why density of ice is less than water even though it is in solid state?

Answer 1

"others will give a much more enlightened answer, but...water is the only element that expands when it freezes."

THIS IS NOT TRUE

Bismuth also expands as it freezes.

Water and bismith crystallize when frozen.

Answer 2

Because when water freezes it forms a cage like structure, in which much space is there inside. So it is some how expanded. As the volume is more but mass will be same hence it acquires less density and floats over water. Sometimes gases are being trapped in these cages and it is of much research interested by scientists that they get it from ice cores and analyse them to know what will be the atmospheric condition when the polar ice has been formed.

Answer 3

It is due to the anomalous expansion of water. That is wates shows an unusual property when heated from 0 degree celcius to 4 degree celsius or cooled from 4degree celcius to 0 degree celcius when heated from 0 c to 4 c the water contracts instead of expanding. This means that the volume decreases & density increases. When water is cooled from 4c to 0c it expands instead of contracting .This means that the volume of water increases & the density decreases.

Ice is formed at 0c. Hence ice at 0c has less density than 4c of water. That is why ice floats on water even though it is in solid state.

Answer 4

Hydrogen Bonding.

The phenomenon of hydrogen bonding explains most of the unusual properties of water (very high melting and boiling point for a small molecule, lower density in crystalline form, etc.). In a nutshell, hydrogen bonding is a type of intermolecular interaction that can occur in polar molecules, such as water and alcohols. It is the "bond" formed between the H atoms of one molecule and the O atom of another. Note that this is not as strong as the intra-molecular bonds, but nevertheless, it is much stronger than any other type of intermolecular interaction. This basically means that the water atoms in a liquid are very tightly bound through a network of hydrogen bonds, but in the solid, those bonds must be broken in order to form the crystalline structures of ice.

Water has the most hydrogen bonding of any molecule because it is so small that its electron density is easily polarized (electrons prefer to be near the O atom, and away from the H atoms).

Answer 5

Most materials tend to expand when heated and contract when cooled. By logic, ice should therefore be denser than liquid water.

The reason ice is less dense than liquid water is that, unlike many other materials, water crystallizes when it freezes, rather than just condensing into a lump. This crystal is less dense than liquid water.

Also, I believe that if you freeze ice at a very low temperature (say, about 100 kelvin), it can become solid without going into a crystal formation and actually be denser than liquid water. But conditions like that don't exist naturally on Earth, so we aren't used to dealing with this kind of ice.

Answer 6

Most molecules are connected in straight lines, but because of the odd nature of water (it shares electrons between its hydrogen and oxygen atoms) it is bent at an obtuse angle. For this reason, it develops a partial charge, negative on the oxygen side and positive on the hydrogen side.

When water freezes, the molecules line up in a crystalline structure, but because of the odd shape of the molecule and that partial, it can't fit tightly together. It actually can pack better as water, because the molecules are all twisted about and can fit into each other's gaps.

Hold your first finger apart in a sort of U shape and see how you can put the finger of one hand in the gap between the finger and thumb of the other hand and get the two hands quite close together without having them touch. Then turn one hand around so that the thumb/finger of one is pointing at the back of the other hand. You can't get them to pack in now. That's how water works when it's crystalline as well.

Answer 7

Water volume expands at 4 deg. C. That larger volume for the given mass results in lesser density. That is why ice float in water.

Answer 8

While change of state, instead of coming closer, the space between water molecules expands.So, the number of molecules per unit volume(the density of molecules) decreases.The density of water is highest at 4 degree celsius.But at this temperature, it is liquid in state.

Answer 9

this is called the anamolous behaviour of water. water, when cooled from 4C to 0C expands instead of contracting. volume is inversely proportional to the density. therfore, when the volume increases, the density decreases. thus the ice formed is less denser than water and therefore floats on water

Answer 10

water crystallizes when it freezes and this crystalline structure actually is less dense than liquid water. When liquid water is cooled, it contracts like one would expect until a temperature of approximately 4 degrees Celsius is reached. this si the point of maximum density of water. After that, it expands slightly until it reaches the freezing point, and then when it freezes it expands by approximately 9%. The water molecules almost 'pop' into an expaned crystaline structure at 0C. ( assuming there is a nucleation site for the crystals to form.. pure water can remain liquid until lower temps if there is no nucleation site)

The expansion upon freezing comes from the fact that water crystallizes into an open hexagonal form. This hexagonal lattice contains more space than the liquid state.


~~~~~~~~~FYI~~~~~ EDIT ~~~~~~~ FYI~~~~~~~~
Everyday ice is a crystal, which means its molecules are lined up in a repeating pattern. Amorphous ice is an amorphous solid form of water, meaning it consists of water molecules that are randomly oriented like the atoms of common glass. Amorphous ice is produced by cooling liquid water very quickly (around 1,000,000 K/s), so the molecules don't have enough time to form a crystal lattice.

High-density amorphous ice (HDA) can be formed by compressing ice Ih at temperatures below ~140K. At 77 K, HDA forms from ordinary natural ice at around 1.6 GPa[3] and from LDA at around 0.5 GPa[4] (atmospheric pressure at sea level is about 0.1 MPa), and has a density of 1.17 g/cm³ when recovered back to ambient pressure. The resulting collapsed structure resists reverting to LDA at lower pressures and is stable for months at 77 K and 0.1 MPa.

Very-high-density amorphous ice (VHDA), discovered in 2001 at the University of Innsbruck,[5] is usually made from high-density amorphous ice at 77 K by heating it up to about 160 K while under pressures of ca. 1-2 GPa to create an annealing process. Once formed VHDA is more stable than either HDA or LDA and can retain its structure for years at normal atmospheric pressure. It has a density of 1.26 g/cm³.

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

Answer 11

Water is held together by hydrogen bonds between the oxygen in one molecule and hydrogens in other molecules (it is a polar molecule which means that there is a more negative side by the oxygen, and a more positive side by the hydrogens). When water freezes, these hydrogen bonds are broken, and so the molecules are not held together as tightly. This is responsible for the expansion when freezing.

Hope that clears things up a bit. :)