A student heats 0.25 kg0.25\text{ kg}0.25 kg of water in a beaker until it evaporates into steam. The starting temperature of the water is 22∘C22^\circ\text{C}22∘C.
The specific heat capacity of water is 4200 J/kg∘C4200\text{ J/kg}^\circ\text{C}4200 J/kg∘C. Calculate the energy needed to raise the temperature of the water to 100∘C100^\circ\text{C}100∘C.
The specific latent heat of vaporisation of water is 2 260 000 J/kg2\,260\,000\text{ J/kg}2260000 J/kg. Calculate the energy needed to turn all the water at 100∘C100^\circ\text{C}100∘C into steam.
Use your answers from (a)(i) and (a)(ii) to calculate the total energy needed to turn 0.25 kg0.25\text{ kg}0.25 kg of water at 22∘C22^\circ\text{C}22∘C into steam at 100∘C100^\circ\text{C}100∘C. Write your answer in standard form and to 2 significant figures.
Suggest two reasons why the actual electrical energy needed from a heater in a real experiment would be more than the calculated value in (a)(iii).
Suggest one advantage of repeating an experiment three times and calculating a mean.