KE only increase?
(3 things)

A
  • None
  • KE increases as temp. increase
  • PE increases as ptcls move further apart
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8
Q

Which letters does only PE increase?
(3 things)

A
  • B - C & D - E
  • as KE doesn’t increase due to temp. = constant
  • PE increases as intermolecular forces = overcome
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9
Q

From the heating curve, which points have both KE & PE increasing?
(3 things)

A
  • A - B
  • C - D
  • E - F
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10
Q

State the relationship between temperature and KE?

A

Directly proportional
(Ek ∝ T)

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11
Q

Describe the process of melting using simple kinetic model
(3 things)

A
  • Bonds breaking
  • Particles no longer fixed in place
  • Can move around each other
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12
Q

Describe the process of boiling using simple kinetic model
(2 things)

A
  • All bonds broken
  • Particles are completely free
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13
Q

Describe the process of evaporating using simple kinetic model
(2 things)

A
  • Particles at the surface of the substance
  • break all bonds and become free
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14
Q

From heating curve, describe energies at 0K?
(3 things)

A
  • Minimum internal energy (u) at 0K
  • Ek = 0
  • Ep = minimum
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15
Q

Internal energy expressed as an equation?

A

Internal energy = Σ kinetic energy + potential energy

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16
Q

Symbol form of internal energy equation?

A

U = Σ Ek + Ep

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17
Q

Internal energy of an ideal gas equation?
(in data booklet)

A

U = 3/2 nRT

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18
Q

Why is the internal energy equation for an ideal gas different?
(2 things)

A
  • Ideal gas has no intermolecular forces
  • Therefore U = Σ Ek
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19
Q

What about the internal energy at 0K for an ideal gas?
(1 + 3-way)

A
  • No internal energy at 0k
  • U = Σ Ek and EK = 0
  • as Ek ∝ T
  • Therefore U = 0
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20
Q

What is thermodynamics?
(2-way)

A
  • The study of heat energy &
  • energy transfer
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21
Q

What is thermodynamics concerned with?
(3-way)
(probably optional)

A
  • Interactions within a system
  • and between the system
  • and its surroundings
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22
Q

If an object is hot, where would heat go?

A

To the cold surroundings

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23
Q

If the surroundings is hot and the object is cold, where would heat go?

A

To the cold object

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24
Q

When heat transfers, what eventually happens to both the object and surroundings?

A

Reach same temperature

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25
Q

When they reach the same temperature, what happens to heat transfer?

A

Net energy/heat transfer stops

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26
Q

The scientific term for net energy/heat transfer stopping?

A

Thermal equilibrium

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27
Q

Describe heat (systems)
(2-way + 2 things)

A
  • Heat = Q
  • is the energy flow from higher to lower temp.
  • Heat flows in/out of a system
  • System has energy not heat
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28
Q

Describe work (in systems)
(2 things + 2-way)

A
  • It’s like heat; energy in transit
  • System doesn’t have work
  • Has energy but work can be done by system
  • as it transfers energy
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29
Q

Can energy be created/destroyed?
…. Why bro?
(4 by 4 steps)

A

No:
- If gas has work done
- Has transferred energy
- Energy must’ve entered gas
- Heat flow into gas = increase in U + work done by gas

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30
Q

Work done by a gas in expanding/contracting expressed in words?

A

Change in work done = pressure x change in volume

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31
Q

Work done by a gas in expanding/contracting in symbol form?
(data booklet)

A

△W = p△V

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32
Q

Derivation of ΔW = pΔV?
(4-way)

A
  • Work = force x distance
  • W = F x Δx
  • W = P x A x Δx & A x Δx = ΔV
  • HENCE, ΔW = pΔV
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33
Q

What happens to heat if work is done on the system and △W is -ve?
(2 things)

A
  • Will flow out of system
  • IF not in isolation
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34
Q

If a constant force is applied, what happens to the pressure?
(△W = p△V)
(2 things)

A
  • Pressure = no change (isobaric)
  • △W proportional to volume
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35
Q

How to find work done from △W = p△V graph?

A

Area under graph

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36
Q

If the △W = p△V graph is curved, how to find work done?

