Final answer:
As temperature increases and water turns to gas, all hydrogen bonds in the water are completely broken due to the high kinetic energy of the water molecules. They then escape into the air as water vapor. In contrast, when water freezes, molecules form a crystalline structure through hydrogen bonds, making ice less dense than water.
Step-by-step explanation:
When the temperature increases and liquid water changes to gas, what happens to the hydrogen bonds within the water molecules? As the temperature increases, these hydrogen bonds are not just weakened; they are actually broken completely.
In liquid water, these bonds are constantly being formed and broken as the water molecules move past one another.
However, when the water begins to boil, the increased kinetic energy of the water molecules—due to the high temperature—causes these hydrogen bonds to break completely. This allows the water molecules to escape into the air as water vapor or steam.
Conversely, when water cools and freezes, the molecules slow down and form a crystalline structure held together by hydrogen bonds, leading to ice that is less dense than liquid water.