Physics 9702 · AS & A Level · The first law of thermodynamics
The first law of thermodynamics — practice question
An ideal gas begins with pressure $1.0 \times 10^5\,\text{Pa}$, volume $4.0 \times 10^{-4}\,\text{m}^3$ and temperature $300\,\text{K}$, as shown in Fig. 2.1. A change in the gas’s energy of $240\,\text{J}$ raises the pressure to a final value of $5.0 \times 10^5\,\text{Pa}$ while the volume stays constant. The thermodynamic temperature is $T$.
(a(i))[2]
Calculate the final temperature $T$.
(a(ii))[2]
Calculate the amount of gas present.
(b(i))[2]
A system’s increase in internal energy may be written as $\Delta U = q + w$. State what is meant by 1. $+q$, 2. $+w$.
(b(ii))[3]
State, for the gas in (a), the values of 1. $\Delta U$, 2. $+q$, 3. $+w$.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Either $p\propto T$ or $\frac{pV}{T}=\text{constant}$ or $pV=nRT$” …