Aquatic organisms in lakes and ponds are often able to survive the winter underneath a layer of ice, because the water underneath the ice remains liquid. Which property of water is primarily responsible for creating these favorable conditions for aquatic life? Explain.

A. Water is an excellent solvent
B. Water has cohesive properties
C. Water expands when it freezes
D. Water has a high heat capacity

Most liquids tend to expand when temperatures increase, except water. In the case of water, temperatures below 4 ºC, the hydrogen bonds between the molecules of H2O become much stronger.

Once it gets cooler, the water starts to expand and eventually reaches the freezing point. This makes molecules to form a more stable and defined structure. This makes frozen water (ice) less dense than liquid water.

For example, ice cubes float in a glass of water because they are less dense than the liquid water.

Therefore, in ponds and lakes, ice tends to float over water. These bodies of water don't freeze completely because ice insulates the water below and creates a unique environment for aquatic species to survive and thrive even in cold seasons.