Hot water??????

Question

We all know that hot water rises, but if this is the case; why does water freeze on the surface and not at the bottom where all the cold (coldest) water should be?

Answer 1

Density of Ice is 0.9 and that of water is 1.0; so ice will actually float and once frozen, it keeps deeper layers of water insulated from further lowering the temperature.

Answer 2

If you're heating the water from below, convection currents will result due to hot water have a lower density than colder water and hence rising to the top. Water is a bad conductor and does not conduct heat.

In winter, the water at the surface is cooler than the water at the bottom. Being cooler, the surface water will sink. However at 4 degrees Celsius (a special property of water), its density is at the greatest. Hence the water that stays below is at 4 degrees Celsius and the fish and other life forms continues to swim in it.

Now the surface water continues to lowers until freezing point and then becomes ice while the water below remains water as 4 degrees.

Answer 3

Hot water rises because it has lower density that cold water - up to a point. Water has it's highest density at about 4 degrees C. Ice has a much lower density than water so it floats. When water cools down below 4 degrees, the coldest is at the top and this freezes. A short distance below, the water is at 4 degrees and fish can survive (provided there is a short distance below). If it wasn't for this phenomenon, life as we know it would not be possible.

Answer 4

The freezing is done at the layer that is in contact with the cold air.

Also, for freezing to start at the bottom would mean the higher levels would have to stay liquid while at freezing point due to the cold having to pass through them.

Water also has a strange property where it is densest at around 4 degrees, this leads to water cooler than that floating on top of the warmer layers.

And in answer to an earlier poster IT HAS NOTHING TO DO WITH WIND CHILL.

Water still freezes on the surface on days with no wind, if anything winds at a high enough speed to cause noticeable wind chill would be rippling the surface of the water and making it harder to freeze

Answer 5

Its true that hot water wil rise due to its lower density, but in the case of water, its solid form (i.e. ice) has a lower density than the liquid form thas why all the ice will be on the surface, you can try it by putting some ice cubes in cola drink...the ice cube will NEVER sink to the bottom. so even though the colder water will be near the bottom, even if ir forms ice, this ice will migrate to the surface and accumilate there and once a thick layer of ice is formed on the surface, it will help prevent the rest of the liquid from freezing also...Lakes in winter never completly FREEZE...only the surface...If ice had a higher density than water, all the lakes and rivers would have compltly froze in winter :)

Answer 6

Because of the difference in the two mediums. At the surface the water is in contact with cold air which is a gas and ultimately will freeze the surface water easier than the water at deeper sections

Answer 7

Hot water rises? Yeah Isn't it awful when you're boiling an egg and you leave it too long - all the water splashes around on the ceiling. Hmm.

Ice freezes on the surface because ice is less dense than liquid water. Its unusual in that respect to most substances. In benzene the solid form is more dense than the liquid and ice would form at the bottom and if you put a benzeneberg in liquid benzene it would sink to the bottom.

Answer 8

Water is strange when it freezes

By Jack Williams, USATODAY.com

Water is one of the essential elements that makes up the Earth's atmosphere and without it, Earth's weather would be much different. We'd have no clouds, rain, snow, sleet, hail, thunderstorms or hurricanes.

Water also is one of Earth's strangest substances, in that as water freezes, ice forms on its surface rather than on the bottom.

If water were like other substances, ice should form on the bottom of lakes and ponds because water would becomes more dense and sink as it cools.

The reason why ice forms on the top of lakes and ponds is that once water cools below 39 degrees Fahrenheit, it becomes lighter and less dense the more it cools.

This means that water expands as it freezes into ice.

As a result, ice takes up more room than the water it was made from. This makes ice lighter and less dense than the water below it, allowing ice to float on top of the water, rather than sink to the bottom.

This allows people to walk and skate on frozen lakes while fish are swimming below the ice. Ice can also cause problems if it forms in pipes. Since water expands as it freezes into ice, ice forming inside pipes can break them.

The next question, of course, is why does water grow less dense as it approaches the freezing point.

That gets a little complicated. To learn what happens, use the links below, starting with the first:

University of Alaska: Water as a solid citizen
U.S. Geological Survey: Water's chemical properties

Answer 9

Hot air rises, yes, but not necessarily hot water. I mean, it does rise, but it would expand all around more than specifically rising. The point is, the water acts as an insulator for itself. It sort of keeps itself warm, but at the top the air is colder than the water is, so it starts freezing there first.

Answer 10

The pressure of the water at the bottom of a lake or ocean would prevent ice crystals from expanding as they would on the surface.

Answer 11

Try this. Boiling or warm water Freezes faster than Cold water.