Why does ice have a different density than liquid water?

1 Answer
Dr. K.
Jul 31, 2018

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.

http://www.bitlanders.com/blogs/struc-of-liquid-water-and-ice/196084

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.

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