Did you know that warm water freezes faster than cold water?

This is called the Mpemba effect. It is named after the Tanzanian student Erasto Mpemba, who noticed this effect in the 1960s.

There are various theories for this phenomenon. The most widely accepted theory is:

• The freezing process starts with small air bubbles. In cold water, which contains more air bubbles than warm water, a layer of ice forms at the edge of the water, against the ‘container,’ which acts as insulation and slows down the cooling of the water.
• In warm water, which contains fewer air bubbles, no insulating layer forms, allowing it to cool down faster and thus freeze sooner.

Photo by Michael Faes on Unsplash