Science fun in the Big Freeze

The UK is currently in the grip of the longest period of sub-zero weather in thirty years, and it looks set to stay cold for another week. Rather than get hysterical about the lack of grit on our roads, I thought about all the fun science opportunities the arctic weather has on offer!

Supercooling
Everyone knows that water freezes at zero degrees celsius, but not many people know that ice crystals need a small imperfection or "seed" to grow from. This can be impurities in the water or microscopic imperfections in the container holding them. Without these, water will stay liquid well below freezing temperatures, in a supercool state. The tiniest disturbance will then cause all the liquid to freeze instantly! You can replicate this with a bottle of purified water (e.g. Dasani) left outside overnight.

Frozen Bubbles
Everyone loves blowing soap bubbles, but even more fun is blowing them in sub-zero conditions, where the bubbles will freeze as fast as you can blow them and then roll along the ground!

Weather Modification
Take a cup of hot water. Throw hot water at the sky. Instant snow! Feel like China.

Which freezes faster?
Finally answer that long standing question: which freezes faster, hot water or cold water? A fun way to demonstrate the Mpemba Effect.

Add your suggestions of science fun to have in the big freeze below!

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Fun stuff.

The Mpemba Effect reminds me of when I was told once (back in undergraduate days) that cold water will boil fast than hot (tap) water. It seemed to me (and still does) that this must be false because as you heat the cold water it will after a period of time be indistinguishable from the hot (tap) water -- and from that point on will take the same amount of time to come to a boil.

I'm tempted to say that I'm assuming that the process should be Markovian (but I'm not saying it at the moment).

Maybe tonight I'll go empiricist and pull out a pot and a stopwatch . . .

By Physicalist (not verified) on 11 Jan 2010 #permalink

Empirical results:

A liter of hot tap water boils in five minutes.
A liter of cold tap water boils in seven.
Null hypothesis confirmed.

And it turns out a watched pot does boil.

(Experimental arrangement not as controlled or precise as one might like, but it's a start . . . )

By Physicalist (not verified) on 14 Jan 2010 #permalink

I've heard that before. I think its an urban legend that arose because cold water will start to bubble sooner due to more dissolved gasses.