Carbon snake
{{Short description|Experiment demonstrating the dehydration of sugar by sulfuric acid}}
{{distinguish|Black snake (firework)}}
[[File:Carbon snake2.jpg|thumb|A column of porous black
graphite formed during the experiment.]]
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.{{Cite book|title=Chemical Demonstrations a handbook for teachers of chemistry volume 1 |url=https://uwpress.wisc.edu/books/1740.htm |last=Shakhashiri|first=Bassam Z.|last2=Shreiner|first2=Rodney|last3=Bell|first3=Jerry A.|publisher=University of Wisconsin Press |year=2011|isbn=978-0-299-08890-3|pages=77–78|chapter=1.32 Dehydration of Sugar by Sulfuric Acid}} The carbon snake experiment can sometimes be misidentified as the black snake, "sugar snake", or "burning sugar" reaction, all of which involve baking soda rather than sulfuric acid.
Explanation
Concentrated sulfuric acid can perform a dehydration reaction with table sugar. After mixing, the color changes from white to brownish and eventually to black. The expansion of the mixture is the result of vaporization of water 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 of the sugar can greatly affect the reaction: powdered sugar reacts very quickly but sugar cubes take longer to react.{{Citation|title=Don't Try This at Home - 3 - Sulfuric Acid and Sugar|url=https://www.youtube.com/watch?v=zg9wmU7Z-6s|language=en|access-date=2022-01-31}}
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:{{Cite book|title=Spectacular Chemical Experiment |last=Roesky |first=Herbert W. |url=https://www.wiley.com/en-us/Spectacular+Chemical+Experiments-p-9783527815241 |publisher=Wiley|year=2007|isbn=978-3-527-31865-0|pages=17|chapter=Experiment 6: Sugar coal by splitting off water from sugar with sulfuric acid}}
:C12H22O11 {{sub|({{serif|s}})}} + H2SO4 {{sub|({{serif|aq}})}} + 1/2 O2 {{sub|({{serif|g}})}} → 11 C {{sub|({{serif|s}})}} + CO2 {{sub|({{serif|g}})}} + 12 H2O {{sub|({{serif|g}})}} + SO2 {{sub|({{serif|g}})}}
As the acid dehydrates the sucrose, the water produced will dilute the sulfuric acid, giving out energy in the form of heat.
:C12H22O11 {{sub|({{serif|s}})}} → 12 C {{sub|({{serif|s}})}} + 11 H2O {{sub|({{serif|l}})}}
Alternative experiment
Paranitroaniline can be used instead of sugar, if the experiment is allowed to proceed under an obligatory fumehood.{{Cite book|title=Chemical Demonstrations: A Sourcebook for Teachers Volume 1|last=Summerlin|first=Lee R.|last2=Ealy|first2=James L. |url=https://eric.ed.gov/?id=ED286722 |publisher=American Chemical Society |year=1988 |isbn=978-0-841-21481-1|edition=2nd|pages=171|chapter=Experiment 77: Dehydration of p-Nitroaniline: Sanke and Puff}} 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.{{Cite web|date=2013-06-06|title=Carbon Snake: demonstrating the dehydration power of concentrated sulfuric acid|url=https://communities.acs.org/t5/Educators-and-Students/Carbon-Snake-demonstrating-the-dehydration-power-of-concentrated/td-p/7732|access-date=2022-01-31|website=communities.acs.org|language=en}} This reaction may cause an explosion if too much sulfuric acid is used.{{Citation|title=Making a carbon snake with P-Nitroaniline|url=https://www.youtube.com/watch?v=YKHUnHDphTc|language=en|access-date=2022-01-31}}
See also
References
{{reflist}}
External links
{{commons category|Carbon snake}}
- [https://www.chemedx.org/video/dehydration-sucrose-sulfuric-acid Dehydration of sucrose with sulfuric acid] ChemEd X
- [https://melscience.com/en/experiments/sugar-snake/ Sugar snake (Sugar and Baking soda)] MEL science
- [https://www.youtube.com/watch?v=nqDHwd9rG0s Sugar Snake: Sulfuric Acid and Sugar] youtube.com