/sci/ - Science & Math

http://lmgtfy.com/?q=Why+does+water+expand+when+frozen%3F

Ice expands because when it it gets colder, the water molecules move more slowly, and tend to line up into a lattice structure, and they take up more room like than than they so when they're bouncing around. Ice floats because it expanded, but it's volume, not surface area that matters.

>>4073921
That was funny.
Seriously. Thanks.

>>4073913
Not stupidity, everyone has to start somewhere.

The second question is easier to answer than the first, so I will start there.

Ice does not float because it is lighter, in fact it is technically incorrect to say that ice is lighter than water. What you mean to say is that it is less dense.

What this means is that if I had a bathtub full of ice and a bathtub full of water, the tub of ice would be lighter, even though the size of both tubs is the same.

When an object is placed in water, it pushes out (displaces) a certain amount of water equal to it's volume. As an example, fill a cup to the brim and stick your hand in it. Now if this displaced water is still in the container, it pushes back on the object. As it turns out, the force with which the water pushes on the object is equal to the weight of the water displaced.

So, go back to that tub of ice. If we dump the it in a large pool, the force on the ice will be equal to the weight of the WATER tub, which we decided was larger than the weight of the ice. Since we have a larger force pushing up, the ice floats.

This is the reason that anything floats in liquid. It is less dense than the liquid.

basically its because of these things called hydrogen bonds. When water is in a liquid form these bonds hold the water molecules close (relatively) together. However when it cools the hydrogen bonds re-arrange themselves so that the molecules are more spread out, hence why ice is less dense than liquid water.

http://en.wikipedia.org/wiki/Hydrogen_bonding

>>4073913
Also thought it was because water (H2O) have a specical attribute that makes the molecules most dense at +4 celsius. Which is why water doesnt freeze beneath the surface and also why there is life on earth.

>What is it about water that makes it expand when it's cold
The structure of the water molecule makes it form a crystal lattice that consists of water molecules that each has a double bond to adjacent water molecules (4 bonds in total for each molecule). This causes the water molecules to pack neatly into a crystal structure, but leaves "gaps" which could've been filled by other water molecules in less "ordered" conditions.
(see pic)

>am I right in thinking nothing else does this?
No.

>Secondly, as ice floats on water, this implies that ice is lighter than water? Is this just because it's expanded and so has a larger surface area? Or does it actually lose mass?

>lighter
Nope.
It's less dense than water.