A

Count squares to estimate area under curve

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37
Q

If volume increases & pressure remains constant, deduce about the change in temperature of the gas
(1 + 2-way)

A
  • PV/T is constant
  • At constant pressure
  • V & T increases
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38
Q

What would the △W = p△V graph look like if temperature was -ve?
(2 things)

A
  • Temp decreases = volume decreases
  • The opposite curve
39
Q

Explain work done by gas = expansion
(4 things)

A
  • Gas expanded…
  • Molecules lose KE
  • Positive work on piston
  • +ve△W
40
Q

Explain work done by system = compression
(4 things)

A
  • Gas compressed…
  • Molecules gain KE
  • Negative work on piston
  • -ve△W
41
Q

What is the first law of thermodynamics
(a word eqn)

A

Heat energy absorbed = increase in internal energy by system + work done by the system

42
Q

Symbol form of the first law of thermodynamics
(in data booklet)

A

Q = △U + W

43
Q

Define Q
(first law of thermodynamics)

A

Heat energy absorbed

44
Q

Define △U
(first law of thermodynamics)

A

Change in internal energy

45
Q

Define W
(first law of thermodynamics)

A

Work done by system

46
Q

What does it mean if Q is positive?
(first law of thermodynamics)
(2 things)

A
  • Heat enters system
  • Positive Q transfers energy to the system
47
Q

What does it mean if Q is negative?
(first law of thermodynamics)
(2 things)

A
  • Heat leaves system
  • Negative Q transfers energy from the system
48
Q

What does it mean if △U is positive?
(first law of thermodynamics)
(4-way)

A
  • Temperature increases
  • U ∝ T means an increase in T,
  • giving increase in U
  • U = positive
49
Q

What does it mean if △U is negative?
(first law of thermodynamics)
(1-3-way)

A
  • Temperature decreases
  • U ∝ T means a decrease in T,
  • giving a decrease in U
  • U = negative
50
Q

What does it mean if W is positive?
(first law of thermodynamics)
(5-way)

A
  • Work is done by the gas
  • Gas expanding
  • Positive change in volume
  • W = P x △V
  • W is positive
51
Q

What does it mean if W is negative?
(first law of thermodynamics)
(5-way)

A
  • Work is done on the gas
  • Gas compressing
  • Negative change in volume
  • W = P x -△V
  • W is negative
52
Q

How does a freezer use the first law of thermodynamics?
(Outside part)
(4 things)

A
  • Coolant/refrigerant put into pipes
  • Outside the freezer, pipes get thinner
  • gets pumped around pipes, compresses coolant
  • Coolant = warmer
53
Q

How does a freezer use the first law of thermodynamics?
(Inside part)
(3 things)

A
  • Coolant goes inside refrigerator
  • Pipes get wider
  • Coolant gets colder
54
Q

Explain freezer in terms of the 1st law of thermodynamics pt. 1
(Inside)
(4 things)

A
  • Pipe widens, volume increases
  • PV/T = constant (pressure constant)
  • Temp. inside pipe increases
  • Q = △U + W
55
Q

Explain freezer in terms of the 1st law of thermodynamics pt. 2
(Inside)
(3 things)

A
  • W positive (expanded), △U positive (inc. in T)
  • Q must be positive
  • Heat flows from freezer into pipe
56
Q

What about freezer outside in terms of the 1st law of thermodynamics?
(Independence right here… actually major check up yet no nothing soooo…)

57
Q

1st law of thermodynamics data booklet edition?

A

△U = Q - W
(pray u know by then)

58
Q

Sub △W = p△V into the 1st law of thermodynamics
(That’s work done in expanding a system)
(2-way)

A
  • Q = △U + W
  • Q = △U + P△V
59
Q

What are the 4 different processes that affect how we write the 1st law of thermodynamics?

A
  • Adiabatic processes (Q = 0)
  • Constant Volumes processes (W = 0)
  • Constant temperature (△U = 0)
  • Cyclical process (W = Q)
60
Q

What is the adiabatic processes?
(Q = 0)

A

When P, V & T not fixed

61
Q

Explain adiabatic processes?
(2-way)

A
  • If system well insulated
  • No transfer of heat in/out of system
62
Q

What does the first law become in adiabatic processes?
(2 way)

A

△U = W
(nR△T = area under graph)

63
Q

Explain the graph of adiabatic processes?
(4 things)
(Whiteboard, means u draw it)

A
  • Diagonal down line
  • Going up = compression (-ve work)
  • Going down = expansion (+ve work)
  • PV/T = constant
64
Q

What is constant volume processes?
(W = 0)

A

Isochoric
(V = fixed)

65
Q

Explain constant volume processes?
(4 things)

A
  • If volume held constant
  • System can’t do work
  • Happens to a solid/liquid
  • due to volume being fixed
66
Q

What does the first law become in constant volume processes?
(3 way….?)

