Why does water get bigger when frozen?

Question

Most things get denser (smaller) when cooled. Why not H2O?

Answer 1

because the molecules spread apart when in a solid (solid molecules are farther apart then liquid molecules)

Answer 2

Water in it's liquid form is remarkably "dense and compact" - in other words the water molecules fit quite closely together. This is because each water molecule acts like a tiny magnet and they all line up and fit snugly one against the next.

To explain: water (H2O) consists of one Oxygen atom bonded to two Hydrogen atoms. The molecule takes the form of a "V" shape with the Oxygen at the base of the "V" and the Hydrogens at each top end. The Oxygen forms the "negative" end of the magnet and the Hydrogens make the "positive" end.

When water is crytalised (ie frozen) it forms a hexagonal crystal structure as bonds called Hydrogen Bonds are formed which hold the water molecules further apart so that ice is about 8% less dense than water (this is why ice floats on water) and this also explains why water expands when it freezes - the Hydrogen Bonds force the water molecules further apart making the volume larger.

Check out the wikipedia link for a whole lot more on ice - like did you know there are 14 different forms of ice? (and I bet none of them are flavoured and come on a stick!)

Answer 3

Water does not get bigger when it is frozen. Actually, it is warm water that expands. It may look bigger because of the shape of the container. Try this: Fill an ice cube tray half way. Wait a couple of hours. When it is frozen, you will notice that the ice did not overflow.

Answer 4

Liquid water molecules are composed of two hydrogens each attached to an oxygen. These molecules are polar- the oxygen has a negative dipole and the hydrogens have positive dipoles. These dipoles allow INTERMOLECULAR hydrogen bonding, which increases the density of water as a liquid. When you freeze water, these hydrogen bonds between water molecules are interruped by the water becoming crystalized. The density of water when it is frozen (ice) is LESS than liquid water, yet the ice crystals are arranged in their solid form in a way that makes the entire substance expand.

Answer 5

usually on freezing stuff becomes smaller and on heating they expand...for example metal, when heated expands and when cooled it shrinks
however the case of water is different.. up to a certain level it shrinks and then when it reaches the maximum density it expands...this is because water crystallizes into an open hexagonal form. to every oxygen atomthere are two hydrogen atoms attached to form a water molecule...when water is frozen the distace between the bond that hold oxygen and hydrogen together increases and hence water expends when frozen

Answer 6

I take it because it crystalizes, but that's funny since usually molecules constrict and become more dense and non-free flowing in reaction to the cold, but speed up and expand in reaction to heat. On the other hand, a snow flake can easily be bigger than a rain drop, given the properties of water's reaction to temperature. It turns to vapor if hot enough.

Answer 7

Because water molecules are packed tightly and ice molecules are packed less tightly, 4 molecules pack together to form a crystal-looking thing. So there is more extra space between the molecules. Hope that's a little bit easy to understand.

Answer 8

Because when it frozen it's not water anymore it's ice! It's a solid! In order for the water to become ice it must take on a different form. It therefore must expand in order to take on it's new form.

Answer 9

Because the molucules in frozen water expand by moving faster.

Answer 10

yes most things do that's what makes water so special. it's less dense in its solid form because of the thermocline. it's a property that is highly sought after but few materials have.