Does water contract as it freeze?

Answer 1

Water is really strange stuff, because of the very strong hydrogen-oxygen bonds. One odd thing is that water is most dense at 4 deg C -- that's why lakes freeze from the top down; the warmer water sinks.

Every substance expands when you heat it -- because the average space between the atom's nuclei increases when the atoms have more energy (vibrating faster, more heat). So water DOES expand when you heat it, like anything else -- it's only when it freezes and crystallizes that the weirdness (expansion of ice) happens.

The reason water expands when frozen is the crystalline structure that forms, and those strong O-H bonds. The hydrogen atoms have a very strong attraction for the unbonded electrons in the nearby molecules. In an ice crystal, each oxygen atom has it's own 2 electrons, and grabs hold of 2 more electrons from the water molecule next door. And so they crystallize into a big hexagon shape, which takes up more space than the same molecules do when the water is in liquid form. An ice crystal's form is called a 'network structure.' Same molecules, but takes up more space.

Answer 2

Yes, water contracts as it freezes. This is because the molecules in water form a crystalline structure when freezing, causing them to arrange in a more ordered and spaced-out manner, leading to a decrease in volume.