jtotheizzoe: Pop Goes The Dry Ice Bubbles! I’m giving you a...

jtotheizzoe:

Pop Goes The Dry Ice Bubbles!

I’m giving you a challenge at the end of this post, so stay with me. It’s a fun lesson!

First off, if you don’t follow Brusspup’s awesome science illusions, I highly recommend checking them out. Here’s his “best of” for 2012. It truly boggles the mind.

Look at the size of those dry ice bubbles! There is some awesome, and yet simple chemistry at work here. Most people are familiar with dry ice vapor: It’s frozen carbon dioxide turning into gas (and taking some frozen water vapor with it, which is why it’s white) when it’s placed in a bowl of warm water. Seen it a million times, right?

Then he uses a soap bubble to hold the vapor in the bowl, increasing the pressure until we get an explosion of sinking, heavier-than-air carbon dioxide vapor. Whoooooosh. But why does that work? What are bubbles anyway?

Soap molecules have two ends, one that likes water (it’s “hydrophilic”) and one that doesn’t (“hydrophobic”). This is why we use soap to clean greasy things using water, because it can stick to both, in a sense. The soap molecules actually trap the water in a thin layer, creating a film like this:

Soap bubbles are nothing more than thin layers of water held prisoner by soap! Mean old soap. As a force (like putting vapor inside) is added, the soap film wants to find the shape with the least surface area per volume, which happens to be a sphere.

The glycerin, a very thick and viscous hydrophilic molecule, helps make the water layer a bit more sticky so the bubble can get bigger before becoming unstable. Eventually the force of the vapor pressure is too much for the intermolecular stickiness of the soap film, and the soap layer rips apart, popping the bubble.

This is a pretty easy experiment to do at home. Think you can make a bigger bubble? Yes, that is a challenge. It’s your mission, should you choose to accept it.