First-law problems and the second law
Answers are for parents and teachers.
1
A monatomic gas expands isobarically by 0.01 m³ at 200 kPa. Find A, ΔU and Q (J).
A = 2000, ΔU = 3000, Q = 5000
2
A gas receives 700 J of heat and its internal energy rises by 200 J. The work done by the gas?
500
3
In an adiabatic process a gas does 150 J of work. ΔU = ?
–150 J
4
Write three everyday examples each of reversible-like and irreversible processes.
Reversible-like: pendulum, spring, an elastic ball bouncing; irreversible: cooling, mixing, breaking.
5
Can cold tea boil by itself? Explain with the second law.
No: heat does not pass spontaneously from the cooler surroundings into the tea to heat it; external energy is needed.