Physics 9702 · AS & A Level · The first law of thermodynamics
The first law of thermodynamics — practice question
An ideal gas starts 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 $240\,\text{J}$ causes the pressure to rise to a final value of $5.0 \times 10^5\,\text{Pa}$ while the volume stays constant. The thermodynamic temperature is now $T$.
(a(i))[2]
Calculate the temperature $T$.
(a(ii))[2]
Calculate the amount of gas.
(b(i))[2]
The increase in internal energy $\Delta U$ of a system may be represented by the expression $\Delta U = q + w$. State what is meant by the symbol (1) $+q$, (2) $+w$.
(b(ii))[3]
State, for the gas in (a), the value 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: “$p\propto T$ or $\dfrac{pV}{T}=\text{constant}$ or $pV=nRT$” …