A student carries out an experiment to determine the specific latent heat of vaporisation of a liquid. Some liquid in a beaker is heated electrically as shown in the figure below.
Energy is supplied at a constant rate to the heater. When the liquid is boiling at a constant rate, the mass of liquid evaporated in 5.0 minutes is measured. The power of the heater is then changed and the procedure is repeated. Data for the two power ratings are given in the figure below.
Suggest why the rate of evaporation is determined for two different power ratings.
Calculate the specific latent heat of vaporisation of the liquid.
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