Beginner Topic 414 of 1102 Thermodynamics & Energetics
Heat of Vaporization of Water
About 2260 joules per gram are required to vaporize water at 100 degrees Celsius.
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In-depth explanation of Heat of Vaporization of Water
The heat of vaporization of water is about 2260 joules per gram at its boiling point of 100 degrees Celsius under atmospheric pressure. This large value results from the hydrogen bonds that must be broken as molecules escape from the liquid into the gas phase. The high energy requirement explains why sweating cools the body so effectively, since evaporation draws heat from the skin. Steam at 100 degrees Celsius contains much more energy than liquid water at the same temperature because of this latent heat. Industrial steam heating and power generation depend on exploiting this energy.
Going deeper: Heat of Vaporization of Water
Key ideas: Use q equals m times 2260 J per gram at 100 degrees Celsius, or 40.7 kJ per mole. The value decreases at higher temperatures, and it is larger than the heat needed to warm the water from 0 to 100 degrees, which is only 418 J per gram.
Common mistakes and connections: Mistakes are forgetting to convert between grams and moles and mixing up fusion with vaporization values. High heat of vaporization makes water an ideal coolant and moderates climate. It connects with hydrogen bonding and with sweating as a cooling mechanism.
Visualization of Heat of Vaporization of Water
Water's high heat of vaporization (40.7 kJ/mol, 2260 J/g) means vapour pressure rises steeply with temperature, reaching 1 atm at 373 K. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Boiling away 1 kg of water at 100 degrees Celsius requires about 2.26 megajoules of heat, far more than warming the same water by a few tens of degrees.
Frequently asked questions about Heat of Vaporization of Water
What is Heat of Vaporization of Water?
About 2260 joules per gram are required to vaporize water at 100 degrees Celsius.
Is Heat of Vaporization of Water a beginner, intermediate or advanced topic?
Heat of Vaporization of Water is a beginner topic in Thermodynamics & Energetics. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Heat of Vaporization of Water?
Study these earlier topics in Thermodynamics & Energetics first: Standard Conditions, Calorie vs Joule, Heat of Fusion of Ice.
What comes after Heat of Vaporization of Water?
The next topics in Thermodynamics & Energetics are Thermodynamics of Dissolution and Gibbs-Helmholtz Equation.
Can I practise Heat of Vaporization of Water with quizzes?
Yes. The interactive lesson includes a self-check question on Heat of Vaporization of Water, and the Thermodynamics & Energetics quiz draws on every topic in this area.
Where Heat of Vaporization of Water fits in Thermodynamics & Energetics
Heat of Vaporization of Water is topic 86 of 91 in Thermodynamics & Energetics.