Physics 9702 · AS & A Level · The first law of thermodynamics

The first law of thermodynamics — practice question

(a)[2]

Define specific heat capacity in precise terms.

(b)

A beaker containing a fixed mass of water is at atmospheric pressure.

(b(i))[2]

The water starts at $0^\circ\text{C}$. Thermal energy $E$ is transferred to it, raising its temperature to $8^\circ\text{C}$. There is no net change in the water's volume. Apply the first law of thermodynamics to complete Table 2.1 for this change.

(b(ii))[2]

The water is then heated again, so its temperature rises by another $8^\circ\text{C}$ to a final temperature of $16^\circ\text{C}$. In this process the water's volume increases, so work $W$ is done. Assume that the change in internal energy is the same as in (b)(i). Use the first law of thermodynamics to complete Table 2.2 for this change.

(c)[1]

Using the information in (b), suggest, with a reason, how the average specific heat capacity of water between $8^\circ\text{C}$ and $16^\circ\text{C}$ compares with the average value between $0^\circ\text{C}$ and $8^\circ\text{C}$.

Worked solution & mark scheme

This 7-mark question has a full step-by-step worked solution and mark scheme. One marking point: (thermal) energy required per unit mass (for temperature change)

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