Carbon Snakes

Here's a project I neglected to post last spring. We weren't totally satisfied with the results, so it never made it into the blog. Just this week, however, I found something fun to add, so I'm putting it up now for the record.

This experiment, like so many we did last year, came from Anne Marie Helmenstine at About.com's Chemistry page. Here's what we did:

Baking Soda and Sugar Carbon Snake

Sand

lighter fluid

baking soda

powdered sugar

1. Mix 4 tsp sugar and 1 tsp baking soda.
2. Make a mound with the sand. Push a depression into the middle of the sand.
3. Pour the alcohol or other fuel into the sand to wet it.
4. Pour the sugar and soda mixture into the depression.
5. Ignite the mound, using a lighter or match.

Anne Marie goes on to write:

At first, you'll get a flame and some small scattered blackened balls. Once the reaction gets going, the carbon dioxide will puff up the carbonate into the continuously extruded 'snake'. Actually, you don't even need the sand. I tried this project using baking soda and sugar in a metal mixing bowl, added the fuel, and lit the mixture. It worked fine. The old firework snakes had a distinct smell. These have a smell too... burnt marshmallows! If you use pure ethanol, sugar, and baking soda, then there is nothing toxic about this project. One caution: Don't add fuel to the burning snake, since you risk igniting the alcohol stream.

We got the puff balls, but the snakes were kind of stumpy. If you watch the video, you can see that the level of anxiety over this experiment overshadowed the excitement as well:

Here's how Anne Marie explains the reaction:

How Black Snakes Work
The sugar and baking soda snake proceeds according to the following chemical reactions, where sodium bicarbonate breaks down into sodium carbonate, water vapor, and carbon dioxide gas while burning the sugar in oxygen produces water vapor and carbon dioxide gas. The snake is carbonate with black carbon particles:

2 NaHCO₃ -> Na₂CO₃ + H₂O + CO₂
C₂H₅OH + 3 O₂ -> 2 CO₂ + 3 H₂O