Question

Why does ice have a different density than liquid water?

Answer 1

It has to do with how the `H_2O` molecules are hydrogen bonded to one another in the solid and liquid form.

Explanation:

`density_"ice" = 0.934 g/(cm^3)`

`density_"water" = 0.997 g/(cm^3)`

The difference between the densities has to do with how `H_2O` molecules are hydrogen bonded in solid (ice) versus liquid (water) form.

From the image above, notice how the ice molecules (image on left) are connected in a more rigid manner. The liquid water molecules (image on the right) on the other hand are connected closer to each other.

This means, in a given volume, let's just say `1 cm^3`, there will be more water molecules present as compared to ice molecules. That means, `mass_"water"> mass_"ice"`

So, if we were to look at the formula of density:

`"density" = (mass)/(volume)`

Since we are looking at same volume, `1 cm^3`, that means, the density is directly proportional to mass. Therefore, `density_"water" > density_"ice"`

That's why, density of water is higher than density of ice.