Hot and Cold Science

There’s an old saying that to make ice cubes freeze faster use boiling water in the tray rather than cold water as one might guess. Perhaps surprisingly, there might be some scientific truth to that…it’s called the Mpemba Effect.
The exact science behind this phenomenon is still being worked out and debated, however it raises some interesting questions. Last year Nature published a paper arguing that the Mpemba Effect doesn’t actually exist while another paper published earlier this year in the Journal of Modern Physics suggested that it does indeed exist, perhaps having to do with the structure of water collapsing when heated leading to more random collisions between molecules and thus faster cooling.

{If you’ve heard the old adage about the reverse phenomenon, that cold water will boil faster than hot water and are wondering if that’s true now, I’m sorry…that one has been proven false. Cold water does however bypass the hot water tank in your home and may taste better even if it takes longer to boil.}

But going back to the process of hot water freezing…
Another interesting phenomenon occurs when very hot water meets very cold air. Hot water contains more energy and has less structure (as explained by the above article in the Journal of Modern Physics). It’s actually closer to steam than cold water. So when it’s thrown into the air it breaks apart into tiny droplets each with a large surface area, facilitating the evaporation and freezing processes. Hot water thrown into cold air freezes almost instantly creating an impressive cloud of ice particles and fog. Try again with cold water and you’ll just end up with a puddle of ice on the ground.
Huffington Post published an article back in 2014 explaining this effect with some cool videos (www.huffingtonpost.com/boiling-water-extreme-cold-water-gun-ice). With the recent cold weather across the US I imagine there are lots of posts about this too.

This works best at temperatures below -40F and makes for some pretty cool photos. Unfortunately, we don’t have the bandwidth to upload videos here, so these pictures will have to do.

-90F at the South Pole on March 25, 2013:

South Pole March 2013

-50F at Summit Station on December 5, 2017:

 

-55F at Summit Station on December 1, 2016:

 

 

 

We also experimented with freezing bubbles. However, with no trees or mountains to break the wind it’s generally too windy for bubbles to last very long. It’s also been pretty cold lately at -75F last week so they freeze very quickly, often bursting.

 

If you’re looking for more fun science projects to do at home this winter check out this awesome post by NPR: www.npr.org/dont-just-shiver-here-are-3-cold-weather-experiments-to-try

And if you’re still interested in the science and history of cold check out the aptly titled, fascinating, and well written book: Cold by Bill Streever.