Paper 1 Thermal Physics B Answers

Q	Ans	Brief reason
1	A	Ideal gas collisions are elastic.
2	B	Pressure comes from wall momentum changes.
3	B	Mean translational kinetic energy is $3kT/2$.
4	B	Thermodynamic temperature required.
5	B	Molecules $N=n{N}_A$.
6	A	Boyle law.
7	C	For ideal gas, $U$ depends on $T$.
8	A	Work on gas raises internal energy if no heating.
9	C	No volume change means no boundary work.
10	A	Area under p-V curve gives work by gas.
11	A	Ideal gas internal energy depends only on temperature.
12	A	Avogadro constant.
13	A	$c_{rms}\propto \sqrt{T}$.
14	A	Charles law.
15	A	First law is energy conservation.
16	B	Heat is energy transfer, not stored state property.
17	A	Constant-pressure boundary work.
18	A	State returns to initial value.
19	A	Isotropy gives equal components.
20	A	Intermolecular effects are smallest then.