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.
528 exam-style questions on CIE IGCSE Physics 2.2 Thermal properties and temperature, covering 2.2.1 Thermal expansion of solids, liquids and gases, 2.2.2a Internal energy and temperature, 2.2.2b Specific heat capacity, 2.2.3a Melting, boiling, condensation and solidification, 2.2.3b Evaporation, and 2.2.3c Cooling by evaporation. Each one has a worked solution and a mark scheme showing where the marks go.