True or False: Cold water is denser than warm water.

Cold water is denser than warm water due to the molecular structure and behavior of water as its temperature changes. At lower temperatures, water molecules move more slowly and are packed closer together, resulting in a higher density. As water is heated, the molecules gain energy, move apart, and occupy a larger volume, which leads to lower density. This principle is fundamental in many environmental processes, including the stratification of water bodies where colder, denser water tends to sink below warmer, less dense water.

Understanding this concept is important in wastewater treatment, as temperature fluctuations can impact the efficiency of biological processes, chemical reactions, and the overall behavior of contaminants in water. The other options do not hold as universally applicable truths, as density changes with temperature are not limited to specific conditions like freezing points or saltwater scenarios.