I Am Guessing Many Of Us Will Have Seen This,

throw boiling water into the air and it freezes, faster than it would if you used cold water!

photograph YouTube, well it does pay to plan the event, Jiang Nu travelled with her boyfriend to Northeastern China’s Heilongjiang Province and, one night, she grabbed an electric kettle full of hot water, stepped out into the cold, and had her partner record her while she attempted a popular trick she had seen online, alas although it was -20 degrees Celsius outside as she flung the kettle in a circular pattern, as she was supposed to in order to get the desired effect, the hot water didn’t freeze, instead, some of it landed on her exposed head,

Her boyfriend rushed to help her and later took her to a local hospital for treatment. Luckily, Jiang was smart enough to apply a cold compress to her head to prevent further damage, but she still suffered second-degree burns, so the very next night, Jiang Nu attempted the hot-water-to-ice trick again. However, this time around she wore a thick hood to protect her head, so even though she failed again, she didn’t suffer any more burns, back to the first night, a few stills,

kettle in hand, 

the boiling water went up, 

and then down, Mr. Gravity at work, the effect of boiling water freezing before cold water is called The Mpemba Effect, a bit of a long post but here it is:

In 1963, a Tanzanian schoolboy Erasto Bartholomeo Mpemba was doing a simple school physics experiment and discovered that hot water freezes faster than cold water.

This seems impossible because logically you’d say that as the hot water cools, it would take some amount of time to reach the same temperature as the cold water - and from that moment, take the same time as the cold water did. Therefore, you’d argue, there is no way for the hot water to freeze faster.

But Mpemba very definitely found that hot water freezes faster than cold water IN SOME CIRCUMSTANCES.

His odd finding was initially ignored - but a few years later, Mpemba asked a visiting physicist (Dr Denis Osborne) in question time after a lecture - and while everyone (students and teachers) in the classroom laughed at him, Osborne actually took him seriously - tried to repeat the experiment and found that Mpemba was correct!

Osborne and Mpemba collaborated to write a paper - which was published in Physics Education, Volume 4, Issue 3, pp. 172-175 (1969). The paper goes a little deeper into the problem and eliminates the two most common explanations (dissolved air and evaporation).

It turns out that there are a huge range of subtle effects going on here - and it’s not ALWAYS the case that the hot water freezes first - it’s sensitive to initial conditions…but if you follow the steps in the paper, it is quite repeatable.

However, the reason for this weird behavior had sparked off complicated discussions and there are at least ten alternative explanations - and to this day, no single one of those possible explanations are the single, widely accepted, cause.

There is a related paradoxical claim - the “inverse Mpemba” in which heating warm water to a specific temperature can take more time than heating cold water to that exact same temperature.

The best answer to both phenomena seems to be “Water Is Complicated!”