Paper 3 Thermal Physics A Answers

Q1 Multi-stage heating

1. Warm ice from $-15^{\circ }\mathrm{C}$ to $0^{\circ }\mathrm{C}$; melt ice at $0^{\circ }\mathrm{C}$; warm water from $0^{\circ }\mathrm{C}$ to $25^{\circ }\mathrm{C}$. [3]
2. $Q_1=0.120(2100)(15.0)=3.78\times 10^3\mathrm{J}$. $Q_2=0.120(3.34\times 10^5)=4.01\times 10^4\mathrm{J}$. $Q_3=0.120(4200)(25.0)=1.26\times 10^4\mathrm{J}$. Total $=5.65\times 10^4\mathrm{J}$. [5]
3. Temperature rises to $0^{\circ }\mathrm{C}$, stays flat during melting, then rises to $25^{\circ }\mathrm{C}$. [2]

Q2 Thermometer calibration

1. Fraction of range $=(15.0-4.0)/(24.0-4.0)=0.550$, so $\theta =55.0^{\circ }\mathrm{C}$. [3]
2. It should expand uniformly/reproducibly, not wet the glass, remain liquid over range, be visible, and have suitable sensitivity. [2]
3. Calibration links the thermometric property to known fixed points so readings can be converted to temperature. [2]