Unit 3.4 Thermal Physics Flashcards
(92 cards)
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)
2
Q
What is KE in a substance?
(2-way)
A
- Energy a substance has
- due to the movement of the pctls in it
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
4
Q
Tell me about the changes of state
(4 things)
A
- As temp of a substance rises
- changes state
- Internal energy also rises
- BUT, KE & PE don’t rise simultaneously
5
Q
Describe the heating curve from points A - F
(5 points to describe)
A
- A - B = rise
- B - C = constant
- C - D = rise
- D - E = constant
- E - F = rise
6
Q
From the heating curve, why does the temp. remain constant at some points?
(3 things)
A
- KE remains constant
- PE increasing as
- intermolecular forces are overcome
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
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
9
Q
From the heating curve, which points have both KE & PE increasing?
(3 things)
A
- A - B
- C - D
- E - F
10
Q
State the relationship between temperature and KE?
A
Directly proportional
(Ek ∝ T)
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
12
Q
Describe the process of boiling using simple kinetic model
(2 things)
A
- All bonds broken
- Particles are completely free
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
14
Q
From heating curve, describe energies at 0K?
(3 things)
A
- Minimum internal energy (u) at 0K
- Ek = 0
- Ep = minimum
15
Q
Internal energy expressed as an equation?
A
Internal energy = Σ kinetic energy + potential energy
16
Q
Symbol form of internal energy equation?
A
U = Σ Ek = Ep
17
Q
Internal energy of an ideal gas equation?
(in data booklet)
A
U = 3/2 nRT
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
19
Q
What about the internal energy at 0K for an ideal gas?
(4 things)
A
- No internal energy at 0k
- U = Σ Ek and EK = 0
- as Ek ∝ T
- Therefore U = 0
20
Q
What is thermodynamics?
A
The study of heat energy and energy transfer
21
Q
What is thermodynamics concerned with?
(3 things)
(probably optional)
A
- Interactions within a system
- and between the system
- and its surroundings
22
Q
If an object is hot, where would heat go?
A
To the cold surroundings
23
Q
If the surroundings is hot and the object is cold, where would heat go?
A
To the cold object
24
Q
When heat transfers, what eventually happens to both the object and surroundings?
A
Reach same temperature
25
When they reach the same temperature, what happens to heat transfer?
Net energy/heat transfer stops
26
The scientific term for net energy/heat transfer stopping?
Thermal equilibrium
27
Describe heat (systems)
(4 things)
- Heat = Q
- is the energy flow from higher to lower temp.
- Heat flows in/out of a system
- System has energy **not** heat
28
Describe work (systems)
(5 things)
- It's like heat
- It's energy in transit
- System **doesn't** have work
- Has energy but work can be done by system
- as it transfers energy
29
Can energy be created/destroyed?
No.
30
What does it mean if gas has done work?
(2 things)
- It has transferred energy
- Energy entered the gas
31
Heat flow into gas = ?
(2 things)
- Increase in internal energy
- Work done by gas
32
Work done by a gas in expanding/contracting expressed in words?
Change in work done = pressure x change in volume
33
Work done by a gas in expanding/contracting in symbol form?
(data booklet)
△W = p△V
34
What happens to heat if work is done on the system and △W is -ve?
(2 things)
- Will flow out of system
- IF not in isolation
35
If a constant force is applied, what happens to the pressure?
(△W = p△V)
- Pressure = no change (isobaric)
- △W proportional to volume
36
How to find work done from △W = p△V graph?
Area under graph
37
If the △W = p△V graph is curved, how to find work done?
Count squares to estimate area under curve
38
If volume increases & pressure remains constant, deduce about the change in temperature of the gas
(3 things)
- PV/T is constant
- At constant pressure
- V & T increases
39
What would the △W = p△V graph look like if temperature was -ve?
- Temp decreases = volume decreases
- The opposite curve
40
Explain work done by gas = expansion
(4 things)
- Gas expanded
- Molecules lose KE
- Positive work on piston
- +ve△W
41
Explain work done by system = compression
(4 things)
- Gas compressed
- Molecules gain KE
- Negative work on piston
* -ve△W
42
What is the first law of thermodynamics
Heat energy absorbed = increase in internal energy by system + work done by the system
43
Symbol form of the first law of thermodynamics
(in data booklet)
Q = △U + W
44
Define Q
(first law of thermodynamics)
Heat energy absorbed
45
Define △U
(first law of thermodynamics)
Increase in internal energy
46
Define W
(first law of thermodynamics)
Work done by system
47
What does it mean if Q is positive?
(first law of thermodynamics)
(2 things)
- Heat enters system
- Positive Q transfers energy to the system
48
What does it mean if Q is negative?
(first law of thermodynamics)
(2 things)
- Heat leaves system
- Negative Q transfers energy from the system
49
What does it mean if △U is positive?
(first law of thermodynamics)
(4 things)
- Temperature increases
- U ∝ T means an increase in T,
- giving increase in U
- U = positive
50
What does it mean if △U is negative?
(first law of thermodynamics)
(4 things)
- Temperature decreases
- U ∝ T means a decrease in T,
- giving a decrease in U
- U = negative
51
What does it mean if W is positive?
(first law of thermodynamics)
(5 things)
- Work is done by the gas
- Gas expanding
- Positive change in volume
- W = P x △V
- W is positive
52
What does it mean if W is negative?
