What does all the water in a lake have to be cooled to 4 C before the surface water can be cooled below 4 C?

Question

Why does ice form at the surface of a body of water instead of at the bottom? Do most solids float on their liquid counterparts?

Why do islands surrounded by water not have the same temperature extremes that interiors of continents do? Why does the direction of prevailing wind change from day to night at the seashore?

Discuss at least one other example in which water’s properties are useful to people.

Answer 1

Everything condenses as it cools.

Condensing makes things heavier (more mass per unit volume.) The heavier water falls to the bottom while the lighter/warmer water rises to the surface.

Water is unique due to the fact that it is the only know material that expands when it freezes (changes state from a liquid to a solid.) This expansion makes ice (solid water) lighter than liquid water. Since the ice is lighter than liquid water, it floats (put an ice cube into water and see what happens.)