Why is water the only substance that expands when it freezes?

Question

Why is water the only substance that expands when it freezes?

Answer 1

It is not, liquid ammonia also expands when it freezes.  Ice crystals have a hexagonal structure - as the crystals form, they take up slightly more volume than the liquid.

Answer 2

the molecules are different in water. for example lets take heat for example, the molecules are farther apart, so when water freeze the molecules are close together, which is also call a freezing point.

Answer 3

Water is at its minimum volume at 4 degree celcius. Therefore, it expands when he freezes at 0 degree celcius. However, if the temperature goes down from 10 deg C to 4 deg C the volume condenses.

This is owing to the hydrogen bond inside the water molecule. One hydrogen atom inside the water molecule is attracted to another particular hydrogen atom in another molecule. This is almost like a covalent bond but it isn't one really.

Owing to this bond the molecule changes shape while the temperature drops.

Answer 4

Because the molecules are moving farther away from each other as the water gets colder they are also moving slower too.