Q: Why are these bubbles flammable?
Why study chemistry: you can light your hand on fire.
Well, sort of. You can at least light these special bubbles on fire. This demo relies on the combustion of methane.
I’ve written about combustion before, but to recap: combustion is an exothermic chemical reaction in which fuel reacts with oxygen to produce heat and exhaust.
In this demonstration, methane (CH4) is the combustible fuel. Methane is a colorless and odorless gas that is easily ignited. The methane reacts with oxygen, and carbon dioxide and water are created.
Methane gas is pumped into soapy water, forming methane-filled bubbles. (The methane could be pumped in directly from a methane gas cylinder, but like science outreach performer Steve Spangler, my groups tend to fill inflatable pool toys with methane gas in order to transport the gas to demonstration show locations. We then attach a tube to the opening of the inflatable toy and place the tube’s other end in the soapy water. Squeezing the toy forces the methane out of the toy and into the soapy water, forming bubbles.)
The demonstrator then coats their hands with soapy water. This allows them to pick up the bubbles without the bubbles popping. It also gives a layer of protection from the eventual heat and flames.
The demonstrator can then scoop up the methane bubbles and light the bubbles on fire, creating a large flame. Their hands are protected by the layer of soapy water. Instead of ending up with a burned hand, the water takes on the heat and evaporates away.
Please don’t do this at home. It’s a lot of fun, but that’s why you should study chemistry- so you can become a trained demonstrator and do really cool activities like this.
Keep calm and science on.