(first law of thermodynamics)
(5 things)
- Work is done on the gas
- Gas compressing
- Negative change in volume
- W = P x -△V
- W is negative
53
How does a freezer use the first law of thermodynamics?
(Outside part)
(4 things)
- Coolant/refrigerant put into pipes
- Outside the freezer, pipes get thinner
- gets pumped around pipes, compresses coolant
- Coolant = warmer
54
How does a freezer use the first law of thermodynamics?
(Inside part)
(3 things)
- Coolant goes inside refrigerator
- Pipes get wider
- Coolant gets colder
55
Explain freezer in terms of the 1st law of thermodynamics
(Inside)
(7 things)
- Pipe widens, volume increases
- PV/T = constant (pressure constant)
- Temp. inside pipe increases
- Q = △U + W
- W positive (expanded), △U positive (inc. in T)
- Q must be positive
- Heat flows from freezer into pipe
56
What about freezer outside in terms of the 1st law of thermodynamics?
(Independence right here)
Uhhh
57
1st law of thermodynamics data booklet edition?
△U = Q - W
(pray u know by then)
58
Sub △W = p△V into the 1st law of thermodynamics
(That's work done in expanding a system)
(2-way)
- Q = △U + W
- Q = △U + P△V
59
What are the 4 different processes that affect how we write the 1st law of thermodynamics?
- Adiabatic processes (Q = 0)
- Constant Volumes processes (W = 0)
- Constant temperature (△U = 0)
- Cyclical process (W = Q)
60
What is the adiabatic processes?
(Q = 0)
When P, V & T not fixed
61
Explain adiabatic processes?
(2-way)
- If system well insulated
- No transfer of heat in/out of system
62
What does the first law become in adiabatic processes?
(2 way)
△U = W
(nR△T = area under graph)
63
Explain the graph of adiabatic processes?
(4 things)
- Diagonal down line
- Going up = compression (-ve work)
- Going down = expansion (+ve work)
- PV/T = constant
64
What is constant volume processes?
(W = 0)
Isochoric
(V = fixed)
65
Explain constant volume processes?
(4 things)
- If volume held constant
- System can't do work
- **Happens to a solid/liquid**
- due to volume being fixed
66
What does the first law become in constant volume processes?
(3 way....?)
△U = Q
(3/2 n R△T = △U)
(W = P△V, SO W = 0)
67
Explain the graph of constant volume processes?
- Straight line down/up
- No area under graph, no work
- △pV = nR△T
68
What is "constant temperature"?
(△U = 0)
Isothermal
(T = fixed)
69
Explain "constant temperature"?
(2-way)
- For an isothermal process
- pV = constant
70
What does the first law become in "constant temperature"?
(3 way...?)
△U = 0
U ∝ T
Q = W
71
Explain the graph of "constant temperature"?
(3 things)
- Curving down line
- PV = constant
- Work = area under graph
72
What is cyclical process?
(W = Q)
Work done = heat flow
73
Explain cyclical process?
(3 things)
- After certain interchanges of heat and work,
- are restored to their initial state
- So, no properties of the system are changed
74
What does the first law become in cyclical process?
△U = 0
75
Explain the graph of cyclical process?
(4 things)
- Triangle with points A, B & C
- Area of triangle = total work done
- W +'ve if expansion higher
* W -'ve if compression higher
76
How much energy required to raise temperature of 1kg of a substance?
1K
77
"Specific heat capacity" equation
(different re-iteration in data booklet)
E = m x c x △T
78
Word form of "specific heat capacity" equation?
Energy = mass x specific heat capacity x rise in temperature
79
Specific heat capacity at it's "base"?
(2-way-step)
1. C = J/KgK
2. JKg-1K-1
80
Specific heat capacity at it's SI units?
1. C = Kgm2s-2/KgK
2. m2s-2k-1
81
How do u find the thermal equilibrium temperature during energy transfer between 2 blocks?
(5 steps)
(Heavily question in-need)
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
What are the items needed for the practical to finding the specific heat capacity?
(7 things)
- Power supply
- Ammeter
- Voltmeter
- Thermometer
- Heater
- Metal block
- "insulation"
83
How do u place the ammeter and voltmeter in the practical to finding the specific heat capacity?
(2-way)
- Ammeter = series
- Voltmeter = parallel
84
How do u draw the diagram of the practical to work out the specific heat capacity?
Trust on the following day
85
Method for practical to work out specific heat capacity?
(3 steps)
1. Record start temperature
2. Turn heater on (record I, V) for 10 mins
3. Record highest temperature reached
86
How do u calculate the energy?
(Practical to find specific heat capacity)
E = IVt
Energy = current x voltage x time
87
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)
1. Experimental value = higher than actual value
2. Insulation to minimise effect
88
Units for specific heat capacity. How come u can leave the temperature at degrees Celsius?
(Practical to find specific heat capacity)
(3 thingies)
- Formula for SHC uses difference in temperature
- NOT absolute temperature
- and 1°c = 1K
89
How to improve results and experiment?
(Practical to find specific heat capacity)
(3... way)
- 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
The main way to improve investigation to measure specific heat capacity?
(2 things)
(probably white board)
- Range of results taken
- Graph analysis used
91
Ya did it
Always check
92
Spam the questions
K
