# Why does ice have a different density than liquid water?

Jul 31, 2018

It has to do with how the ${H}_{2} O$ molecules are hydrogen bonded to one another in the solid and liquid form.

#### Explanation:

$\mathrm{de} n s i t {y}_{\text{ice}} = 0.934 \frac{g}{c {m}^{3}}$

$\mathrm{de} n s i t {y}_{\text{water}} = 0.997 \frac{g}{c {m}^{3}}$

The difference between the densities has to do with how ${H}_{2} O$ 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 $1 c {m}^{3}$, there will be more water molecules present as compared to ice molecules. That means, $m a s {s}_{\text{water"> mass_"ice}}$

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

$\text{density} = \frac{m a s s}{v o l u m e}$

Since we are looking at same volume, $1 c {m}^{3}$, that means, the density is directly proportional to mass. Therefore, $\mathrm{de} n s i t {y}_{\text{water" > density_"ice}}$

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