Does Hot Water Freeze Faster Than Cold Water?

Hot water freezes faster than cold water, a phenomenon known as the Mpemba effect. The effect is named after a Tanzanian high school student who provided an interesting parable about this phenomenon in 1969.

The Mpemba effect depends on initial conditions.

Take two containers of water, one at 211 degrees Fahrenheit and the other at 33 F. In this case, the container with the 33 F water freezes first. If the initial conditions use water at 72 F and 100 F, however, then the Mpemba phenomenon takes effect and the water that was at 100 F freezes first.

Scientists are unsure of how this effect occurs, but the general explanation usually involves supercooling and convection currents.

The Mpemba effect derived its name from Erasto Mpemba, a Tanzanian student who discovered that a mixture of heated ice cream freezes more quickly than a cold ice cream mixture. A team of physicists from the Nanyang Technological University attributed this occurrence to the hydrogen bonding of water molecules that affects the covalent bonding between the hydrogen and oxygen atoms that comprise a single water molecule. The way energy is stored in these bonds in warm water allows it to release energy and freeze faster compared to cold water.