What happens to water when it reaches 0 degrees Celsius?

When water reaches 0 degrees Celsius, it is at the freezing point, but it does not mean that it will automatically turn into ice. At 0 degrees Celsius, water can exist as a liquid in a supercooled condition, especially under certain conditions. Supercooled water occurs when water is cooled below its freezing point without it turning into ice, often happening in pure, undisturbed water in a clean environment. This means that it can remain liquid even at this temperature until it is disturbed or has something to initiate the freezing process.

The notion of water instantly freezing is a common misconception; in reality, the process can depend on various factors such as impurities, pressure, and the presence of nucleation sites, which can trigger the formation of ice if they are present. Thus, the property of water at 0 degrees Celsius allows for the existence of a liquid state under specific conditions, making the understanding of supercooling essential in comprehending water's behavior at its freezing point.