When hot water is thrown into extremely cold air (such as at temperatures below -30 degrees Celsius), it can freeze quickly due to a phenomenon known as the Mpemba effect. The Mpemba effect refers to the counterintuitive observation that hot water can sometimes freeze faster than cold water under certain conditions.
Several factors contribute to the rapid freezing of hot water in extremely cold conditions:
Increased surface area: When hot water is thrown into the air, it breaks up into tiny droplets or mist. The smaller droplet size increases the overall surface area of the water exposed to the cold air. This larger surface area promotes faster heat transfer from the water to the surrounding air, leading to rapid cooling.
Increased evaporation: Hot water has a higher vapor pressure compared to cold water. In extremely cold and dry conditions, the hot water droplets can evaporate rapidly due to the large temperature difference between the water and the surrounding air. This evaporation process requires energy, which is drawn from the water, causing it to cool down more quickly.
Leidenfrost effect: The Leidenfrost effect occurs when a liquid comes into contact with a surface significantly hotter than its boiling point. In this case, a thin layer of vapor forms between the liquid and the surface, creating an insulating barrier. When hot water is thrown into extremely cold air, the water droplets can undergo the Leidenfrost effect, forming a vapor layer that insulates the droplets from the cold air. This insulation slows down the cooling process and allows the water to stay in liquid form for a brief moment. However, as the droplets disperse and their surface area increases, the vapor layer becomes less effective, and the water rapidly cools and freezes.
It's important to note that the Mpemba effect is not always observed and is influenced by various factors such as initial temperature, volume of water, humidity, and other environmental conditions. The effect is more likely to be noticeable in extremely cold and dry environments where the evaporative cooling and increased surface area play a significant role.