Does cold water freeze faster than hot water?

2000/06/21 Elhuyar Zientzia

• Fisika

In general, cold water freezes faster than hot water, which seems more logical, but there are cases in which hot water freezes faster than cold water.

Suppose we have two containers full of water, in one container the water is 10 °C and in the other the water is 95 °C. Between them the water will be frozen at 10ºC. Let's take another example, we have again two containers filled with water, but this time the water is 50ºC and 95ºC respectively. In this case, even if it seems a lie, the hottest container water will freeze faster.

The explanation is simple, since to calculate the freezing speed of the water, several variables must be taken into account. In the examples cited, for example, the main variables are temperature and evaporation. At higher water temperature, higher evaporation and lower amount of water to freeze in the container. If the water to be frozen is less present in the container, the freezing will be faster.

This evaporation factor should be taken into account when we want to freeze very hot water and not always. In summary, it must be said that cold water freezes faster than hot water, but if the water is very hot it will freeze faster than hot water.