At which temperature does the maximum density of water occur?

• A. 0°C
• B. 4.0°C
• C. 10°C
• D. 20°C

Answer: (B)

Water reaches its maximum density at 4.0°C. This property is unique to water and is crucial in various natural and environmental processes. As water cools from higher temperatures, it becomes denser until it reaches 4.0°C. Below this temperature, water begins to expand, making it less dense. This unique behavior is responsible for phenomena such as the formation of ice, which floats on water, and the seasonal turnover of lakes.

In aquatic environments, the stratification of water layers occurs because warmer water is less dense than cooler water. Therefore, during the winter, ice forms on the surface of lakes rather than sinking, which insulates the water below and protects aquatic life during cold conditions. Recognizing that maximum density occurs at 4.0°C is essential for understanding these ecological dynamics and the physical properties of water.