If heat rises why does ice form on the top of lakes and ponds?

Answer 1

it's called the anomaly of water, which tells you that water is the exception of the rule and something special.
Water is actually densest as a liquid at 4deg Celsius instead of being densest as a solid. Heat rises means that usually the same substance hot is less dense than colder.

Answer 2

In most substances the molecules in the solid are more densely packed than in the liquid. Thus the solid phase is denser than the liquid phase. By contrast, the density of ice at 0 degree celcius(0.917g/mL) is less than that of liquid water at 0degrees celcius(1.00g/mL), so ice floats on liquid water. The lower density of ice compared to water can be understood in terms of hydrogen bonding interactions between H2O molecules. In ice the H2O molecules assume an ordered open arrangement. This arrangement optimizes the hydrogen bonds to four other H2O molecules. When ice melts, the motions of the molecules cause the structure to collapse. The hydrogen bonding in the liquid is more random than in ice but is is strong enout to hold the molecules close together. Consequently liquid water has a more dense structure than ice, meaning that a given mass of water occupies a smaller volume than the same mass of ice.

The lower density of ice compared to liquid water affects life on earth. Because ice floats it covers the top of the water when a lake freezes in cold weather, thereby insulating the water below. If ice were more dense than water, ice forming on the top of a lake would sink to the bottom and the lake could freeze solid. Most aquatic life could not survive under these conditions.

Answer 3

In general, hot gas is less dense than cold gas. Since the hot gas is less dense, it will rise and rest above the cold gas. Ice is less dense than water. Since ice is less dense, it will rise and sit above the water. The fact that the ice is colder than the water, yet less dense is an interesting property of water that has to do with the configuration of the molecules.

Answer 4

Water is most dense at about 39 degrees F (4 degrees C). This special characteristic allows lakes to freeze on the surface rather than from the bottom up. Fish go dormant but don't freeze and die.

Answer 5

When water freezes it expands and floats.
At 4 degrees C water is at it's densest and the bottom of the ocean is always at 4 degrees C

Answer 6

As ice forms, its' molecular structure expands, making it less dense than water, and lighter, so that it floats on top.
This expansion is also what makes frozen pipes burst when the water in them freezes!

Answer 7

The water molecules are not as close in ice as water thus less dense

Answer 8

The saying is that hot air rises because the density of air decreases as temp increases. Heat transfers from warmer to cooler objects.

Answer 9

Ice is lighter than water