Answer :
Water is most dense at 4 degrees Celsius.
The density of water changes with temperature because the water molecules move closer together or further apart as temperature changes. At temperatures above 4 degrees Celsius, the water molecules spread apart more and become less dense as the temperature increases. Below 4 degrees Celsius, ice starts to form which also makes the water less dense because ice is less dense than liquid water, causing it to float.
Understanding the density of water is important in various scientific fields, such as environmental science and biology, because it affects aquatic life and ecosystems. For example, the fact that ice is less dense than liquid water allows ice to float on the surface of ponds and lakes, providing insulation and protecting aquatic life during winter.
Therefore, the correct answer is option 3: 4 degrees Celsius.
