Carbon snake is a demonstration of the

dehydration reaction In chemistry, a dehydration reaction is a chemical reaction that involves the loss of water from the reacting molecule or ion. Dehydration reactions are common processes, the reverse of a hydration reaction. Dehydration reactions in organic ch ...

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. The carbon snake experiment can sometimes be misidentified as the

black snake Black is a color which results from the absence or complete absorption of visible light. It is an achromatic color, without hue, like white and grey. It is often used symbolically or figuratively to represent darkness. Black and white ha ...

, "sugar snake", or "burning sugar" reaction, all of which involve

baking soda Sodium bicarbonate (IUPAC name: sodium hydrogencarbonate), commonly known as baking soda or bicarbonate of soda, is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation ( Na+) and a bicarbonate anion ( HCO3� ...

rather than sulfuric acid.

Explanation

Concentrated sulfuric acid can perform a dehydration reaction with

table sugar White sugar, also called table sugar, granulated sugar, or regular sugar, is a commonly used type of sugar, made either of beet sugar or cane sugar, which has undergone a refining process. Description The refining process completely removes ...

. After mixing, the color changes from white to brownish and eventually to black. The expansion of the mixture is the result of

vaporization Vaporization (or vaporisation) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenomenon ...

water Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...

and CO₂ inside the container. The gases inflate the mixture to form a snake-like shape, and give off a burned sugar smell. The

granularity Granularity (also called graininess), the condition of existing in granules or grains, refers to the extent to which a material or system is composed of distinguishable pieces. It can either refer to the extent to which a larger entity is sub ...

of the sugar can greatly affect the reaction: powdered sugar reacts very quickly but sugar cubes take longer to react. When sucrose is dehydrated, heat is given out to the surroundings in an

exothermic reaction In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change Δ''H''⚬ is negative." Exothermic reactions usually release heat. The term is often confused with exergonic reaction, which IUPAC defines ...

, while

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...

and liquid water are produced by the decomposition of the sugar: :C₁₂H₂₂O₁₁ + H₂SO₄ + 1/2 O₂ → 11 C + CO₂ + 12 H₂O + SO₂ As the acid dehydrates the sucrose, the water produced will dilute the sulfuric acid, giving out energy in the form of heat. :C₁₂H₂₂O₁₁ → 12 C + 11 H₂O

Alternative experiment

Paranitroaniline can be used instead of sugar, if the experiment is allowed to proceed under an obligatory fumehood. With this method the reaction phase prior to the black snake's appearance is longer, but once complete, the black snake itself rises from the container very rapidly. This reaction may cause an explosion if too much sulfuric acid is used.

References

External links

{{commonscat, Carbon snake
Dehydration of sucrose with sulfuric acid
ChemEd X
Sugar snake (Sugar and Baking soda)
MEL science
Sugar Snake: Sulfuric Acid and Sugar
youtube.com Chemistry classroom experiments Articles containing video clips

Explanation

Alternative experiment

See also

References

External links