ice floats on water because ice is less dense than water, how is this helpful to fish tnat live in a lake

The helps fish in 2 ways. Since water can have a high amount of energy gained or loss and not change, the entire lake will not freeze. Thus, fish will still be able to live in liquid water. The ice also, as strange as it may sound, provide insulation for the fish, so they don’t freeze. The water can do this because it requires a huge change in energy to counteract the hydrogen bonds.

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