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OCR A Physics A Level > 5.1 Thermal Physics > Flashcards

5.1 Thermal Physics Flashcards

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1
Q

Thermal Equilibrium

A

A higher temperature object in contact with a low temperature object will transfer heat from the high temperature to the lower one. The rate of change of temperature will decrease as the objects near each others temperatures, eventually they will effectively be at the same temperature.

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2
Q

Features of the absolute scale of temperature (2)

A
  • Starts at absolute zero

- Not dependent on any physical property of matter

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3
Q

Thermodynamic Scale

A

Another name for absolute scale

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4
Q

How change in Celsius relates to change in kelvin

A

They are 1 to 1

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5
Q

Spacing of particles in a solid

A

Close together (high density)

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6
Q

Spacing of particles in a liquid

A

Close together (high density)

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7
Q

Spacing of particles in a gas

A

Sparse (low density)

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8
Q

Motion of particles in a solid

A

Vibrate around a fixed equilibrium positions but have relatively small motion compared to liquid and gas

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9
Q

Motion of particles in a liquid

A

Can move past each other but are still attracted

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10
Q

Motion of particles in a gas

A

Move mostly freely. Almost all kinetic energy is translational (in the form of linear motion)

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11
Q

Kinetic model

A

Solids, liquids and gases are made up of small moving or vibrating particles

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12
Q

Brownian motion

A

The random movement of particles

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13
Q

Example of Brownian motion

A

Observing smoke particles with a bright light and a microscope. They show Brownian motion.

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14
Q

Internal energy

A

The sum of the randomly distributed kinetic and potential energies of all the atoms and molecules in a system

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15
Q

Feature of 0K in a system

A

Minimal internal energy

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16
Q

How is internal energy effected by an increase in temperature

A

increased

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17
Q

Temperature of a substance that is changing state

A

constant

18
Q

A substance is heated and begins to melt. What is happening to it’s internal energy as it melts

A

It increases. (The kinetic energy stays the same but the potential energy increases)

19
Q

Maxwell-Boltzmann distribution

A

Graph of number of molecules against speed. Looks kinda similar to a normal distribution with the right side tailing

20
Q

Specific heat capacity

A

The energy required to raise 1kg of a material by 1K

21
Q

Experiment for specific heat capacity

A

Put the material in an insulator. Heat the material with an electric heater, recording the current and voltage with an ammeter and voltmeter. Record temperature with a thermometer. Once the temperature has changed by 10K calculate the total energy that went in by E = IVt and then calculate c.

22
Q

Specific latent heat

A

Energy required to change the state of 1kg of a material

23
Q

Name for specific latent heat solid->liquid

A

fusion

24
Q

Name for specific latent heat liquid->gas

A

Vaporisation

25
Q

Equation for specific heat capacity

A

E = mc(delta t)

26
Q

Equation for specific latent heat

A

E = mL

27
Q

Experiment for specific latent heat of fusion

A

Fill two funnels with the same mass of ice. Heat one of them with a heater of known power. After 10 minutes compare the amount of water that has dripped out of each one and calculate the difference in mass. Sub into E = mL to get L,

28
Q

Experiment for specific latent heat of vaporisation

A

Heat liquid to boiling point in a distilling flask. Condense the vapour given off and then divide the energy put in by the mass of the vapour. (For more accuaracy do this twice with different powers on the heater and then subtract one from the other in order to eliminate heat lost to surroundings)

29
Q

Model of kinetic theory of gases

A

Models a gas as a large number of small particles that are in constant motion and behave as an ideal gas

30
Q

Assumptions for an ideal gas (6)

A
  • Large number of particles
  • Particles move rapidly and randomly
  • All collisions are perfectly elastic
  • Negligible forces between particles except during collision
  • Time for collision to happen is negligible compared to the time between collisions
  • Particles have negligible volume compared to that of the container
31
Q

When a real gas behaves like an ideal gas

A

Low pressure and high temperature

32
Q

Pressure as a result of a gas

A

The movement of the individual particles in a gas causes them to collide with the container walls and exerting a force on the walls

33
Q

Ideal gas equation

A 
pV = nRT
p - pressure
V - volume
n - number of moles
R - molar gas constant
T - Temperature (kelvin)
34
Q

Boyles law

A

Pressure is proportional to 1/Volume

35
Q

Experiment to investigate Boyles law

A

Fill a transparent tube with oil. Attach a valve, pressure gauge, scale and pump. Pump air into the system up to a high pressure. Then release a small amount of air and note the pressure from the gauge and the volume from

36
Q

Experiment to determine absolute zero

A

Fill a flask with a fixed mass of gas and attach a pressure gauge to the flask. Submerge the flask into water of varying temperature and record the pressure and temperature in each case. Plot a graph of pressure against temperature and it should be a straight line. Continuing the straight line on into the negative celsius it would cross the x axis at absolute zero.

37
Q

Experiment to determine absolute zero

A

Fill a flask with a fixed mass of gas and attach a pressure gauge to the flask. Submerge the flask into water of varying temperature and record the pressure and temperature in each case. Plot a graph of pressure against temperature and it should be a straight line. Continuing the straight line on into the negative celsius it would cross the x axis at absolute zero.

38
Q

Boltzmann constant

A

R/(NA)

Molar gas constant / Avogadro constant

39
Q

How to calculate internal energy of an ideal gas

A

Using the equation for energy of a single particle (E=1.5kT). Multiply by the number of particles

40
Q

Internal energy of an ideal gas

A

Equal to the total random kinetic energy (ideal gas has no potential energy)

OCR A Physics A Level (10 decks)

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