**A Level Specific Heat Capacity Questions**

**Q1. **A domestic room heater which uses natural gas as the fuel, produces an output power of 4.5 kW.

The energy obtained from a cubic metre of this fuel is 39 MJ. The density of the gas is 0.72 kg m^{–3} at atmospheric pressure.

**(a)** Show that the volume of gas which must be burnt to produce a steady output is 6.9 x 10^{–3}
m^{3}
each minute.

**(2 marks)**

**(b)** Calculate

**(i)** the mass of gas which is burnt each minute,

**(ii)** the number of molecules of natural gas which pass through the burner each minute if the molar mass of the gas is 1.6 x 10^{–2} kg mo1^{–1}.

**(4 marks) **

**(c) **When the heater is first turned on, the temperature of the air entering it is 14°C and the temperature of the air leaving it is 36°C. If the specific heat capacity of air is 990 J kg^{–1} K^{–1,} calculate the mass of air passing through the heater in one minute.

**(3 marks) **

**(d) **The room could have been heated using a 4.5 kW electric heater. Explain with a suitable calculation why such a heater could not be operated from a 13 A, 230 V socket.

**(2 marks) **

**(Total 11 marks)**