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rootofallworlds t1_j71gl75 wrote

Reply to comment by pblack476 in Suppose I have a container of water with a ball floating on top of it. I put it outside overnight and the water freezes. Since the water's volume increases as it freezes, the ball is raised. Where does the increased gravitational potential energy come from? by schematicboy

Ice has less thermal energy than water at the same temperature, which more than offsets the slight increase in gravitational potential energy due to ice Ih (the stable form at STP) being less dense.

On a molecular level, when the water molecules have slowed enough with cooling they can form permanent (ish) hydrogen bonds with each other and the shape of the molecules creates the ice crystal structure, even though this means pushing the molecules apart a bit more.

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