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Title: Investigation 7: Modeling Photosynthesis
Name __________________________
Introduction
Everything in our world is made up of atoms. There are about 82 different types of atoms that occur
naturally on our planet. These atoms join with each other to make up groups called molecules. It’s
like different Lego pieces getting put together to make whatever you want to make. Some of the
atoms are better at joining together than others, just like some legos seem to fit together more
easily than others. It is the same with atoms. Some go together more easily
and some need lots of work and energy to get together. You use energy from
food to put the legos together. Plants use the energy from the sun to take
some molecules apart and then make other larger molecules.
Photosynthesis - Chlorophyll is the molecule that absorbs sunlight and uses
its energy to synthesize carbohydrates from CO2 and water. This process is
known as photosynthesis. Photosynthesis is the process by which plants use
the energy from sunlight to produce sugar, which cellular respiration converts
into ATP, the "fuel" used by all living things. The conversion of unusable
sunlight energy into usable chemical energy comes from the chlorophyll,
green pigment. This happens inside a leaf in structures called chloroplasts.
No light means no chlorophyll which means no photosynthesis.
Modeling Photosynthesis
When plants produce food using light energy, the chemicals involved undergo a chemical change or
a chemical reaction. The inputs are the reaction of light, water, and carbon dioxide. The atoms in
the water and carbon dioxide are rearranged using the energy from the light.
Group members – work:
Objective – Problem Statement:
Use the models of the inputs of water and carbon dioxide to produce the models of the outputs,
which are glucose and oxygen.
6CO2 + 6H2O  C6H12O6 + 6O2
Inputs
outputs
Materials:
Ball and stick kits
Procedure:
Use the ball and stick models to change the reactant (inputs) from this reaction to make the
products (sugar and oxygen). You should start with 6 molecules of carbon dioxide and 6 molecules
of water. The outputs or products of this reaction are glucose, a simple sugar, and oxygen. The
plant does not use the oxygen for photosynthesis. The oxygen is released into the atmosphere or
used by the plant to go through cellular respiration and to break the sugar down and release the
energy that is stored.
Data:
Draw a picture of the molecules in 3-D as have created them
Inputs (reactants)
6 Carbon Dioxide + 6 Water
Light Energy
Outputs (products)
Glucose
+
6 Oxygen

Construct a glucose molecule using the following guidelines:
1. Black = Carbon ; Red = Oxygen; Yellow = Hydrogen
2. 5 Carbon and 1 Oxygen makes a circle
3. 4 O-H come off of the circle
4. 1 carbon comes off of the circle
5. Every hole must be filled in with a bond
Analysis Questions
Were any of the atoms “left over” after you made the products?
Which product(s) is converted to starch by the plant?
What does the starch do for the plant?
Oxygen is also produced in this reaction. What does the oxygen do for the plant?
The products of this reaction are very important to humans. Do you agree or disagree with
this statement? Explain your answer using specific examples to support your position.
6. Did you use energy to rearrange the spheres in the models during the photosynthesis
reaction?
7. Do plants need energy to make this reaction happen? Where does this energy come from?
8. Which of the molecules that you made during the reaction stores the most energy?
1.
2.
3.
4.
5.
Conclusions:
1. Write a conclusion about the relationship between chlorophyll and photosynthesis. Describe
the relationship. What data supports your conclusion?
2. Write a conclusion about the relationship between light and photosynthesis. Describe the
relationship. What data supports your conclusion?
Investigation 7 A: Modeling Photosynthesis (Part I)
Data Sheet:
1. Using all of the pieces provided create CO2 and H2O. Draw the resulting molecules in the boxes provided. Remove any leftover pieces and place them back in the
box.
2. Now tear apart your CO2 and H2O and reform them into C6H12O6 and O2. Draw the resulting molecules in the spaces provided.
Drawing of CO2 Molecules
Drawing of H2O molecules

Drawing of Glucose molecules
Drawing of Oxygen molecules