amount of energy it takes to boil water
Once the water is at 100 Â°C, still more energy must be added. This is given by the heat of vaporization, which for water is 2261 kJoules per kilogram. So, in the example, once the 1 kg of water. is at 100 Â°C, this amount of energy must be added to boil it: 1 kg * 2261 KJoules/kilogram = 2261 kJoules.