CAIE A-Level Physics 16.2.2 Applying ΔU = q + W
Practise applying the first law delta U = q + W to heating, cooling, compression, expansion and cycles, calculating energy changes and tracking signs.
- Syllabus
- 2028–2030
- Course
- Physics 9702
- Level
- A2
Exam points
- apply the first law ΔU = q + W with the stated convention for heating and work done on the system
- calculate internal-energy change, heat transfer or work from the first-law equation
- construct an energy balance for a thermodynamic process and interpret positive or negative terms
- distinguish work done by the gas from work done on the gas when applying the first law
16.2.2—The first law of thermodynamics ∆U = q + W expressed question 1
[Maximum number: 3]
The gas in (b) is allowed to return to its starting temperature. The piston is now fixed in position.
Thermal energy is supplied to increase the temperature to the same final temperature as in (b).
Use the first law of thermodynamics to suggest and explain how the specific heat capacity of the gas for this situation compares with the value in (b)(iii).
no change in volume so no work is done (by the gas)
B1
(same temperature change so) same change in internal energy
B1
less thermal energy needs to be supplied so c is less
B1
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