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1.5 g of water at 100 °C boils at 1.013 × 10⁵ Pa…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
of water at boils at . The of water becomes of steam. The latent heat of vaporisation is . Find the work done by the water as it expands and the change in its internal energy.
Need a reminder? The key ideaShow
The first law: . is positive when heat goes into the gas; is positive when the gas does work on its surroundings, so work done on the gas is negative. For an ideal gas, means it gets warmer.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Work. .
Step 2. Heat. .
Step 3. First law. .
Answer: of work; the internal energy rises by .
Check. Most of the heat, about , pulls the molecules apart; only a little pushes back the air.
Watch out. .
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