A cold fact about hot water

With winter weather right around the corner, we thought you’d like this quirky water fact: In many cases, hot water will freeze faster than cold water.

Yes, you read that right.

There’s even a name for it: The Mpemba effect. The moniker comes from a Tanzanian student, Erasto Mpemba, who, while in a cooking class back in the 1960s, found that a hot ice cream mix froze faster than a cold mix.

Apparently, it’s a head-scratcher that’s puzzled scientists for centuries, dating back to Aristotle. Now, however, there may finally be an answer: According to an article on MSN.com, scientists at Nanyang Technological University in Singapore say it’s because “the way water molecules store and release energy varies with the initial state of water, with hot water releasing its energy faster when put into a freezer.”

What, exactly, does that mean? As you probably know, a molecule of water is made up of one oxygen atom and two hydrogen atoms. Xi Zhang, the scientist who lead the team, says that as the temperature rises, the hydrogen atoms stretch, pushing the water molecules farther away from each other. While it may seem like a contradiction, this allows warm water to cool faster than cold water, because energy can escape more quickly because of the wider span between the molecules.

If you’re still baffled, don’t worry — you’re not alone.  As we mentioned earlier, scientists have been puzzling over this question since about 350 B.C. If you want to see the effect for yourself, try it at home: fill one ice cube tray with warm water, and one with cold, and see which freezes first. You can let us know the results on our Facebook page.

Note: Never use hot water straight from your tap to fill ice cube trays. In fact, you should never use hot water from your tap for drinking or cooking. Hot water can contain higher levels of lead. Instead, heat cold water in a pan on the stove.

In fact, it’s probably not a good idea to regularly fill your ice cube trays with hot or warm water. Although it might freeze faster, the excess heat will make your freezer work harder.