Unit 3.4 Thermal Physics Flashcards by Shirou Aizen

What is internal energy?
(3 things)

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

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

Energy a substance has
due to the movement of the ptcls in it

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

Energy a substance contains
due to the breaking of bonds
& overcoming molecular attractive forces

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

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

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

A - B = rise
B - C = constant
C - D = rise
D - E = constant
E - F = rise

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

KE remains constant
PE increasing as
intermolecular forces are overcome

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

None
KE increases as temp. increase
PE increases as ptcls move further apart

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Which letters does only PE increase?
(3 things)

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

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

A - B
C - D
E - F

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State the relationship between temperature and KE?

Directly proportional
(E_k ∝ T)

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

Bonds breaking
Particles no longer fixed in place
Can move around each other

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

All bonds broken
Particles are completely free

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

Particles at the surface of the substance
break all bonds and become free

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

Minimum internal energy (u) at 0K
E_k = 0
E_p = minimum

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Internal energy expressed as an equation?

Internal energy = Σ kinetic energy + potential energy

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Symbol form of internal energy equation?

U = Σ E_k + E_p

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

U = 3/2 nRT

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

Ideal gas has no intermolecular forces
Therefore U = Σ E_k

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

No internal energy at 0k
U = Σ E_k and E_K = 0
as E_k ∝ T
Therefore U = 0

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What is thermodynamics?
(2-way)

The study of heat energy &
energy transfer

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

Interactions within a system
and between the system
and its surroundings

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If an object is hot, where would heat go?

To the cold surroundings

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

To the cold object

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

Reach same temperature

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

Net energy/heat transfer stops

The scientific term for net energy/heat transfer stopping?

Thermal equilibrium

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

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

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

- 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

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

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

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

Change in work done = pressure x change in volume

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

△W = p△V

Derivation of ΔW = pΔV? (4-way)

- Work = force x distance - W = F x Δx - W = P x A x Δx **&** A x Δx = ΔV - HENCE, ΔW = pΔV

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

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

- Pressure = no change (isobaric) - △W proportional to volume

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

Area under graph

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

Count squares to estimate area under curve

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

- PV/T is constant - At constant pressure - V & T increases

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

- Temp decreases = volume decreases - The opposite curve

Explain work done by gas = expansion (4 things)

- Gas expanded... - Molecules lose KE - Positive work on piston - +ve△W

Explain work done by system = compression (4 things)

- Gas compressed... - Molecules gain KE - Negative work on piston * -ve△W

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

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

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

Q = △U + W

Define Q (first law of thermodynamics)

Heat energy absorbed

Define △U (first law of thermodynamics)

Change in internal energy

Define W (first law of thermodynamics)

Work done by system

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

- Heat enters system - Positive Q transfers energy to the system

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

- Heat leaves system - Negative Q transfers energy from the system

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

- Temperature increases - U ∝ T means an increase in T, - giving increase in U - U = positive

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

- Temperature decreases - U ∝ T means a decrease in T, - giving a decrease in U - U = negative

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

- Work is done by the gas - Gas expanding - Positive change in volume - W = P x △V - W is positive

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

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

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

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

- Coolant goes inside refrigerator - Pipes get wider - Coolant gets colder

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

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

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

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

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

Uhhh

1^st law of thermodynamics data booklet edition?

△U = Q - W (pray u know by then)

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

- Q = △U + W - Q = △U + P△V

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

- Adiabatic processes (Q = 0) - Constant Volumes processes (W = 0) - Constant temperature (△U = 0) - Cyclical process (W = Q)

What is the adiabatic processes? (Q = 0)

When P, V & T not fixed

Explain adiabatic processes? (2-way)

- If system well insulated - No transfer of heat in/out of system

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

△U = W (nR△T = area under graph)

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

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

What is constant volume processes? (W = 0)

Isochoric (V = fixed)

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

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)

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

- Straight line down/up - No area under graph, no work - △pV = nR△T

What is "constant temperature"? (△U = 0)

Isothermal (T = fixed)

Explain "constant temperature"? (2-way)

- For an isothermal process - pV = constant

What does the first law become in "constant temperature"? (3 way...?)

△U = 0 U ∝ T Q = W

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

- Curving down line - PV = constant - Work = area under graph

What is cyclical process? (W = Q)

Work done = heat flow

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

What does the first law become in cyclical process?

△U = 0

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

- Triangle with points A, B & C - Area of triangle = total work done - W +'ve if expansion higher * W -'ve if compression higher

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

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

E = m x c x △T

Word form of "specific heat capacity" equation?

Energy = mass x specific heat capacity x rise in temperature

Specific heat capacity at it's "base"? (2-way-step)

1. C = J/KgK 2. JKg^-1K^-1

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

1. C = Kgm²s^-2/KgK 2. m²s^-2k^-1

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)

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

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"

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

- Ammeter = series - Voltmeter = parallel

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

Trust on the following day

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

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

E = IVt Energy = current x voltage x time

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

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

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**

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

- Range of results taken - Graph analysis used

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

Hope

Ya did it

Always check

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