AQA PHYSICS A LEVEL 7408 PAPER 2 JUNE 2022

Figure 1 shows an electric steam iron. Figure 1 Water from a reservoir drips onto an electrically-heated metal plate. The water boils and steam escapes through holes in the metal plate. The electrical power of the heater inside the iron is 2.1 kW. Assume that all the energy from the heater is transferred to the metal plate. . The metal plate has a mass of 1.2 kg and is initially at a temperature of 20 °C. The heater is switched on. After a time t the metal plate reaches its working temperature of 125 °C. Calculate t. specific heat capacity of the metal = 450 J kg−1 K−1 [2 marks] t = s . The metal plate is maintained at its working temperature. Water at 20 °C drips continuously onto the metal plate. Steam at 100 °C emerges continuously from the iron. The maker claims that the iron can generate steam at a rate of 60 g min−1. Determine whether this claim is true. specific latent heat of vaporisation of water = 2.3  106 J kg−1 specific heat capacity of water = 4200 J kg−1 K−1 [3 marks] Do not write outside the box Turn over ► . In the kinetic theory model, it is assumed that there are many identical particles moving at random. State two other assumptions made in deriving the equation pV = 1 Nm (crms)2. 3 Do not write outside the box [2 marks] 1 2 . Explain why molecules of a gas exert a force on the walls of a container. Refer to Newton’s laws of motion in your answer. [3 marks] . A sealed flask of volume 0.35 m3 contains an ideal gas at a pressure of 220 kPa. The mean kinetic energy of the gas molecules is 6.7  10−21 J. Do not write outside the box Calculate the amount of gas in the container. [3 marks]