Lesson 2 of 6
The word equation
Goal: Write the word equation for photosynthesis.
Photosynthesis is a chemical reaction. A word equation shows what goes in and what comes out.
carbon dioxide + waterlightchlorophyllglucose + oxygen
- Reactants go in. Carbon dioxide and water are used up.
- Products come out. Glucose and oxygen are made.
- Light and chlorophyll go above the arrow. The reaction needs both, but neither is a reactant. Light is the source of energy, and chlorophyll absorbs it.
- No chlorophyll, no photosynthesis. The white edges of the leaves in the picture have no chlorophyll, so they cannot make glucose.
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Key words in this lesson
Photosynthesis How plants and algae make glucose, using energy from light
Glucose The sugar made in photosynthesis: a plant’s food
Chlorophyll The green substance that absorbs light
Carbon dioxide The gas a plant takes in for photosynthesis
Oxygen The gas given out in photosynthesis
Reactant A substance that is used up in a chemical reaction
Product A substance that is made in a chemical reaction