describe the anomalous expansion of water?
413564
Water molecules participate in hydrogen bonding (H-bonds). The number of H-bonds formed in water increases with decreasing temperature. \n\nWhen the mocules freeze, this bonding causes them to align in a relatively ordered crystal lattice. The molecules could be closer together if it weren't for the H-bonds but with them, the lattice is the most stable configuration.\n\nAn ordered crystal lattice has more space in it than the molecules in liquid phase water, hence the expansion.
647764
Most of water's interesting physical characteristics can be traced to the nature of the hydrogen bonds that comprise it.  We tend to think of water as H2O a unitary molecule.  The reality is that the hydrogen bond is somewhat weak and you really have is more of a soup. \n\nThis behavior of water is so unique that people have mad careers of studying it.  Indeed it is said by some that if water did not exhibit the characteristics that it does life itself could not exist.
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.
549677
This is a chemistry question, the anomaly is due to Hydrogen bonding.
858544
Because water expands when it freezes..\nTherefore ice is of larger volume than the water it originated from\ntherefore it is less dense..
933014
All decent explanations so far; I hope I can add to what has already been posted.\n\nLiquid and Ice most definitely can exist at the same temperature and Ice can be and often does get colder than 0C.\n \nFirst of all the Triple Point of water is the pressure and temperature at which Ice, Liquid Water and Water Vapor exist at the same time in equilibrium.  Vapor is the right word, not steam although you can argue that the only time that Water Vapor and Steam are the same thing is at a very low pressure.  The Triple point of water only happens at a near perfect vacuum, 0.0063 ATM to be precise.\n\nAdding Salt to water will lower the freezing point, but then it isn't water anymore, it's salt water.  Even so, Liquid Salt Water and Ice Salt Water can also exist at the same place and time at the same temperature, slightly below 0C.  But let's stick to water.\n\nIce can easily be lower than 0 degrees.  Consider a bucket of water, liquid water sitting outside and the air temperature is -10C.  Little by Little, as the liquid reaches 0.0098 C, liquid starts to become ice.  The ice crystals form in the bucket, around the walls of the bucket and on the surface first.  The air is still -10C so the bucket, the liquid and the ice will keep getting colder.  The ice on the surface will drop to slightly below 0C but very slowly since it is still absorbing the heat of the not-yet-frozen water.  Eventually, the entire bucket of water will be frozen and will be just below 0C.  First the walls of the bucket will reach -10C (same as the air tempertaure).  The ice near the walls of the bucket and on the surface will reach -10C first, continually absorbing the heat energy from the relatively warmer ice near the center of the bucket.  Until finally, the entire bucket of ice is steady at -10C.  That is until the sun comes out or the day gets warmer.\n\n\nAnd by the Way, dry ice is not water, it's frozen CO2 (Carbon Dioxide)\n\nOne more thing, at a near perfect vacuum, you can actually cool liquid water to less than 0C without it freezing.  Never tried that but I did accidently freeze a beer last night...
131583
i would think that the radiation from the freqs listed above should all cause excite the water molecules in the same way but to differing extents. that's a very good question; i think i'll research it.
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.
798005
water has an anamalous behaviour. normally substances contract on cooling but water behavs in an opposite way meaning they expand on freezing\nat a very low temperature water freezes and expands.therefore the water pipes lines burst at very low temperatures. same with glass bottles containing water kept in a freezer explodes.\nhope that helps!!!
987678
Liquids have a definite volume but no definite shape, therefor only volume change occurs with change in temperature. But, liquids have to be in a container... so...\nwhen you heat them the contianer expands too. The real expansion = the apparrent expansion(what it looks like) after you allow for the expansion of the container.
1012439
Heat will make molecules expand.  Expanded molecules will take up more room and will affect the volume.  A hot liquid will take up more volume, especially in small containers, like pipettes.  It will give you a false measurement.\n\nFor accurate results, the glassware is calibrated with liquids at the specified temperatures.
277716
I think water is the only compound that expands when it freezes, everything else shrinks.
538394
This is a purely physical change of state from solid to liquid as a result of energy being added to the system.  There is an increase in entropy of the system.
304553
water becomes more disordered as it freezes which is why it expands. the second law of thermodynamics states that without an input of energy things tend toward disorder (entropy) or results in "anarchy" as the saying goes. as most liquids solidify they become more orderly and less random which is the exact opposite of what happens with water thus water defies one of many natural laws.
53531
Water expands when it freezes, possibly making the cube stick up.
36049
In hot water, it expands because the air molecule inside it move faster and it may pop. In cold water, it shrinks because the particles move slower. If u move it quickly from hot to cold water or vice-versa, it may pop too because of the severe change in temperature.
1018649
Water reaches a density maxima at 4C.