While most are not quite safe for kids, doing experiments is the most fun way of learning stuff. Getting that first-hand experience means you get to understand how things work and the visual will never dissipate. One such thing that you get to do is seeing how hot water freezes instantly in below freezing temperatures.
It is called the Mpemba effect, named after a Tanzanian student who discovered that a hot ice cream mix freezes faster than a cold mix in cookery classes in the early 1960s. Scientists were unable to explain the cause for this effect until recently. But first, let’s see what needs to be done.
First of all, you need to boil a solid amount of water. One pot will do. Next, you need freezing cold temperatures, like the ones that can only be found in Novosibirsk in Siberia, Russia. In this clip, the guy demonstrates that it is - 41 degrees Celsius, which is -41.8 Fahrenheit. Dressed in his nice, warm parka, the guy walks outside on his apartment balcony, his friend in tow to film the result.
Our scientist here grabs the pot of boiling water, takes one good look overboard to make sure no one is down to take the damage and tosses the hot load in the air.
If you thought that the water will turn cold and fall like rain, you are way off. This is where that strange Mpemba effect comes to play. To simplify it, hot water is less dense than cold water, so the molecules in water are further apart. When tossed in the air, it starts to evaporate faster, meaning small atoms get separated and they form ice crystals quicker.
Science aside, it is really cool to see a column of frozen water vapor form right outside your window. A cloud of you own, if you will.