Thermochemistry?

May 26, 2017

Heat to evaporate 10 grams HOH = 5400 calories = 22,600 joules

Explanation:

The phase change energy of water can be calculated using
$Q = m \Delta {H}_{t r a n s i t i o n}$ where $m$ is mass and $\Delta {H}_{t r a n s i t i o n}$ is the transition constant per unit mass of water. For evaporation or condensation the constant is Heat of Vaporization $\Delta {H}_{v} = 540 \frac{\text{calories}}{g r a m}$ and for freezing or melting the constant is Heat of Fusion $\Delta {H}_{f} = 80 \text{calories"/"gram} .$ To convert to Joules, use the relationship 4.184 joules = 1 calorie.