What are the Reactants and Products in the Process of Photosynthesis?


Clare Marsigliano

Pearl River High School, Rockland


Columbia University’s Summer Research Program for Science Teachers

August 2012




Subject: Living Environment (Biology)

Grade Level: 9 & 10

Time Required:  3 x 45 minute periods



Prior knowledge: Students should be familiar with the fact that plants obtain food by use of sunlight, and, therefore, are called autotrophs.  Students also understand how atoms, when combined in specific proportions, will make up molecules.


Learning Targets:


·         Define photosynthesis

·         Describe the reactants and products of photosynthesis

·         Conduct an experiment to conclude the importance of sunlight in the health of a plant

·         Perform a play to show how reactants are used to produce products

·         Create a recipe for the process of photosynthesis



·         Projector or SMART board connected with iPad

·         Loose-leaf paper

·         Chart paper labeled with reactants and products names

·         Plant Experiment Lab Sheet (see materials in the lab sheet)



·         reactants, products, photosynthesis, autotroph


Period 1:


·         Students are asked to recall from where plants obtain food. 

·         Students should be able to respond with the fact that plants are able to obtain food from the use of sunlight.

·         Catalyst will be reviewed as a class.


Conduct Lab Experiment

·         Students will be asked to draw a hypothesis regarding plant growth.  The necessity and definition of a control will be reviewed.  Students will design a controlled experiment to test their hypothesis.

·         Students will collect the needed materials, and perform the experiment (data collection may take up to a week; students with the same hypothesis and procedure will compile their data to produce a greater sample size).  Students will conclude, after a week-long observation and data collection, that sunlight is very important in plant growth.

·         Ultimately, students should realize that the plant grows best in the sunlight when given water daily.


Period 2:

Catalyst:  Students will respond to the question- what is a reactant and what is a product?  The answer to this will be reviewed as a class.


Demo: The teacher will have a plant in the front of the room.  The teacher will give it water, breath on it, and place it on the windowsill.  The students will be asked to write down everything the teacher did in preparing the plant.



·         Teacher will discuss the required materials to allow photosynthesis to occur with use of the students’ observations of the demonstration.

·         Teacher will show video on YouTube “Photosynthesis by They Might be Giants

·         With the help of the students, the equation for photosynthesis will be displayed on the board


Kinesthetic Activity

·         Students will each be assigned an atom, which will be displayed on the small chart paper given to them (5x7 index cards work well too).  Students will either represent oxygen, hydrogen, or carbon.  In addition, a student will be assigned sunlight energy.  The students will be asked to group amongst themselves where they each belong in order to make up all of the reactants.  A photograph will be taken of the students in this organized formation of reactants. 

·         Students will then be subjected to the light of the sun.  With sunlight energy, the students will need to reorganize themselves into the groups that represent the products of photosynthesis.  A photograph will be taken of this final formation of molecules.



·         The photos of the classmates will be displayed on the projector.  First the reactants, and then the products.  The students will be asked to see if they notice any similarities in the reactants and products.  The students should be able to conclude that there is the same amount of students, holding the same atoms, but they are arranged in different molecules (groups) in the reactants picture compared to the products picture.  The teacher will suggest this is a chemistry concept of conservation.   The teacher will then ask the students what they believe is the most important product for the plant.  They should respond with glucose.  The teacher will also ask what is a very important product for us as humans.  They should respond with oxygen.

·         The teacher will finally stress the fact that plants are autotrophs because they are able to make their own food in the form of glucose.


Period 3:

Catalyst:  Students will be asked to write the full equation of photosynthesis in their notebooks.


Discussion: The teacher will compare photosynthesis to baking sugar cookies.  There are the ingredients in the cookies: sugar, flour, water, and so forth.  The way the reaction occurs is by the heat of the oven.  The final outcome is sugar cookies.  The reaction is similar to photosynthesis, with the necessary ingredients, the use of sunlight to allow the reaction to occur, and the final product including food for the plant.


Activity:  Students will be asked to write the process of photosynthesis as if it would be found in a recipe book.


Discussion:  The teacher will display the varying written recipes on the projector by use of the iPad camera.


Reflection:  Students will be asked what would happen if one of the ingredients were missing.  Students should be able to respond with the fact that the products will be very different if one of the ingredients in the cookies were missing, or if there was not enough of that ingredient added in the batter.  The key concept students should walk away with is that all of the reactants (in there respective quantities) are necessary for the reaction of photosynthesis to properly occur in the presence of sunlight. 



New York State Standards:


1.3a  Scientific explanations are accepted when they are consistent with experimental and observational evidence and when they lead to accurate predictions.

2.3c  Development of a research plan for testing a hypothesis requires planning to avoid bias (e.g., repeated trials, large sample size, and objective data-collection techniques).

6.1a  Energy flows through ecosystems in one direction, typically from the Sun, through photosynthetic organisms including green plants and algae, to herbivores to carnivores and decomposers.