During a laboratory distillation process, a flask is filled with 1.2 kg1.2\text{ kg}1.2 kg of liquid ethanol at an initial temperature of 18∘C18^\circ\text{C}18∘C. An electric immersion heater rated at 1.8 kW1.8\text{ kW}1.8 kW is used to heat the ethanol. The heater is switched on for a duration of 6.5 minutes6.5\text{ minutes}6.5 minutes.
Calculate the total thermal energy supplied by the immersion heater during the 6.5 minutes6.5\text{ minutes}6.5 minutes.
The specific heat capacity of liquid ethanol is 2400 J kg−1 K−12400\text{ J kg}^{-1}\text{ K}^{-1}2400 J kg−1 K−1, and its specific latent heat of vaporisation is 8.5×105 J kg−18.5 \times 10^5\text{ J kg}^{-1}8.5×105 J kg−1. The boiling point of ethanol is 78∘C78^\circ\text{C}78∘C.
Calculate the mass of liquid ethanol remaining in the flask after 6.5 minutes6.5\text{ minutes}6.5 minutes of heating. Assume that all thermal energy from the heater is transferred directly to the ethanol and that no energy is lost to the surroundings or the flask.
56 exam-style questions on OCR A A Level Physics Thermal physics, covering Temperature, Solid, liquid and gas, Thermal properties of materials, and Ideal gases. Each one has a worked solution and a mark scheme showing where the marks go.