Pressure and Temperature are
directly proportional as long as the
temperature is measured in Kelvins
Pressure Law
Boyle’s Law
Each line represents an experiment done at a different temperature
PistonsWork Done = Force x Change of Distance
Wd = F . Δd
but
Wd = P.A.Δd
Wd = P. ΔV
Wd = P. ΔVAs long as there is an AREA under the line then you can see that work is done (and calculate it)
𝑄=∆𝑈+𝑊First Law of Thermodynamics
It just says that if you add Heat to a gas it must be equal to the Work Done by the gas + any change in Internal Energy
This is mainly difficult because:
1. Heat can be gained or lost2. Internal Energy can rise or fall3. Work can be done ‘on the gas’ or ‘by the gas’
1. Isobaric
1. The gas is expanding – doing Work (Work is +ve)2. The temperature is increasing so ΔU is increasing (ΔU is +ve)3. ΔQ = ΔU + W so Q must be +ve 4. Heat must have been added
ConstantPressure
2. Isovolumetric / Isochoric
1. The gas isn’t expanding or contracting. No Work is done. ΔW=02. Because the Pressure is increasing the temperature must be
rising so ΔU is +ve3. Q = ΔU + W so Q = ΔU so heat is +ve4. Heat must have been added
ConstantVolume
3. Isothermic
1. The gas is expanding – doing Work (Work is +ve)2. The temperature is constant so ΔU is 03. Q = ΔU + W so Q =W4. Heat must have been added to enable the gas to do work
ConstantTemperature
4. Adiabatic
1. No heat is exchanged so Q = 02. Volume is reducing so Work is being done ON THE GAS (W= -ve)3. Q = ΔU + W so 0 = ΔU - W 4. ΔU = W so work done on the gas increases the Internal energy of
the gas
No Heat is being exchanged –
perfectly insulated.
Adiabatic lines are always steeper than Isotherms
A Heat CycleA-BIsochoric / Isovolumetric Temperature rise
B-CIsobaric Expansion
C-DIsochoric / IsovolumetricTemperature drop
D-AIsobaric Contraction
The Carnot Cycle
Forward Carnot Cycle
D
Reverse Carnot Cycle