3.1 - SPECIMEN SET P1 Q6
6.1)Describe the direction of motion of the particles in a gas [1 mark]
6.2) Explain why heating a gas increases the average speed of the gas particles. [3 marks]
6.3) Water can exist as either a liquid or a gas at 100 °C.
Explain why a mass of gaseous water at 100 °C contains more energy than an equal mass of liquid water at 100 °C. [2 marks]
Water vapour is a gas. Gases change state when they cool.
Figure 8 shows condensation on a cold bathroom mirror.
Density of water = 1000 kg/m3
Specific latent heat of vaporisation of water = 2.26 x 106 J/kg.
Calculate the energy released when the condensation forms. [5 marks]
Energy released = _____________ J
6.5) Central heating boilers burn gas and use the energy released to heat water.
Modern condensing central heating boilers take advantage of the energy that is released when water condenses.
Waste water vapour produced when the water is heated in the boiler is used to preheat the cold water entering the boiler.
Give some of the arguments in favour of condensing boilers compared to older non-condensing boilers. [4 marks]
(Total for Question 6 = 15 marks)