What is the freezing point of water in degrees Celsius?

The temperature at which liquid water transforms into solid ice is a fundamental concept in science and everyday life. This crucial transition occurs at a precise point where water molecules, which are constantly moving in the liquid state, begin to slow down sufficiently to arrange themselves into a fixed, crystalline structure. This specific temperature marks the phase change from liquid to solid, a process vital for everything from weather patterns to preserving food.

This particular temperature was not arbitrarily chosen but is a cornerstone of the Celsius temperature scale. The Swedish astronomer Anders Celsius originally devised a scale in 1742 where 100 degrees represented the freezing point of water and 0 degrees its boiling point. However, this was later inverted, establishing the more intuitive scale we use today, where 0 degrees Celsius is the freezing point of pure water at standard atmospheric pressure, and 100 degrees Celsius is its boiling point.

While 0 degrees Celsius serves as the standard, it's important to note that this exact point can be influenced by various factors. For instance, the presence of dissolved substances, such as salt, will lower water's freezing point, a phenomenon known as freezing point depression. This is why oceans do not freeze solid at 0 degrees Celsius, and why salt is spread on icy roads to melt them. Pressure can also slightly alter this point; for water, increasing pressure actually causes the freezing point to decrease. This property makes the freezing point of water a fascinating example of how physical conditions affect the states of matter.