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This lesson is designed as an introduction for writing and balancing chemical equations. Students will learn how the chemical reaction for photosynthesis affects their lives and their environment. The lesson demonstrates how our environment readily recycles chemicals.
ITV Series
Science Is Elementary: Let's Explore Plants (#1)

Learning Objectives
Students will be able to:

Pre-Viewing Activities
The information that follows can be listed on the chalkboard, or presented via a transparency. In either case, a separate hand-out sheet should be prepared and given to the students at the completion of the activity.

Explain that a chemical equation is:

A statement of facts about a chemical reaction that consists of reactants and products. Chemical equations are divided into four major classes.

The first being synthesis, where two simple reactants produce a complex product.

The second class is analysis. In this class, a complex reactant is broken down.

Single replacement is the third class, where one element replaces another element which makes up a compound.

The fourth class is called double replacement. In this class, elements are switched between two compounds.

Explain the synthesis reaction between Hydrogen and Oxygen: Hydrogen combines with oxygen to produce water. Write out the equation:

H2 + O2 = H2O

Explain to the class why Hydrogen is written as H2: Hydrogen and Oxygen are diatomic molecules, that is molecules with two of the same elements.

Now balance:

2H2 + O2 = 2H2O

Ask the students the following questions:

Can you list on the chalkboard some elements that are necessary for life? (Hydrogen, Oxygen, Nitrogen, and Carbon.)

The air we breath is made up of what element? (Oxygen)

List some other places this element can be found? (Water and plants.)

How do plants produce Oxygen? (Photosynthesis -- write this answer on the chalkboard.)

Ask the class: Would anyone care to explain exactly what photosynthesis is? (The chemical reaction where carbon dioxide reacts with water to produce glucose and Oxygen.)

Ask the students: Why is it that when some plant owners talk to their plants, the plants actually seem to grow better? (Humans exhale carbon dioxide when they speak, providing carbon dioxide for photosynthesis.)

As a conclusion to the pre-viewing activities, describe photosynthesis as:

Carbon dioxide is absorbed by the plants and reacts with water (either rain water or water from daily watering) to produce glucose and Oxygen. The Oxygen is given off into the environment which humans then inhale. The cycle begins again (or repeats itself).

Focus Viewing
To give the students a specific responsibility while viewing, tell them: As we view the following video segment, picture in your mind how this process could be diagrammed or drawn on the chalkboard.

Viewing Activities
video from the beginning of the program Science Is Elementary: Let's Explore Plants.

video when the apple appears on Miss Amato's desk. (3 minutes)

Post-Viewing Activities
Project on an overhead transparency the following diagram and explanation of photosynthesis.


The chemical equation for photosynthesis is
carbon dioxide plus water yields glucose and Oxygen.

On the chalkboard, write the following formula for each reactant and product. Ask the students to copy it on a separate sheet of paper.

CO2 + H2O = C6H12O6 + 6O2
First, explain the significance of each symbol (glucose should be given).

Next, explain chemical balancing: One Carbon atom on the left to six Carbon atoms on the right; therefore, six Carbon atoms are needed on the left.

Say to the class: Now, let's examine the number of Hydrogen atoms. Two Hydrogen atoms on one side of the equation to twelve Hydrogen atoms on the other. Therefore, six of the pairs are needed.

Say to the class: And now we are left with eighteen oxygen atoms on both sides.

6CO2 + 6H2O = C6H12O6 + 6O2

Action Plan
Balancing Equations
The information that follows can be listed on the chalkboard or presented via a transparency. In either case, a separate hand-out sheet should be prepared and given to the students.

Directions: Balance the following equations and write the names of each reactant and product.

H2 + O2 = H2O

Na + Cl2 = NaCl

Na + HOH = NaOH + H2

Mg + HOH = Mg(OH)2 + H2

NaOH + H2S = Na2S + HOH

Ca + NaCl = CaCl2 + Na.
Language Arts:
Write a short paper on how our environment recycles matter.

Home Economics:
Bake a cake and explain why the ingredients must be combined and balanced correctly. Describe what would happen if you had too much or not enough floor or other ingredients.

Solve word problems, like: Determine the mass of the reactants Hydrogen and Oxygen which are needed to produce five molecules of water.

Social Studies/Geography
Study the various types of plants that can be found in the world and how they react within their environment.

Draw a picture of a person talking to a flower or plant. Include the chemical equation and a diagram of the process that is taking place.

Master Teacher: Rowland V. Bynum

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