Why does ice form on the top of ponds and lakes, and not the bottom? How does this property of water help support life in lakes and ponds?
1 Answer
Ponds, lakes and oceans don't freeze solid every winter because water has a very unique property.
Explanation:
Water has a high specific heat . It takes a lot more than one degree of heat to raise the temperature of an amount of water by one degree.
If bodies of water froze solid in winter, life wouldn't be able to exist on Earth. In fact, if they froze solid, they probably wouldn't totally thaw by the end of the summer.
Water can absorb "a relatively large amount of heat", and its own temperature will only rise a little.
"The specific heat of a substance is defined as the amount of heat that must be absorbed or lost for 1 g[ram] of that substance to change its temperature by 1 [degree] C[elsius]."
In other words, water can absorb a lot of heat from the air, and its own temperature will only go up a little. And water can release a lot of heat to the air, and its own temperature will only go down a little.
"Compared with most other substances, water has an unusually high specific heat."
Also, "Floating ice becomes a barrier that protects the liquid water below from the colder air."
All quotes from Neil Campbell's college Biology textbook, third edition, pages 42-43. ISBN: 0-8053-1880-1.
Water is pretty cool stuff. I believe it's also the only substance that occurs naturally in 3 states: liquid, solid and gas (water vapor).
