Thermodynamics
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- Created by: chalky-nerd
- Created on: 14-03-21 18:11
How do you find the amount of energy required to change the temperature of a substance?
ΔE = mcΔθ
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What is specific heat capacity?
c, Energy per unit mass per degree change in temperature, without a change in state
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How do you find the amount of energy needed to change state?
ΔE = LΔm
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What is specific latent heat?
L, Energy per unit mass to change state, without changing temperature
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What is internal energy?
Sum of all the kinetic energies and potential energies of all particles
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How does the state of the substance affect its internal energy?
When a substance changes state, its internal energy changes
Potential energies change
Kinetic energies constant
Potential energies change
Kinetic energies constant
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What is absolute zero?
0 Kelvin, -273.15°C
Where particles have no kinetic energy and volume and pressure of a gas are both 0
Where particles have no kinetic energy and volume and pressure of a gas are both 0
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What are the assumptions in the kinetic theory model?
No intermolecular forces act on the molecules
Duration of collisions is negligible
Motion of molecules is random
Collisions are perfectly elastic
Motion of molecules follow Newton's Laws
Molecules move in straight lines between collisions
Duration of collisions is negligible
Motion of molecules is random
Collisions are perfectly elastic
Motion of molecules follow Newton's Laws
Molecules move in straight lines between collisions
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What is an ideal gas?
An ideal gas follows pV = NkT for all T and p.
No other interaction than perfectly elastic collisions between particles.
Therefore no intermolecular forces.
No potential energy.
Internal energy = Kinetic energies.
No other interaction than perfectly elastic collisions between particles.
Therefore no intermolecular forces.
No potential energy.
Internal energy = Kinetic energies.
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pV = NkT
(pressure)(volume) = (number of molecules)(boltzmann constant)(temperature)
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pV = nRT
(pressure)(volume) = (number of moles)(universal molar gas constant)(temperature)
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Average KE of molecules
1/2m <c^2> = 3/2kT
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How to derive 1/2m<c^2> = 3/2 kT
1/3 Nm<c^2> = NkT
Rearrange
Rearrange
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What is a black body radiator?
A perfect emitter and absorber of all possible wavelengths of radiation
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What are radiation curves?
Intensity against wavelength of radiation emitted
For a BBR curves are bell curves with peak shifted to the left
For a BBR curves are bell curves with peak shifted to the left
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What is the Stefan-Boltzmann Law?
Luminosity of a black body radiator is proportional to surface area and (absolute temperature)^4
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What is the equation or the Stefan-Boltzmann Law?
L = σAT^4
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What is the Stefan-Boltzmann Law used for?
Comparing stars' size, power output, temperature
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What is Wien's Law?
Peak wavelength of emitted radiation is inversely proportional to the absolute temperature
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What is the equation for Wien's Law?
λ(max)T = 2.898 x 10^-3 metres-Kelvin
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How do black body radiators show Wien's Law?
Peak wavelenth of BBR falls when temperature rises - Frequency increases - Energy of wave increases
BBR show Wien's Law on radiation curves
BBR show Wien's Law on radiation curves
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How to derive pV = 1/3 Nm<c^2> (1)
Consider a particle moving horizontally with mass m and velocity u in a cube of side length L
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How to to derive pV = 1/3 Nm<c^2> (2)
Impluse of particle on wall = mu - (-mu) = 2mu
Time between collisions = 2L/u
Time between collisions = 2L/u
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How to to derive pV = 1/3 Nm<c^2> (3)
Force = Δp/t = 2mu/2L/u = mu^2/L
Pressure = F/A = mu^2/L/L^2 = mu^2/L^3 = mu^2/V
Pressure = F/A = mu^2/L/L^2 = mu^2/L^3 = mu^2/V
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How to to derive pV = 1/3 Nm<c^2> (4)
Total pressure = sum of individual pressures
p =m(u1^2 + u2^2 +...+un^2)/V
p =m(u1^2 + u2^2 +...+un^2)/V
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How to to derive pV = 1/3 Nm<c^2> (5)
Instead of considering each speed separately, use mean square speed <u^2>
Then N<u^2> = sum of indiviual speeds
p = Nm<u^2>/V
Then N<u^2> = sum of indiviual speeds
p = Nm<u^2>/V
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How to to derive pV = 1/3 Nm<c^2> (6)
Only considered horizontal motion, but there are 3 dimensions
<c^2> = <u^2> + <v^2> + <w^2>
Motion is completely random so assume that <u^2> = <v^2> = <w^2>
So <c^2> = 3<u^2>
<c^2> = <u^2> + <v^2> + <w^2>
Motion is completely random so assume that <u^2> = <v^2> = <w^2>
So <c^2> = 3<u^2>
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How to to derive pV = 1/3 Nm<c^2> (7)
p = Nm<c^2>/3V
pV = 1/3 Nm<c^2>
pV = 1/3 Nm<c^2>
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What is Boyle's Law?
Pressure of a fixed mass of gas is inversely proportional to its volume
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What is pressure proportional to?
Temperature
P1/T1 = P2/T2
P1/T1 = P2/T2
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What is pressure inversely proportional to?
Volume
P1V1 = P2V2
P1V1 = P2V2
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What is volume proportional to?
Temperature
P1V1/T1=P2V2/T2
P1V1/T1=P2V2/T2
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Other cards in this set
Card 2
Front
What is specific heat capacity?
Back
c, Energy per unit mass per degree change in temperature, without a change in state
Card 3
Front
How do you find the amount of energy needed to change state?
Back
Card 4
Front
What is specific latent heat?
Back
Card 5
Front
What is internal energy?
Back
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