Question

Observation: You notice that a freshwater pond freezes over more easily than the ocean in the winter.

a) Ocean water has a higher freezing point due to salinity.

b) Freshwater has impurities that lower its freezing point.

c) The pond has a larger surface area than the ocean.

d) The observation is incorrect; ponds do not freeze more easily.

Answer 1

Ponds or lakes freeze at the surface because ice is less dense than liquid water.

Step-by-step explanation:

Ice is less dense than liquid water and so it floats. Ponds or lakes begin to freeze at the surface, closer to the cold air. A layer of ice forms, but does not sink as it would if water did not have this unique structure dictated by its shape, polarity, and hydrogen bonding. If the ice were to sink as it froze, entire lakes would freeze solid. 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. Ice is one of few solids that is less dense than its liquid form.