Question

In einter the upper surface of the lake water freezes but the the inner surface remains water. Why?

Answer 1

There are two reasons why. (1) The air is the source of the cold, and the earth below retains warmth better. Thus, the surface is frozen, while underneath it is heated (or kept from freezing) from below. (2)Ice is less dense than liquid water, and when a solid crust of ice is on a lake, the water underneath is under pressure. The freezing point drops with increasing pressure for a substance the liquid of which is denser than the solid