Carbon Souffle (Decomposition of Sucrose)
Author: Dean Papadakis
Science Kit - Teacher's Guide
SED 695B
Overview : This demonstration is the
Decomposition of Sucrose. First we will look at the definition of the term
“CARBOHYDRATE”, by examining the formula for sucrose. Next we will perform the experiment and make observations. The balanced chemical equation for the reaction can be written and examined. The reaction can be repeated by replacing the granulated sugar with powdered sugar, so that you can investigate the affect of changing the particle size and therefore, concentration, on the rate of the reaction.
Set up of the materials for the Carbon Souffle
C
12
H
22
O
11(s)

12 C
(s)
+ 11 H
2
O
(g)
+ NRG
The general formula for the sucrose is C x
(H
2
O)y
H
2
SO
4 (aq)
is the dehydrating agent that catalyzes this decomposition reaction.
Since the energy term is a product, this is an
EXOthermic reaction.

EXPERIMENT SUMMARY
In this demonstration, many terms and ideas
are presented. The first one is the definition of
Topics:



Organic Chemistry & Biochemistry
Reaction Rates
Conservation of Matter & Stoichiometry
the term, carbohydrate
. This term is
describing the fact that sugar contains two
substances, which are the element carbon and
the compound water. Since people have an
idea what carbon looks like, as in the form of
charcoal, they will recognize one of the
products of this decomposition as the element
carbon. When the other product, water is
formed, it is formed as a gas due to the large
amount of heat that is produced, and the
water can be seen as STEAM.
Standards: frequency of collision of reactant molecules. As a basis for
Another important idea is that of a
The conservation of atoms in chemical reactions leads to the dehydrating agent
, such as sulfuric acid. principle of conservation of matter and the ability to calculate the mass of products and reactants. As a basis for understanding this
The sulfuric acid acts really like a catalyst to concept:
Students know how to describe chemical reactions by writing balanced equations.
help break apart or decompose the compound,
sucrose, into the elements that make it.
After the reaction proceeds, the plastic cup
Chemical reaction rates depend on factors that influence the
melts and this is evidence for the exothermic
nature of the reaction. understanding this concept:
Students know how reaction rates depend on such factors as After the experiment is performed, concentration, temperature, and pressure. Students know the role a it may be repeated by replacing the granulated catalyst plays in increasing the reaction rate. sugar with powdered sugar. This will
investigate how changing the surface area will
The bonding characteristics of carbon allow the formation of many
affect the rate of the reaction
. different organic molecules of varied sizes, shapes, and chemical properties and provide the biochemical basis of life. As a basis for understanding this concept:
The materials in this experiment can be
obtained from the store and will be much less
Students know the bonding characteristics of carbon that result in the formation of a large variety of structures ranging from simple
expensive than the $35 asked from Flinn
Scientific.
hydrocarbons to complex polymers and biological molecules.

Procedure :
Do this demonstration in a well-ventilated area or in a fume hood. Half-fill a plastic cup with granulated table sugar.
Place a glass stirring rod into the sugar. Add 5-10 mL of concentrated sulfuric acid to the sugar in the cup and begin stirring. After a moment or two, the reaction will proceed very quickly. When the reaction is complete, you should wash the cup and container in tap water, to remove any acid that remains. After viewing the products, they can be placed in a plastic bag and discarded. You may repeat the experiment using powdered sugar instead of granulated sugar, so that you can investigate how changing the surface area of a reactant affects the speed of the reaction.
Questions :
(1) What role does the sulfuric acid play?
(2) What is the general formula for a carbohydrate?
(3) What observations lead you to determine whether the reaction is endothermic or exothermic?
(4) What do you think was the composition of the gas that was produced?
(5) How would changing the particle size of the sugar from granulated to powdered, affect the rate of the reaction?
Applications to everyday life:
Since sucrose is a common substance (table sugar), examining its properties can be a useful thing. Additionally, the role
of the concentrated sulfuric acid, is as a “dehydrating agent”. One useful application of this is in the use of drain opener
which uses concentrated sulfuric acid as a means of decomposing paper items such as toilet paper that causes a drain pipe
to get clogged up. By understanding the role of the sulfuric acid in this demonstration, its role as a drain opener can be
better understood.



References & Links : http://www.flinnsci.com/