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Physics 2 > Thermal Physics > Flashcards

Thermal Physics Flashcards

1
Q

What are the three laws of thermodynamics?

A

Zeroth law, Frist law, Second law

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2
Q

What is Zeroth law?

A

If A and B are in thermal equilibrium with C then A and B are in thermal equilibrium with each other

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3
Q

What is First law?

A

ΔE=Q-W (ΔE is net change in total energy, Q is heat added to the system, W is work doen by the system)

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4
Q

What is Second law?

A

In all spontaneous processes, the entropy of the universe increases i.e. entropy always increases with time

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5
Q

What is entropy?

A

The degree of disorder or randomness in a system

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6
Q

What is a system?

A

A portion of the Universe with certain measurable
quantities (such as pressure or volume) which determine the equilibrium state of
the system

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7
Q

What is an isolated system?

A

A system that does not interact with its surroundings by exchanging heat
energy, mechanical energy or material

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8
Q

What is a closed system?

A

A system in which energy but not material can be exchanged

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9
Q

What is am adiabatic wall?

A

The system is thermally isolated and

only mechanical energy (not heat) can be exchanged with the surroundings (e.g. a vacuum flask)

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10
Q

What is a diathermal wall?

A

Heat exchange is permitted; systems

connected by a diathermal wall are in thermal contact (e.g. a metal wall)

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11
Q

What does equilibrium mean?

A

All bulk physical properties are uniform throughout the system, they are time-independent

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12
Q

What does macroscopic mean?

A

Large-scale or bulk properties of a gas (e.g.: P, V, T)

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13
Q

What does microscopic mean?

A

Properties on the atomic-level (e.g.: vrms, vmp.)

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14
Q

What are state variables?

A

These define the state of a system

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15
Q

What does intensive mean?

A

Independent of the size of the system

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16
Q

Give 2 examples of intensive properties

A

pressure, tension

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17
Q

What does extensive mean?

A

Proportional to the size of the system

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18
Q

Give 2 examples of extensive properties

A

volume or length

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19
Q

What are equilibrium states of thermodynamic systems determined by?

A

Suitable pairs of conjugate variables

20
Q

What is a pair of conjugate variables?

A

One variable will be intensive and the other extensive

21
Q

Give an example of pairs of conjugate variables for a gas and for a stretched wire

A

(P, V) for a gas. Or

(tension, length) for a stretched wire

22
Q

What dimensions does the product of all conjugate pairs have?

A

The dimentions of energy

23
Q

What is a function of state?

A

Any quantity which takes a unique value for each equilibrium state of a system

24
Q

Give an example of a state funtion

A

Internal energy U or entropy S

25
Q

What do functions of state depend on?

A

Only on the state itself and not on how that state was

produced

26
Q

Why is heat not a function of state?

A

Because it is associated with a transfer of energy between states

27
Q

What is heat (Q)?

A

The form of energy transferred between substances due to temperature differences between them

28
Q

What happens in terms of heat when two objects are NOT in thermal equilibrium?

A

Heat flows from the hotter object to the colder object until thermal equilibrium is reached

29
Q

What is temperature?

A

The property which determines whether or not a system is in thermal equilibrium with other systems

30
Q

What are is the condition for Thermal equilibrium?

A

same temperature

31
Q

What is the condition for Mechanical equilibrium?

A

no unbalanced forces acting

32
Q

What is the condition for Chemical equilibrium?

A

no chemical reactions occurring

33
Q

What do Non-uniformities in a system result in?

A

a gradient and, hence, momentum, heat

and / or matter flows until thermodynamic equilibrium is reached

34
Q

What are Consequences of Thermodynamic Equilibrium On a macroscopic level?

A

variables have constant values in time and space (i.e.:

throughout the system)

35
Q

What are Consequences of Thermodynamic Equilibrium On a microscopic level?

A 
any process (e.g.: diffusion, collisions) must have an
equal probability of going in the opposite direction
36
Q

What is the equation of state?

A

f(P, V, T) = 0

37
Q

What is an ideal gas?

A

A gas for which hydrostatic equilibrium holds. i.e.: the inward force of gravity balances the outward gas pressure

38
Q

What do we assume in an ideal gas?

A

that atoms or molecules are non-interacting and

point-like

39
Q

What is the equation of state with R = 8.31 J K^–1 mol^–1?

A

f(P, V, T) = PV – nRT = 0

40
Q

How would we write the equation of state with the boltzmann constant?

A

PV – nkBT = 0

41
Q

What is a non-ideal gas?

A

A gas which has molecules with a finite volume and as a consequence, intermolecular forces (which are attractive) must be considered

42
Q

What is The equation of state for a van der Waals gas?

A

f(P, V, T) = (P+(n^2a/V^2))(V-nB)-nRT=0

43
Q

What is An indicator diagram?

A

a graph of an intensive variable (e.g.: P) against its conjugate extensive variable (e.g.: V)

44
Q

What is an isotherm?

A

The continuous line between any two states (P, V) and (P’,V’) in thermal equilibrium with each other (they will beat the same temperature)

45
Q

Describe Isotherms for a van der Waals gas (3)

A 
1. The isotherms look the same for both
gas types at high temperatures
2. The behaviour begins to change as
temperatures drop
3. Below a critical temperature Tc a phase
change occurs

Physics 2 (5 decks)

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