Tuesday, September 4, 2012

Introduction to Chlorophyll

We're kick starting the school year with plant science.  The Core Knowledge sequence for Kindergarten (free download here) lists the following objectives:

• What plants need to grow: sufficient warmth, light, and water
• Basic parts of plants: seed, root, stem, branch, leaf
• Plants make their own food.
• Flowers and seeds: seeds as food for plants and animals (for example, rice, nuts,
wheat, corn)
• Two kinds of plants: deciduous and evergreen
• Farming
How some food comes from farms as crops
How farmers must take special care to protect their crops from weeds and pests
How crops are harvested, kept fresh, packaged, and transported for people to buy
and consume
This lesson on chlorophyll covers three of the above objectives - What plants need to grow (light), basic parts of plants (leaf), and plants make their own food.  It's an extremely simplified overview of what chlorophyll is, but I feel that it lays the foundation for future learning later on.

Lesson:  Introduction to Chlorophyll

Objective:  Student will conduct an experiment to illustrate how plants use chlorophyll.

Materials:  Black construction paper.  Green construction paper.  Scissors.  Sponge (the kind that has yellow on one side, and green scrubby on the other).  Glue.  Water.


1.  Cut out an oval leaf shape out of green construction paper.  Glue to black construction paper.  Cut sponge into little squares.

2.  Explain to student that the green paper represents a leaf.  Ask, "Why do you think leaves are green?" Encourage student to make several guesses.  You can reinforce the scientific process here, by saying, "That is a good hypothesis.  A hypothesis is like a guess.  Can you come up with another hypothesis for why leaves are green?  Here is my hypothesis _________ (don't say that it's because of chlorophyll - make up another hypothesis, to model that it's ok to not know the answer at the beginning of an experiment!)

3.  Say, "Did you know that leaves are made up of little things called cells?  The cells all have something called chlorophyll in them."  Indicate the pieces of sponge.  Say, "Let's pretend that these pieces of sponge are the leaf's cells.  The green part can be the chlorophyll.  Let's glue the cells onto the leaf."  Glue the sponges onto the leaf shape.

4.  Say, "Did you know that chlorophyll has a special job?  Let's pretend that this water is sunlight, and let's see what the chlorophyll does with the sunlight."  Pour a little water on a sponge.  Observe with the student what happens.  Say, "What happened to the chlorophyll?  What did it do to the sunlight?"  Discuss.  Say, "Chlorophyll's job is to soak up the sunlight.  The plant uses the sunlight for energy.  Let's give more 'sunlight' to the rest of the chlorophyll."  Continue pouring water on the sponges.

5.  Reiterate at the end that the chlorophyll's job is to collect sunlight for the plant to use for energy.