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AQA A Level Physics(Option A: Astrophysics) > Thermal Physics > Flashcards

Thermal Physics Flashcards

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1
Q

Define absolute zero

A

The lowest possible temperature a substance can have, where there is no particle movement. -273°C or 0K

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2
Q

State the conversion equation from degrees Celsius to kelvins

A

K = C + 273

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3
Q

What happens to a particle’s average speed, average kinetic energy and distribution curve as temperature increases?

A
  • As temperature increases, average particle speed increases
  • As temperature increases, average particle kinetic energy increases
  • The distribution curve is more spread out
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4
Q

Why is average speed and kinetic energy used for particles in a gas?

A

As the particles in a gas don’t all travel at the same speed

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5
Q

What is internal energy?

A

The sum of kinetic and potential energies of all a body’s randomly distributed particles

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6
Q

When do gases not have potential energy?

A

When the gas is an ideal gas

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7
Q

How can the internal energy of a system be increases?

A
  • By heating the system
  • By doing work to transfer energy to the sytem, i.e changing shape
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8
Q

In what direction is heat transfer?

A
  • From hotter substances to colder substances
  • The higher the difference in temperature between the substances, the faster the heat transfer
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9
Q

Define specific heat capacity

A

The amount of energy needed to raise the temperature of 1kg of the substance by 1K

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10
Q

When a substance changes state, what happens to its internal energy, kinetic energy, and temperature?

A
  • Internal energy changes as potential energy of particles is altered
  • Kinetic energy stays the same
  • Temperature stays the same
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11
Q

Describe the graph of temperature against internal energy for a sample of water

A
  • Constant gradient until 100°C as particles gain kinetic energy as water is heated
  • Horizontal line as kinetic energy stays same while potential energy increases to break bonds
  • Constant gradient past 100°C once water becomes vapour
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12
Q

Define specific latent heat

A

The amount of energy needed to change the state of 1kg of a substance

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13
Q

State Boyle’s Law

A
  • At a constant temperature the pressure and volume of a gas are inversely proportional
  • pV = constant
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14
Q

What is an ideal gas?

A

A gas which obeys boyle’s law at all temperatures

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15
Q

States Charles’ Law

A
  • At constant pressure, the volume of a gas is directly proportional to its absolute temperature
  • V/T = constant
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16
Q

Describe the graph of volume against temperature for an ideal gas at constant pressure on the degrees Celsius scale

A
  • x axis = absolute zero = -273°C
  • constant gradient
17
Q

Describe the graph of volume against temperature for an ideal gas at a constant pressure on the kelvin scale

A
  • x axis = absolute zero = 0K
  • constant gradient
18
Q

State the pressure law

A
  • At constant volume, the pressure of an ideal gas is directly proportional to its absolute temperature
  • P/T = constant
19
Q

Define the Avogadro constant

A

The number of atoms in exactly 12g of carbon isotope

20
Q

State the equation for the number of molecules

A

N = n(mol) x NA

21
Q

State the equation the combination of the three gas laws give

A

PV/T = constant

22
Q

State the ideal gas equation for n moles

A

pV = nRT

23
Q

State the ideal gas equation for N molecules

A

pV = NkT

24
Q

What is the conversion from litres to volume

A

1000 litres = 1m³

25
Q

State the equation for work done for a gas to expand or contract at a constant temperature

A

Work done = p∆V

26
Q

What does the area under a pressure-volume graph represent

A

The work done

27
Q

What are the assumptions in kinetic theory?

A
  • All molecules of the gas are identical
  • The gas contains a large number of molecules
  • Compared to the container, the molecules’ volume is negligible
  • The molecules continuously move about randomly
  • The motion of molecules follow newton’s laws
  • Collisions between molecules themselves or walls of the container are elastic
  • Between collisions, molecules move in a straight line
  • Forces that act during collisions last for much less time than forces during collisions
28
Q

What are empirical laws, giving an example?

A

Laws which are based of observation and evidence, i.e the gas laws

29
Q

What are theories?

A

Predictions based on assumptions and derivations from knowledge and already developed theories, i.e Kinetic theory

30
Q

Define Brownian motion

A

The motion of a visible particle suspended in a fluid being randomly affected by particles invisible to the human eye

31
Q

What are the units for specific heat capacity?

A

J/KgK

32
Q

When water turns to steam, what happens to its volume?

A

Volume increases 1000x as it expands

33
Q

What is the specific heat capacity of water?

A

4200 J/KgK

34
Q

State 6 assumptions of Brownian motion

A
  • Collision between molecules themselves or between the molecules and walls of the container are perfectly elastic
  • The time during a collision is negligible compared to the time between collisions
  • The molecules continually move about randomly
  • The molecules move in a straight line between collisions
  • The molecules have a negligible volume compared to the volume of the container
  • All molecules of the gas are identical
35
Q

Define thermal equilibrium

A

No net transfer of thermal energy between objects

36
Q

What is the potential energies of each state of matter?

A
  • Solid = Low
  • Liquid = Max
  • Gas = 0, no bonds
37
Q

What are the equations for number of moles?

A
  • n = mass(g)/atomic mass
  • n = mass(g)/molar mass
38
Q

What is the equation for mass(kg) of atoms in a container involving molar mass(kg/mol)?

A

Mass(kg) = molar mass/NA where NA is Avogadro’s constant

AQA A Level Physics(Option A: Astrophysics) (15 decks)

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