An electric heater is used to heat an office.
The dimensions of the office are 4.0 m×5.0 m×2.5 m4.0\text{ m} \times 5.0\text{ m} \times 2.5\text{ m}4.0 m×5.0 m×2.5 m. The density of air is 1.2 kg/m31.2\text{ kg/m}^31.2 kg/m3.
Show that the mass of air in the office is 60 kg60\text{ kg}60 kg.
The power of the heater is 1500 W1500\text{ W}1500 W. The specific heat capacity of air is 1000 J/(kg∘C)1000\text{ J/(kg}^\circ\text{C)}1000 J/(kg∘C).
Calculate the time taken to increase the temperature of the air in the office from 15.0∘C15.0^\circ\text{C}15.0∘C to 21.0∘C21.0^\circ\text{C}21.0∘C.
Suggest one reason why the actual time taken to heat the office is longer than the time calculated in (a)(ii).
The office has a double-glazed window consisting of two panes of glass separated by a narrow gap filled with still air. State the main methods of thermal energy transfer from the office to the outside that are reduced by this air gap.
119 exam-style questions on CIE IGCSE Physics 2.2.2a Internal energy and temperature. Each one has a worked solution and a mark scheme showing where the marks go.