why does a glass of water expands when put inside the refigerator?

Question

everytime i put water inside the freezer, when it becomes ice, it expands. isn't it when a substance reach a low temperature, the substance contracts?

oh, i remember. when it turns to ice, it has bubble-like something inside.

Answer 1

Everyone (except MrBoby, he's close) seems to have skipped the most important thing, which is WHY the crystal structure of ice is less dense than when it exists as water.

Sure, the answers about 4 degrees centigrade and lower are correct. But you must remember that above 4 degrees centigrade the thermal energy is greater than the binding energy of the hydrogen bond.

'That what?' I hear you ask. The hydrogen bond is due to the shape of the water H2O molecule. As someone else already said, it is like a U shape (more like a V shape really). Let's picture that V shape now in our heads. The top two points are hydrogen, the bottom point is oxygen. Hydrogen only has one proton in the nucleus, and only one electron orbiting it. As H2O bonds covelently, the probability density function of the electron in the hydrogen atoms changes such that the electron is more likely to reside somewhere in between the oxygen and the hydrogen. This means that the positive nucleii of the two hydrogen atoms is not cancelled out by the average position of the orbiting negative charge of the electrons. In otherwords, your V-shaped molecule becomes a dipole, with a positive charge at the top and a negative charge at the bottom.

Now this is the important bit. When the temperature is above 4 degrees centigrade the molecules have so much energy they are randomly aligned and moving about. When you cool it below 4 degrees centigrade, the thermal (and hence, kinetic) energy of the molecules is less than the binding energy of this attractive dipole force. The positive part of one V-shaped molecule is attracted to the negative part of the next V-shaped molecule. Sure, they were always attracted to each other, but now the heat was low enough that they could expresses that attraction (if you see what I mean).

So, the V-shaped molecules all attempt to line up. If water was an X-shaped dipole it wouldn't make as much of a difference, but because the V-shaped molecules can't tessilate perfectly (due to the attractive/repulsive coulomb force produced by the dipoles), the water takes up more room and is less dense. This is called the hydrogen bond. It is similar to the Van der Waals bond.

And THAT is why ice takes up more room than the same mass of water.

Can I have 10 points now please?

Answer 2

What a lot of the other respondants have said is true. However it is the fact that the molecules are free to move around that would normally mean they are free to move apart and make the liquid less dense and take up more space than the solid form. As is the case for most matter.
i.e. in most matter the dense crystal/solid strcture breaks appart. (Think exploding) with more energy into the liquid form.

However in water the polarity of the molecules means that there is a residual weak attractive force between the hydrogen atoms of one molecule and the oxygen atoms of another, thus drawing them together. In effect the open crystal structure of ice collapses into water.

It is certainly a contributing factor that the shape and movement of the individual molecues of water mean that the structure of ice is a relatively open crystal lattice.

Answer 3

Simon_c has a great answer. In liquid water the molecules are arranged randomly and can tumble and slide over one another. As water cools from room temperature it begins to contract as the water molecules slow down to form thier solid lattice structure. At about 4 degrees Celcius the lattice structure is beginning to take shape. As the water freezes, the polar nature of the water molecules actually pushes them away from each other, making ice less dense then water.

This is actually pretty cool if you think about. If this was not the case, life on Earth would not be possible as lakes and rivers would freeze from the bottom up instead of the top down, killing all life within them.

Answer 4

In the liquid state the water molecules are packed more closely together and have no set configuration. At 4degrees celsius water forms a perfect lattice meaning each molecule is now arranged in a specific manner to form a crystal. This arrangement takes up more space than the previously packed molecules and as the water freezes the crystalline structure holds this expanded arrangement although not necessarily in the perfect lattice held at 4 deg C

Answer 5

Its nothing fundamental to do with the bubbles which is the dissolved gas coming out of solution. Most liquids do get denser when they freeze. Fortunately for fishes and frogs in lakes water is one of the odd ones. It starts to expand at +4C on cooling and so ice floats.

Answer 6

When water freezes the molecules align to form a crystalline solid structure (ice) which takes up more space between the molecules than free flowing water does.

The bubble-like thing your thinking of is the space between the ice structure.

Answer 7

Liquid expands when it is cold, thus slightly expanding, or stretching the glass. And yes, a lower temperature will contract the materials. Actually, if a glass of water is left in a freezer, it most likely will shatter, because of expansion. Water is the only compound that will expand.

Answer 8

Maybe the container that you have the water in just contracts more than the water, giving it the appearance of the water /ice growing?

Answer 9

the H2o molecules are sort of U shaped so when they are set into a form then don't really fit together hence the expanded volume

Answer 10

Its because water expands when it freezes. It called the anomalous expansion of water.