Opening a Soda on the Ocean Floor

Chris Hadfield is among the best of us.

He's a fickin' astronaut, a pretty nifty quitar player, a hell of a pilot, a great science communicator, the father of an interesting YouTuber, and a good sport.

In this video, Chris doesn't do a lick of science explaining, but he does demonstrate the fact that if you're going to shake up a soda can and immediately open it, you'd best be under double atmospheric pressure at the bottom of the ocean.

To fill in what Chris doesn't explain, the fizzing is largely a result of this equilibrium...

H₂CO_{3 (aq)}  ⇌   H₂O _(l) + CO_{2 (g)}

At normal atmospheric pressure that CO₂ pressure is low, so the reaction shifts to the right until it reaches equilibrium and your pop is flat. Allowing the pressure to build up in a sealed container - keeping the coke bottle closed up - stops this from progressing because eventually Q = K. So does cooling down the tonic container because the reaction is exothermic and endothermic reactions (the reverse reaction, keeping the gas dissolved in the solution as carbonic acid) are favored at colder temperatures.

But at the bottom of the ocean, there's apparently a high enough CO₂ pressure in the atmosphere that the soda doesn't immediately fizz up.

Liquid Crystals Painted On Heat Pipes

So much science...phase changes due to pressure and temperature changes...constructive and destructive interference colors...thermal expansion made visible via liquid crystals...

I feel like I need to get me some of those heat pipes.

Can You Stop Water From Expanding When It Freezes Into Ice?

Chris Dyer graduated from Princeton in the spring of 2004 and died in Iraq in 2005.

I mention this because I remember doing this demonstration with Chris and his dad in the side yard of the old Princeton High School building. The AP chemistry students that year had seen an 'ice bomb' sold by Flinn Scientific. The thing they were selling was nothing more than an elbow of steel pipe with two screw caps. As the water freezes in the pipe, the water expands and eventually causes the pipe to explode.

I told the students we couldn't do that because I didn't have access to dry ice. I didn't mind spending the $20 or so (Flinn no longer sells that item, so I can't check the actual price) on the pipe, but I didn't have the dry ice or liquid nitrogen necessary to freeze the water inside it.

Chris piped (sorry) up that his father worked at a lab and had easy access to dry ice. So I ordered the pipe. John Dyer took the day off and came to school with his son.

And we blew up a pipe in the side yard.

Stupidly - because it was less fun to see - we blew it up inside a 3/4" plywood box. Smartly - because nobody got hurt and I got to keep my job - we blew it up inside a 3/4" plywood box.

That's my lasting memory of Chris Dyer.

And I'm really glad that The Action Lab guy moved his safety shield in front of himself and his camera just in time. I was worried throughout the first part of the video.

(Sorry for this being a bit of a downer post. Feel free to make a donation to the Chris Dyer Memorial Scholarship fund - either of them.)

Cocoa Powder That Can't Get Wet in Milk

We do this experiment in honors chem at Princeton HS when we study intermolecular forces.

The general response that I get from most students the first time they do the experiment successfully is general grossness and stunned. The peeling of the 'skin' of the cocoa is just so gross.

We, admittedly, don't do the demo with the lycopodium powder, but we might be doing that in the future. We do something similar to that with Magic Sand, though.

And we certainly don't do the demo with the vacuum pump. I have a vacuum pump, though. Interesting. Might be worth trying in the future.

And the flammable water at the end...hmmm...