Question

Which contains more heat, 1 kg of water at 100° C or 1 kg of steam at 100° C ? Give reason for your answer.

Answer 1

Latent heat of vaporisation of water is 22.5 × 10⁵ J/kg. It means that 22.5 × 10⁵ J of heat is required to change 1 kg of water at 100°C into steam at the same temperature. It means that 1 kg of steam at 100°C has 22.5 × 10⁵ J more energy than 1 kg of water at the same temperature.

In other words, when the temperature of water is raised, it starts getting converted into steam, as soon as the latent heat of vaporization is achieved. Since, water gets converted into steam on gaining heat, steam has more heat than water at the same temperature, in this case, 100°C. Steam gets converted into water on loosing this heat.