What is the temperature at which water reaches its greatest density?

Water reaches its greatest density at approximately 39°F (or 4°C). This property of water is vital for understanding various aquatic processes and ecosystem dynamics. At this temperature, water molecules are packed more closely together than at any other temperature in the liquid state, which contributes to water's unique behavior, including its ability to float as ice.

The significance of this temperature can be observed in natural bodies of water. As water cools from higher temperatures, it denser up to 39°F. Below this temperature, as water cools further, it begins to expand, which is why ice floats. This phenomenon has important ecological implications, such as allowing aquatic life to survive under the ice in winter months.

Understanding the temperature at which water is most dense is essential for water operators because it impacts water stratification, mixing patterns, and overall water quality management within lakes and reservoirs.