Final answer:
The heat required to vaporize water is calculated with the formula Q = m⋅Lv, where Q is the heat, m is the mass of water, and Lv is the latent heat of vaporization (2256 kJ/kg for water). For instance, to vaporize 685 g (0.685 kg) of water at 100°C, the heat needed is 1546.36 kJ.
Step-by-step explanation:
The formula for calculating the heat required to vaporize (or condense) water is Q = m⋅Lv, where Q is the heat required, m is the mass of the water in kilograms, and Lv is the latent heat of vaporization. The latent heat of vaporization for water is 2256 kJ/kg, meaning that for every kilogram of water you want to vaporize, you would need approximately 2256 kilojoules of energy.
For example, if we want to calculate the amount of heat necessary to vaporize 685 grams (0.685 kg) of water at 100°C, we can use the formula: Q = m⋅Lv = 0.685 kg ⋅ 2256 kJ/kg. To get the heat in kilojoules, we simply multiply the mass by the latent heat of vaporization, resulting in Q = 0.685 kg ⋅ 2256 kJ/kg = 1546.36 kJ.
This calculation can also be used in reverse to find the heat released when water vapor condenses back into liquid water.