The Mpemba effect describes the phenomenon that hot water may freeze faster than cold. To precisely state what is Mpemba impact, begin with two containers of water, same in shape, and with same amounts of water. The only difference is the water temperature one is at a higher temperature than the water in the other. cool two containers, using the exact same cooling process for both containers. In some conditions at first warmer water will freeze first. It means the Mpemba effect happens. Here's the proof. Say that it takes 10 minutes to freeze the initially cooler water starts at 30°C , while the initially warmer water starts out at 70°C. Now the initially warmer water needs more cooling time to get to get down to 30°C, then it needs 10 more minutes to freeze. So since the initially warmer water has to do everything that the initially cooler water has to do, plus a little more, it will take at least a little longer. Somehow, the hot water must be able to lose its heat faster than the cold water.
Evaporation- Theoretical calculations have shown that evaporation can explain the Mpemba effect if you assume that the water loses heat solely through evaporation . When the initially warmer water cools to the initial temperature of the initially cooler water, it may lose significant amounts of water to evaporation. The reduced mass will make it easier for the water to cool and freeze. Then the initially warmer water can freeze before the initially cooler water, but will make less ice.
Convection- Water density usually decreases as temperature increases, so a container of cooling water typically is warmer on top than on the bottom. If we assume water loses most of its heat across its surface. As the water cools it will eventually develop convection currents and a non-uniform temperature distribution.
Conduction- Without mass movement of matter heat transferred by direct molecular interactions,. For example, a hot water in a container, the container soon feels warm. The water molecules colliding with the inside surface of the container transfer energy to the container, warming it up.
Surroundings- The cooling of the two containers relates not to the water itself, but to the surrounding environment. The initially warmer water may change the environment around it in some complex fashion, and thus affect the cooling process. surroundings that could influence the rate of cooling. One example would be warm water melting a pre-existing layer of frost, permitting a better cooling rate.
Dissolved gasses- Hot water can hold dissolved gases than cold water, which may affect its rate of freezing.
Supercooling- that the initially warmer water might freeze first because it would freeze at a higher temperature than the initially cooler water. It happens when when the water freezes not at 0°C, but at some lower temperature. One experiment found that its initially hot water supercooled less than its initially cold water.
It is not impossible that hot water does freeze faster than cold water in most circumstances. It is not impossible, and has been seen to occur in some experiments. In order to understand how this could happen: