• When water freezes, it expands in volume as ice is formed.
  • The density of any liquid increases as its temperature decreases.
  • For most liquids, this continues as the liquid freezes and the solid state is denser than the liquid state.
  • However, water behaves differently.
  • It actually reaches its highest density at about 4°C.
  • Ice is less dense than liquid water and so it floats.
  • Since the ice does not sink, liquid water remains under the ice all winter long.
  • This is important, as fish and other organisms are capable of surviving through winter.
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