Activity

Molecular modelling of yeast converting sugar to gas

Summary
Use molecule models to show how yeast breaks sugar molecules into carbon dioxide and ethanol. Use to model why bread rises.
Science content
Biology: Features, Adaptations of Living Things (K, 1, 3, 7)
Chemistry: States of Matter, Properties of Materials (K-7)
Chemistry: Atoms, Molecules (3-7)
Chemistry: Chemical Changes (2, 7)
Materials
  • Sets of molecular model pieces. One set has 6 carbons, 12 hydrogens, 6 oxygens, plus 24 bonds. Sets can be plastic modelling sets or home made sets with jelly beans/coloured marshmallows.
Procedure

Students model what happens to sugar molecules as yeast eats them.

Give each student/student group a sugar molecule (C6H12O6).
Tell them that one of the products as yeast breaks glucose apart is ethanol, and show them how to build it (CH3CH2OH).
Ask them to make two identical molecules with the atoms that remain. (Two CO2 molecules). It might be a challenge to figure out that there are two double bonds in CO2.

Once they have all made the CO2 molecules, spell out the name while pointing at the atoms "C-O-2", and some students may recognize the name and know it is carbon dioxide.
Ask what state of matter CO2 is (gas), and ask what might happen if this gas is stuck in bread dough (it will make it rise).

Attached documents
Grades taught
Gr 3
Gr 4
Gr 5
Gr 6
Gr 7
Teaching site
Gordon Elementary
ingridscience afterschool
Laurier Elementary
New York Hall of Science
Tyee Elementary