A

△U = Q
(3/2 n R△T = △U)
(W = P△V, SO W = 0)

67
Q

Explain the graph of constant volume processes?
(3 things)
(Whiteboard, means u draw it)

A
  • Straight line down/up
  • No area under graph, no work
  • △pV = nR△T
68
Q

What is “constant temperature”?
(△U = 0)

A

Isothermal
(T = fixed)

69
Q

Explain “constant temperature”?
(2-way)

A
  • For an isothermal process
  • pV = constant
70
Q

What does the first law become in “constant temperature”?
(3 way…?)

A

△U = 0
U ∝ T
Q = W

71
Q

Explain the graph of “constant temperature”?
(3 things)
(Whiteboard, means u draw it)

A
  • Curving down line
  • PV = constant
  • Work = area under graph
72
Q

What is cyclical process?
(W = Q)

A

Work done = heat flow

73
Q

Explain cyclical process?
(3 things)

A
  • After certain interchanges of heat and work,
  • are restored to their initial state
  • So, no properties of the system are changed
74
Q

What does the first law become in cyclical process?

75
Q

Explain the graph of cyclical process?
(4 things)
(Whiteboard, means u draw it)

A
  • Triangle with points A, B & C
  • Area of triangle = total work done
  • W +’ve if expansion higher
  • W -‘ve if compression higher
76
Q

How much energy required to raise temperature of 1kg of a substance?

77
Q

“Specific heat capacity” equation
(different re-iteration in data booklet)

A

E = m x c x △T

78
Q

Word form of “specific heat capacity” equation?

A

Energy = mass x specific heat capacity x rise in temperature

79
Q

Specific heat capacity at it’s “base”?
(2-way-step)

A
  1. C = J/KgK
  2. JKg-1K-1
80
Q

Specific heat capacity at it’s SI units?
(Another 2-way-step)

A
  1. C = Kgm2s-2/KgK
  2. m2s-2k-1
81
Q

How do u find the thermal equilibrium temperature during energy transfer between 2 blocks?
(5 steps)
(Heavily question in-need, refer to “page 19”)
(Whiteboard)

A
  1. Use E = m x c x △T
  2. Find their value for each block
  3. For T of each, ? - T if higher temp, vice versa for other
  4. Left = Right
  5. Re-arrange, VOILA
82
Q

What are the items needed for the practical to finding the specific heat capacity?
(7 things)

A
  • Power supply
  • Ammeter
  • Voltmeter
  • Thermometer
  • Heater
  • Metal block
  • “insulation”
83
Q

How do u place the ammeter and voltmeter in the practical to finding the specific heat capacity?
(2-way)

A
  • Ammeter = series
  • Voltmeter = parallel
84
Q

How do u draw the diagram of the practical to work out the specific heat capacity?
(Whiteboard lol)

A

Trust on the following day

85
Q

Method for practical to work out specific heat capacity?
(3 steps)

A
  1. Record start temperature
  2. Turn heater on (record I, V) for 10 mins
  3. Record highest temperature reached
86
Q

How do u calculate the energy?
(Practical to find specific heat capacity)

A

E = IVt
Energy = current x voltage x time

87
Q

Some energy will be lost to the material of the container. How it’ll affect experimental value + how to minimise that?
(Practical to find specific heat capacity)
(2-way y’all)

A
  1. Experimental value = higher than actual value
  2. Insulation to minimise effect
88
Q

Units for specific heat capacity. How come u can leave the temperature at degrees Celsius?
(Practical to find specific heat capacity)
(3 thingies)

A
  • Formula for SHC uses difference in temperature
  • NOT absolute temperature
  • and 1°c = 1K
89
Q

How to improve results and experiment?
(Practical to find specific heat capacity)
(3… way)

A
  • Add more insulation, by adding lid, prevent heat loss to surroundings
  • Add oil, induce contact with heat & block
  • Do repeats to check for anomalies
90
Q

The main way to improve investigation to measure specific heat capacity?
(2 things)
(probably white board??????)

A
  • Range of results taken
  • Graph analysis used
91
Q

This booklet contains the min + max gradients, therefore, pls don’t forget (hopefully) that for the Uncertainties (EXCLUSIVE)

92
Q

Ya did it

A

Always check

93
Q

Spam the questions

The final mock (Physics) (7 decks)

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