When you freeze things they get smaller but water expands.?

Question

Why is this?

Get real people. these first answers are crap.

If you cool something the molecuses slow down and the item contracts!!!!!!!!

Heating something excites the molecules and it expands.

BUT NOT WATER!!!!!!

Answer 1

Absolutely true, when it freezes to form ice.
Up until that point, water follows the usual rule, and gets smaller, and thus denser. that is why a layer of cool water can lie under a layer of warmer water.
When water changes to ice, however, it forms a crystalline structure, and in this structure the atoms are held further apart than the atoms of water are, even when it is quite cool. This means ice is less dense, floats, and cracks the plumbing.

Answer 2

It is true that most things contract or get smaller when you freeze them. But with water the opposite is the case.

This is because a water molecule(H2O) is what chemists call a 'bent' shape. Imagine a boomerang shape, this is similar to a water molecule. The two ends of the boomerang would represent where the hydrogen atoms are, and the bend in the middle where the oxygen atom is.

The bonds between the hydrogen and oxygen atoms in H2O are made of pairs of electrons. Electrons have a negative charge. The oxygen atom in the middle of the water molecule is what we call 'electronegative', that is it pulls the electrons in the bond towards itself better than the two hydrogen atoms. Because the oxygen atom is 'greedy' for the electrons it becomes slightly negatively charged, which leads to the hydrogen atoms becoming slightly postively charged.

Positive and negative charges attract one another. So the slightly negative oxygen atoms in the water molecule attract the slightly positive hydrogen atoms in neighbouring water molecules. When the water is cooled the water molecules move closer together and more attractions between oxygen atoms and hydrogen atoms form. We call these 'hydrogen bonds'.

Now, remember the water molecule is boomerang shaped. Imagine lots of these held together in a big crystal, this link shows a nice diagram.
http://www.elmhurst.edu/~chm/vchembook/161Ahydrogenbond.html
Because there is a large amount of empty space in the crystal structure of ice it takes up more space than water does.

Answer 3

Water is made up of H2O molecules, which bond to each other through "hydrogen bonds", because the molecules are polar so the hydrogen of one molecule is attracted to the oxygen of another.

In fluid these bonds are bent and transient, but in ice they are fully formed and force the molecules into an open tetrahedral structure, with each molecule being surrounded by four others. This structure takes up more space than the always-shifting structure in liquid water. Hence why water expands on freezing.

It is not the only substance to do so. Silica does for similar reasons. And carbon and I forget which others...

Answer 4

Water is the bomb! Water molecules are the smallest most polar molecules you can get, i.e. the ends (2 Hydrogens) are charged so the molecules all repel each other. When the temperature is lowered the molecules become less excited (imagine getting colder - you reserve energy) so they traditionally become closer. But the Oxygen charge repels other Oxygens, and a magic crystalline structure develops with lots of spaces - therefore increasing the volume of the ice. Or something like that!

Answer 5

Freezing or even just cooling things down from a gas to a liquid to a solid always tend to give lower volumes as they contract. This is mainly to do with the kinetic energy in the molecules, atoms or other type of particles in the substance.

In fact, water also contract on the overall temperature range from steam to liquid water .... BUT there is a special range of temperatures close to it's freezing point where it actually "expands" due to the molecular arrangement.

Answer 6

As water begins to freeze the water molecules align into chains that use up space less efficiently than free water molecules and thus becomes less dense. Icebergs float with about 105% of their weight above the water level due to the greater buoyancy. After water is frozen solid, any further reduction in temperature causes ice to contract just like steel, etc.

Answer 7

Basically, it's because liquid water molecules tend to sort of clump together into groups, but when you freeze water these groups break up, the average distance between water molecules therefore increases slightly, and so ice occupies a larger volume than the same weight of water.

Answer 8

the expansion/ contraction bit is actually because water is unusual in having two stages where it expands, normal stuff like nitrogen, starts off as a gas, cool it and it shrinks, heat it and it expands. Water is pretty much aerated, so you get bubbles in it. But it does have what is known as 'The peculiar property' of having two points on its temperature range where it expands whereas most elements have just one. If you take it as O2 and H2 it doesnt do this

Answer 9

James is right... Freezing causes it to expand.
The reason?
Well qwater is made up of molecules of hydrogen and oxygen. When you heat water....they move very quickly and are close together bouncing all around and then escape as steam.

Cold has the oppostie effect. The molecules slow down and move slowly, spreading apart....hence expanding.
Notice in the winter time in cold climates, that whole concrete slabs will raise up if ice gets underneath it. This is from the water expanding and pushing the slab.
Your avatar is crap.

Answer 10

so far i havent seen a single right answer for this. the shape of the water molecule causes it to begin to form a crystal lattice. this lattice takes up more space than the water normally would simply floating around. think of it like a bunch of legos. if you make a lot of big pieces, they won't fit as easily into the same space as if all the pieces were seperate and small.