why water(ice) becomes less dense n expand?


when water becomes ice, it comes less dense and expand ...very opposite if compared to other substance ..

if ice is denser than water, we wount hv iceberg ..

why is that ?

http://www.squidoo.com/water-Molecule-2

from wad i understand when water in freezing process, it gives off heat, thus pushing the molecules outwards..tada! expand. and also less dense.

because below 4 celcius the bonding between the molecules changed and causing the ice to take a more open crystal structure aka more spaces in between causing less dense lu~

Agree when water freeze, they become well arranged in a crystal lattice, while the molecules rearrange, they actually become more spaced between each other.

When water becomes ice,the structure looks like below:



It is a tetrahedral structure with lots of empty space between each tetrahedral unit(i think).This structure is the reason why ice floats on water,due to the fact that it is less dense.

When ice melts,some of these (hydrogen) bonds are broken,making the water molecule free to move around.At the same time,the voids between the tetrahedral structure is filled with bits of free moving water molecule.Think something like the structure in the picture above collapse.

The volume shrinks because the water molecules now occupy the empty spaces between the the ice molecule.At the same time,we know that density is inversely proportional to volume,hence,the density of water increased from ice.

Do correct me if im wrong.

Cheers.

This post has been edited by Cheesenium: Nov 2 2009, 07:46 PM

Eh? No lah that's not how it works.

Yeah you're right on most part, but if my memory recalls, it's not covalent bond, but the hydrogen bonds.
Covalent bonds are very strong and separable only by chemical reactions.

Instead, the oxygen atom in H2O are highly electronegative. Hence, there exists a weaker bond called Hydrogen Bonds.
It is that these bonds weaken, not covalent bonds.

Yeah,you are right.

It's hydrogen bond.Not covalent.

Yes i remembered something about Hydrogen bond too. Water is a very interesting molecule.

This post has been edited by soul2soul: Nov 6 2009, 04:24 PM

that is power of nature
imagine that iceberg below the sea???
every whole ecosystem will die.
bte it happend because water is H2O
hydrogen bonding

tis was wat we learn in physics durin old scl time
hav to do wit hydrogen bond n surface tension
forget liao~~

that's a special invention of the super-natural force.
if water without tis speciality then fish cant survive in the winter and we can walk on the ice.

Cheesenium, density will not determine if you float on water. Its bouyance that explains floating on water. Ships are more dense than water but they float.

thumbs up to dis answer

buoyancy is more or less related to density; for buoyancy, an upward force equivalent to the mass of displaced water pushes the object up. for material of higher density, you would need to displace more water compared to lower density material.

eg, you can make a fine raft out of wood, but not out of metal. while metal is denser than water, i would suspect (could be wrong, not sure) that the density of a ship (mass of ship/volume of ship) is less than water.

Hi Lim00b,

I am not that good in science. I only know everything has buoyancy. If it has buoyancy it will float. Are you saying buoyancy is the upward force the object up? Where did this force come from?

Water displacement.

The lifting force of the ship in the water is depended how much water displacement, so the larger the ship area that displaces the water, the larger the force is.

You mean the forces come from the water, Cherroy?

Yes, the large hulls of ship create a larger surface area thus reducing the force per area onto water. Thus reducing the apparent density

buoyancy force = rho(density) * V(volume of liquid) * g(gravitational acceleration)

oh.. so manny scientist term im blur about it, anyway, what i know is, ice is beoming less and less...