Final answer:
Ice floats on water due to its lower density, a result of the expanded molecular structure formed through hydrogen bonds. This prevents lakes from freezing bottom-up, protecting aquatic ecosystems during winter. The property of ice also has practical implications, such as in the use of antifreeze.
Step-by-step explanation:
Ice is less dense than liquid water, which explains why a layer of ice floats on the surface of a lake. This phenomenon is due to water's unique structure, including its shape, polarity, and the hydrogen bonding between its molecules. The lower density comes from the ice's expanded structure, allowing it to occupy more volume than the same mass of liquid water.
This characteristic is crucial for aquatic life during winter. If ice sank, lakes and ponds would freeze from the bottom up, proving lethal for ecosystems within. Instead, the floating ice provides an insulating layer, keeping the water underneath it in liquid form, and ensuring that fish and other organisms can survive the cold months. This anomaly of ice being less dense is a factor in many natural and man-made situations, from antifreeze usage in engines to the bursting of frozen pipes.
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.