explain why water is most dense at 4c ?
546089
This must be when the particles are allowed to come into closest contact so give it its highest  density
208900
Specific gravity.\n\nPure water has a density of 1 (the mass of 1 cubic centimetre of pure water is precisely 1 gramme), if something was twice as heavy as water (i.e. it has twice the mass) it would have a specific gravity of 2, 6 times as heavy and the SG would be 6.  If something was half as light as water it's SG would be 0.5 and so on.
583824
ice has less density than water.  the H2O bonds in ice are in a crystal lattice structure and there are small bits of air trapped between them.
260171
It isn't air! When water freezes all dissolved gases & other matter are not included!!! \n\nThe hydrogen bonds that form when water freezes creates an open structure. There is simply nothing in between those spaces.\n\nWe are talking about molecular structure, things at this level are so tiny that even thinking about what is in between is silly.\n\nIf there is anything between the spaces it is probably interstitial water molecules (those not hydrogen bonded inside the crystalline lattice structure - think of them as loose molecules of water).\n\nIce floats on water because it has expanded. That is all. Not because of what is in between the "spaces".\n\nSee, when you increase the surface area but have the same number of molecules present, you cause the object to become less dense. (it's less tightly packed...things that are tightly packed for their size are said to be more dense.)
279658
Ice floats on water because it is less dense than water, meaning it has fewer molecules per volume. This is because of the Hydrogen bonds. In fact, while other substances contract when solidified, water expands. That's why it's less dense, and not because it has air inside. Furthermore, when the temperature decreases and reaches 4 degrees Celsius, every water molecule is Hydrogen-bonded to 4 other molecules near it. Then, they form into a crystal lattice structure, and it holds them further apart.
314279
The reason that water expands upon freezing is because of the strong hydrogen bonding between the water molecules. Water is polar having a positive end nearest the Hydrogens and a negative end nearest the Oxygen atom. Therefore The positive ends of some water molecules attract the negative ends of other water molecules. When water reaches 4 degrees Celsius the molecules have been pushed as close to one another as they will be. Below 4 degrees the water molecules begin to align themselves into the crystal structure of ice. This requires the water molecules to widen the angle between the Oxygen Hydrogen single bonds . When this happens the water molecules take up more space hence expansion.
873711
Not quite right.  It is most dense at 4 degrees C.  If it didn't, the water would freeze from the bottom up.  As it approaches 0 degrees, it becomes less dense and rises above the more dense warmer water and freezes on the surface and goes down.  Otherwise, fish would be on top of the ice and die after it froze.
875269
The density is different - sea water being more dense than fresh.\n\nFreezing point (lower for sea water) and boiling point (higher for sea water) would be slightly different.\n\nElectrical conductivity would be different (higher for sea water).\n\nAll these things are different - but the differences are also all due to the salinity difference that you mentioned.
68685
water with salt bcoz water bcoms lighter wen alt dissolves in it ans hence its density decreases allowing it to evaporate easily
480166
If you have an equal volume of hot and cold water the cold water will be heavier.  This is because when you heat up a substance it become less dense, and in general when you cool down a substance it becomes more dense.\n\nThe exception to the rule is water though.  Water is most dense at 3 degrees cesius, after that it start to take a crystalin form and when it freezes actualy expands.  \n\nso long as you are not saying that the cold water is 1 degree and the hot water is 3, then the cold water will be heavier\n\n\nBut remeber it is not by much in any case
524116
Thanks to the wonderful nature of the water molecule, ice is the only product in nature that actually expands as it cools. Once water gets to be less than 4 degrees C, its crystalline nature takes over and the molecules start to line up and push each other apart. This is why ice floats on water. The colder the ice, the less dense it becomes, the higher it floats. EXPERIMENT: Take a thin glass and fill it halfway with water. Mark the level of the water with a grease pencil. Put the glass in a cold refrigerator. The water level will go down. Now put the same glass in the freezer overnight. The water level will go up. The colder the freezer, the higher it will go.
858544
Because water expands when it freezes..\nTherefore ice is of larger volume than the water it originated from\ntherefore it is less dense..
502816
Particles in solids are usually packed closer together than in a liquid. But in the case of water, the presence of hydrogen bonds holds water molecules apart in an open lattice structure, as in a tetrahedral open lattice. \n\nAs water cools, it contracts and hydrogen bonds are formed in greater quantities. Since hydrogen bonds are long and strong, they space the water molecules so that the volume of water increases, thereby decreasing its density (when water freezes, it expands by 9%)\nThe hydrogen bonds in solid ice hold the molecules together in fixed positions, revealing a large proportion of empty space. Since it has low density, ice shows the unique property of floating. But in liquid water, hydrogen bonds are constantly being made and broken.
192094
um. well i would assume itz cuz some of it has a lower density than water and some has a higher density? lower density meanz more holes and stuff in it and higher density means   packed more tightly? hahah. why do you care?
267364
Fresh water has its greatest density at 4°C, then becoming less dense as it freezes or heats up from this point.
180387
heavy water is about 10% heavier then regular water.  \n\nDensity of heavy water = 1.1056 g/ml \nDensity of regular water = 0.9982 g/ml\n\nYou can calculate the conversions to gallons.\n\nAnd oh yah that earlier guy is an idiot.  Heavy Water is not radioactive.  It is a stable molecule that is used in nuclear reactors.  B/c of its greater density it is perfect for the control of nuclear reactions.
196823
The fact that ice always floats on water should give you a clue!  The ice is obviously not as dense.  So you can infer from this something has happened during the freezing process.\n\nThe structure of a water molecule is One atom of hydrogen to two if oxygen.  As the water freezes hydrogen bonds form between the various water molecules and these stop the molecules packing as effectively so the ice is less dense.\n\nTry the source below.