Does the amount of heat absorbed as 1 kg of saturated liquid water boils at 100°C have to be equal to the amount of heat released as 1 kg of saturated water vapor condenses at 100°C?

Question

Chemistry

Charlie Hampton

28 September, 16:22

Does the amount of heat absorbed as 1 kg of saturated liquid water boils at 100°C have to be equal to the amount of heat released as 1 kg of saturated water vapor condenses at 100°C?

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Answers (1)

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Tobias Herman · Answer 1

Yes, it does.

Explanation:

When a pure substance changes its phase, the process occurs at a constant temperature. So, for pure water, at 1 atm, both boiling and condensation happen at 100°C. In the first process, the water needs to gain heat, which is called the heat of vaporization, which depends on the mass or number of the moles of the substance.

In the other process, the water must lose heat, which has the same value of the heat of the vaporization, but in a different direction (different signals). That happens because in one process the molecules will be agitated and will separate, in the other, the molecules must be joined together, and be less agitated, so, the process is exactly the opposite of each other, and the energy involved in the same (with opposite directions).