Thermal Physics Flashcards

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1
Q

Define Heat

A

The energy transferred between two objects because of the temperature difference between them.

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2
Q

Two objects are in thermal equilibrium if

A

No net flow of heat in thermal contact

At the same temp

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3
Q

Define absolute zero

A

Zero point on thermodynamic temperature scale in kelvin

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4
Q

Thermometric properties are

A

The properties of a thermometer that allows it to measure temperature

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5
Q

Triple point of water

A

273.16K/0.01C

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6
Q

Define ideal gas

A

An ideal gas is a gas which obeys the equation pV = nRT, where
p is the pressure of the gas,
V is the volume of the gas,
T is the thermodynamic temperature of the gas,
and N is the amount of gas in moles.

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7
Q

Pressure law

A

Pressure is proportionate to volume

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8
Q

Charles law

A

Volume is proportionate to temperature

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9
Q

Boyle’s law

A

Pressure is inversely proportional to temperature

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10
Q

6 assumptions of the kinetic theory of gases

A
  1. Any gas is made up of a large no. of particles
  2. Constant and random motion
  3. Perfectly elastic collisions between particles and wall
  4. Vol is negligible, any 2 particles are far apart, low chance of collision
  5. Force between particles is negligible except during time of collision
  6. Duration of collision is negligible
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11
Q

Define Heat capacity

A

Quantity of heat required to raise the body temp by 1 degree

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12
Q

Define specific heat capacity

A

Quantity of heat required to raise the temp of a unit mass of the substance by 1 kelvin

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13
Q

Formula for specific heat capacity

A

Q = mc(change in temp)

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14
Q

Specific latent heat of fusion

A

Quantity of heat required to convert a unit mass of solid to liquid without any change in temperature

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15
Q

Specific latent heat of vaporization

A

Quantity of heat required to convert a unit mass of liquid to gas without any change in temperature

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16
Q

Define one kelvin

A

1/273.16 of the thermodynamics temp of the triple point of water

17
Q

Internal energy of a system is

A

The sum of the random distribution of microscopic kinetic energy and microscopic potential energy of all the atoms on molecules

18
Q

The first law of thermodynamics states that

A

The INCREASE in internal energy of a system is equal to the sum of the thermal energy added to it and the work done to the system.

Change in U = Q + WD

19
Q

Isothermal

A

Temp is constant. ∆U = 0, Q = -W

20
Q

Isochloric/Isovolumetric

A

Volume is constant. ∆U = Q, W = 0

21
Q

Isobaric

A

Pressure is constant. W = -p∆V, ∆U = area under graph

22
Q

Adiabatic

A

No heat gain or loss throughout. Q = 0, ∆U = W

23
Q

Cyclic

A

No net change of thermal energy. ∆U = 0

24
Q

What affects a change in microscopic kinetic energy?

A

Temperature

25
Q

What affects a change in microscopic potential energy?

A

State of body

26
Q

By reference to the energy of molecules, explain why the internal energy of an ideal gas is proportional to its thermodynamic temperature.

A

internal energy definition

For an ideal gas, the microscopic PE of the molecules is negligible because there are no intermolecular forces,

hence internal energy of an ideal gas is solely due to the microscopic KE of the gas molecules.

Since microscopic KE is proportional to thermodynamic temperature, internal energy of an ideal gas would be proportional to its thermodynamic temperature.

27
Q

Why is the specific heat capacity larger when heating takes place at constant pressure rather than at constant volume?

A

To raise the temperature of a unit mass of neon gas by 1K, the increase in internal energy Δ *U would be the same.

By the 1st law of thermodynamics ΔU = Q + W , for a constant pressure process, work is done by the gas as it expands during heating, so thermal energy required will be the sum of the increase in internal energy and work done by the gas (Q = Δ*U + W)

For a constant volume process, no work is done so thermal energy required is only to increase internal energy (Q = Δ*U)

Since for constant pressure process, more thermal energy is required for the same rise in temperature ΔT , by Q = mcΔT, c would be larger.

28
Q

Derive kinetic theory equation

A

Δp = -mcx - mcx = -2mcx

f = cx/2L

Δp/Δt = cx/2L(-2mcx) = -mcx²/L

Force exerted by wall on particle = -mcx²/L

Force exerted by particle on wall = mcx²/L

(mcx²/L)/L² = mcx²/L³ = mN<cx>²/L³ = mN/L³ (⅓c) = ⅓(Nm/V)<cx>² _</cx></cx>

PV = ⅓(Nm)<cx>² _</cx>

29
Q

Derive KE of an ideal gas particle

A

⅓(Nm)<c>² = NkT
(Nm)<c>² = 3NkT
½m<c>² = 3/2 NkT = U_</c></c></c>

30
Q

Define the internal energy of an ideal gas.

A

The sum of the random microscopic kinetic energy of all the gas molecules only, since there is no microscopic potential energy for an ideal gas because there are no intermolecular forces of attraction.