IV.Water+expands+as+it+freezes.+Why+does+water+float?

Jamie Li

Water is connected by hydrogen bonds. When water is hot, the heat easily breaks these bonds and prevents them from "solidifying." As water cools, less heat keeps breaking the bonds, and water molecules are more and more structured by the bonds.

Liquid water

Solid water

The hydrogen bonds want some space between them, so as the bonds strengthen, more empty space appears between them, which is why a given amount of H2O molecules takes up a bigger area as solid water than liquid water.

Since a given amount of H20 molecules takes up more space as a solid, its density (m/v) is less, and thus tends to go to the top, causing it to float.