The carbon snake is a demonstration of the dehydration reaction of sugar by concentrated sulfuric acid.
With concentrated sulfuric acid, granulated table sugar (sucrose) performs a degradation reaction which changes its form to a black solid-liquid mixture.
Concentrated sulfuric acid can perform a dehydration reaction with table sugar.
The gases inflate the mixture to form a snake-like shape, and give off a burned sugar smell.
[2] When sucrose is dehydrated, heat is given out to the surroundings in an exothermic reaction, while graphite and liquid water are produced by the decomposition of the sugar:[3] As the acid dehydrates the sucrose, the water produced will dilute the sulfuric acid, giving out energy in the form of heat.