The Decomposition of Sugar
Clues to a Chemical Change
By
Joseph A. Castellano, Ph.D.
RESEED Silicon Valley
What is Sugar?
 Sugar is a carbohydrate called sucrose
 Carbohydrates contain only carbon, hydrogen and oxygen
 The formula for sucrose is C12H22O11, but the structure
looks like two glucose molecules connected together
Can Sugar be Decomposed?
 Decomposition is a process that breaks down
molecules into new substances or even
individual atoms.
 In the following demonstration, sugar will be
decomposed into hydrogen and oxygen atoms in
the form of water, leaving behind only carbon.
 This OUTDOOR demonstration shows five
clues to a chemical change.
The Reactants
The Reaction
Demonstration must be done outdoors on a clear day
The Products
Water
Vapor
Clues to a Chemical Change
1. Color change
2. Gas formation
3. Temperature increase (>150oC)
4. Creation of an odor
5. Formation of a new substance
How the Chemical Change Works
 The sulfuric acid acts as a catalyst to remove
the hydrogen and oxygen atoms from the sucrose molecule
in the form of water vapor (steam).
 As the sugar decomposes, only carbon is left behind.
 The release of water causes the mass to swell so the carbon
takes up more space than the original sugar, producing a
from that looks like a mushroom.
 The heat generated by the reaction causes a small amount
of the sulfuric acid to decompose into sulfur trioxide
and sulfur dioxide, which are responsible for the foul odor
Decomposition of Sucrose is a
Dehydration Process
(Catalyst)
Eleven Water Molecules are Removed
1
7
9
2
6
8
3
10
4
5
11 H2O
11
Carbon Atoms Rearrange
1
8
2
9
3
6
4
5
7
12 C
10
12
11
Hexagon Shapes are Formed
Carbon Grows into a
Honeycomb Structure like Graphite
Graphite Structure
Summary
 Decomposition is a process that breaks down
molecules into new substances or even
individual atoms.
 Sugar is decomposed by sulfuric acid catalyst
into hydrogen and oxygen atoms in
the form of water, leaving only carbon behind.
 This demonstration shows five clues to a
chemical change.
This presentation was produced as a public service
to help middle school and high school science
teachers develop experiments and demonstrations
for use in their classrooms.
More science experiments and demonstrations are
available on the RESEED Silicon Valley web site:
www.reseed-sv.org.
RESEED (Retirees Enhancing Science Education through
Experiments and Demonstrations) is a program aimed at
stimulating greater interest in science by middle school
students.
Music: “Midnight Blue,” Kenny Burrell, Blue Note, 1999