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A-level Physics Year 2 > Thermal Physics > Flashcards

Thermal Physics Flashcards

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1
Q

What is Internal energy of gas ?

A

The sum of the randomly distributed kinetic and potential energies of its particles

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2
Q

Absolute temperature scale

A

K = C + 273
- 0k is lowest possible temperature that any object can theoretically have
(K - Kelvins + C - Celsius)

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3
Q

What happens to the internal energy of a system when energy is transferred to it ?

A

Increases ( Visa Versa)

- average speed of particles increase

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4
Q

How can (heat) energy be transferred between substances ?

A

by the collision of particles

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5
Q

What is Specific heat capacity (C) ?

A

The amount of heat energy required to change 1kg of material by 1 Kelvin

  • Measured in JKg-1K-1
  • heating will result in a change of temperature
  • kinetic energy
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6
Q

Specific heat capacity formula

A

Q = mcΔt

heat energy = mass x SHC x change in temperature

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7
Q

What is a Continuous Flow (Calorimeter) ?

A

A fluid flow continuously over a heating element. As its flows, energy is transferred to the fluid.

  • Help measure the SHC (change the p.d)
  • Q = mcΔt + H ( H is the heat lost to the surroundings)
  • random error is fluctuations in temperature of the water flowing in and systematic error is thermometers may not be exactly calibrated
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8
Q

What is Specific latent heat (L) ?

A

The amount of heat energy required to change the state of 1kg of material

  • Measured in JKg-1
  • heating will result in change of state
  • potential energy
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9
Q

Specific latent heat formula

A

Q =ml

heat energy = mass x SLH

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10
Q

What are the types of SLH ?

A

SLH of fusion - solid/liquid transitions
- solid -> liquid = melting
- liquid -> solid = solidifying
SLH of vaporisation - liquid/gas transitions
- liquid -> gas = vaporising
- gas -> liquid = condensing

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11
Q

What is change of state ?

A

when a substances changes between a solid, liquid and gas. (potential energy of particles changes)

  • when the substances changes state, the temperature remains the same as kinetic energy of particles remain the same
  • graph (temperature/internal energy)
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12
Q

What is Boyle’s Law ?

A

ideal gas at a constant TEMPERATURE (K) the pressure and volume are inversely proportional

  • p ∝ 1/V (pV = constant)
  • graph (pressure/volume) - curve (don’t touch axis’s)
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13
Q

What is Charles’s Law ?

A

ideal gas at a constant PRESSURE (Pa) the volume is directly proportional to its absolute temperature

  • V ∝ T (V/T = constant)
  • graph (volume/temperature) - straight line
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14
Q

What is Pressure Law ?

A

ideal gas at a constant VOLUME (m^3)the pressure is directly proportional to its absolute temperature

  • p ∝ T (p/T = constant)
  • graph (pressure/temperature) - straight line
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15
Q

Explain Boyle’s Law

A
  • constant temperature = particles speed remain the same
  • volume decreased = more collisions per second
  • rate of change of momentum increases
  • force increases = pressure increases
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16
Q

Explain Charle’s Law

A
  • temperature increases = particles move at a greater speed (more KE)
  • to maintain constant pressure = volume must increase
  • so longer journey between collisions between particles
  • constant rate of change of momentum = constant force = constant pressure
17
Q

Explain Pressure Law

A
  • temperature increases = particles move at a grater speed (more KE)
  • to maintain constant volume = pressure must increase
  • particles rate of change of momentum increases
  • increases force (on walls) = increased pressure
18
Q

What is Molecular mass ?

A

the sum of the masses of all the atoms that make up a single molecule (relative atomic mass)
- e.g. C02 is 12+16+16 = 44

19
Q

What is the Avogadro constant (NA) ?

A

is the number pf atoms in exactly 12g of the carbon isotope 12/6 C

  • 6.02 x 10^-23 mol-1
  • at fixed volume of gas at a fixed temperature and pressure
20
Q

what is Molar mass of a substance ?

A

is the mass that 1 mole of that substance would have (equal to its relative molecular mss)
- e.g. helium is 4g because RAM = 4.0

21
Q

Calculate the number of molecules (N) in a substance ?

A

N = nNa

  • number of molecules = number of moles x Avogadro constant
  • number of moles measured in ‘mol’
22
Q

What is the ideal gas equation ?

A

PV = nRT
- combine the three laws -> PV/T = constant -> pV/T = nR
(pressure x volume = number of moles of gas x MOLAR GAS CONSTANT x Temperature)

23
Q

What is the Boltzmann Constant (k) ?

A 
k = R/Na
(Boltzmann = Molar gas constant/Avogadro constant)
(Na = N/n) -> (Nk = nR) -> pV = NkT
24
Q

How to calculate WORK DONE on a gas ?

A

Work done = pΔV

  • work done = energy transferred
  • constant pressure - Charle’s law
  • area under the graph =energy transferred to change volume of gas
25
Q

Derive the equation for the pressure exerted by an ideal gas ?

A

1) change in momentum -> mu - (-mu) = 2mu
2) time between collisions -> 2l/u (distance/velocity)
3) force -> mΔt/t -> 2mu/(2l/u) -> mu^2/l
4) pressure = F/A -> mu^2/l^3 -> mu^2/V
(only for one particle)
5) N_u^2 = average
6) total pressure = mu^2/v = Nm_u^2/V
_u^2 =1/3_c^2
EQUATION -> pV = 1/3 Nm_c^2 -> pV = 1/3 Nm (Crsm)^2
_c^2 = Crsm^2 = root mean square speed (typical speed)

26
Q

Assumptions made in ‘kinetic theory’ ?

A
  • molecules act as point masses ( no volume)
  • all molecules of gas are identical
  • molecules continually move about randomly
  • molecules move in a straight line between collisions
  • time of collisions are negotiable (small) compared to time between collisions
  • collisions are perfectly elastic (between wall and particle)
27
Q

How to calculate the kinetic energy of gas molecules ?

A

1/2m(Crsm)^2 = 3/2kT = 3RT/2Na

  • equation made from ideal gas equation and kinetic theory equation
  • total kinetic energy - need to know number of molecules e.g. (1/2m(Crsm)^2) x n x Na
28
Q

What are Empirical Laws ?

A

are laws based on observations and evidence e.g. the gas laws including the ideal gas law.
- the opposite it theoretical laws - based on theory (predicted and explained) e.g. kinetic theory

29
Q

How have the behaviour of gases have changed over time ?

A

at first the three gas laws were developed by a-lot of scientists
- daniel BERNOULLI - explained Boyle’s law

30
Q

What is the Brownian Motion ?

A

is the type of movement of any particles suspended in a fluid

  • provided evidence for the existence of atoms by noticing pollen grains in water moved with a zig-zag, random motion
  • helps the idea that everything is made from atoms

A-level Physics Year 2 (7 decks)

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