Water reaches its maximum density at 4 degrees Celsius. The biological importance of this is that
- A. lakes freeze from the surface down, insulating the water below
- B. ice sinks to the bottom of lakes in winter
- C. water boils at a higher temperature than expected
- D. evaporation from the skin removes very little heat
Explanation
Water colder than 4 degrees becomes less dense and stays at the surface, so ice forms on top and acts as an insulating lid while liquid water below shelters fish and other life. If ice were denser than liquid water, lakes would freeze solid from the bottom up.
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