Demonstration: Carbon Soufflé
Purpose
To show how large molecules, such as a carbohydrate like sugar, can be broken down into smaller
substances.
Carbon, oxygen, and hydrogen are combined in the presence of chlorophyll and sunlight in the plant to
produce carbohydrates.
In this demonstration, you will use sulfuric acid to dehydrate the sugar, leaving carbon.
C12H22O11(s) + 11 H2SO4(l)
12 C(s) + 11H2SO4 H2O
Teacher notes:
In this demonstration, many terms and ideas are presented. The first one is the definition of 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.
Another important idea is that of a dehydrating agent, such as sulfuric acid. The sulfuric acid acts really like
a catalyst to help break apart or decompose the compound, sucrose, into the elements that make it. After the
reaction proceeds, the plastic cup melts and this is evidence for the exothermic nature of the reaction.
Make sure this experiment is performed outside! This should last 20 minutes!
While outside, initiate peer discussion by asking them what did they see, etc.
Make sure you reintroduce physical and chemical changes.
Materials
Small beaker, 250-mL (Use an old one because it will be hard to clean)
Sucrose, C 12 H 22 O 11 (granulated table sugar) (fill the beaker to the 50mL line)
Sulfuric acid, H 2 SO 4 , concentrated (18M), 60 mL
Baking soda (for neutralization after reaction)
Gloves
Apron
Goggles
Safety
This demonstration will generate heat, which would possibly crack the beaker, and copious noxious fumes
consisting of water mixed with sulfuric acid. It must be done in a hood or outside.
Handle concentrated sulfuric acid with extreme care.
Use gloves, safety goggles, and a safety shield.
Procedure
Do this demonstration in a well-ventilated area or in a fume hood. Fill the beaker with granulated table sugar
to the 50mL line. Add 60 mL of concentrated sulfuric acid to the sugar in the beaker and swirl the beaker
gently. After a moment or two, the reaction will proceed very quickly. Watch for a reaction to occur as
evidenced by a color change where the acid contacts the sugar. The whole mixture will “puff up”
dramatically.
When the reaction is complete, you should neutralize the reaction with baking soda. After viewing the
products, they can be placed in a plastic bag and discarded once the entire reaction is cooled and neutralized.