Chemicals That Come from Amazing and Wonderful Plants!
Standards Addressed
3.1.5 Demonstrate the ability to work cooperatively while respecting the ideas of others
and communicating one’s own conclusions about findings
3.1.2 Participate in different types of guided scientific investigations such as observing
objects and events and collecting specimens for analysis
3.1.4 Discuss the results of investigations and consider the explanations of others
Objectives
The student should be able to:
1. Write a sentence that reports their observations including characteristics such as color
and taste
2. Write a sentence that describes changes in characteristics
3. Identify changes in color as a chemical reaction
Required Materials
Radishes
Red cabbage
Grape juice (concentrate)
Vinegar
Baking soda
Plastic cups
Measuring spoon
Water
Pieces of ginger root
Fresh mint
Cinnamon stick
Lemon
Spearmint or peppermint gum or candy
Stalk of celery
Taller cups
Butter knife
Metric ruler
Food coloring (blue works best)
Carnations
Lesson Introduction
Paper bags or boxes
Zip lock bags
Chemicals from natural products make food taste and smell better and can serve many
other purposes. They can come from roots, fruit, stem, leaf or flower parts of plants.
Plants are composed of some parts we can’t see easily with our eyes such as tubules that
carry water through the plant. Plants contain chemicals that can react with other
substances to indicate acidity or alkalinity by changing colors and can be useful in many
other ways.
As the teacher walks around observing the groups, he or she should ask them if certain
smells or tastes remind them of anything they had smelled or tasted before. Why do they
like the item they selected as their favorite? Ask students about their observations. Ask
them to compare and contrast aspects of their observations (smells, tastes, visible
characteristics).
During the demonstration ask the students what they think will happen. After the
demonstration, ask them why they thought the changes took place. The changes take
place because there are chemicals in red radishes, red cabbage, and grape juice that may
indicate pH in alkaline or acidic environments. To third graders the teacher might just
point out that acids are sour like lemon juice. Introduce the idea that things smell or taste
differently because of the presence of different chemicals.
Procedure
1. Instruct the students to come over to the place where a demonstration will take place,
showing how natural chemicals from plants can change in the presence of other
natural chemicals.
2. Details for the demonstration: Grate the skin off 4 or 5 radishes. Place it into one of
the cups. Add warm water. Allow the water to turn a pink color. Divide the water
into 3 cups. One is a control. To one cup add a small amount of vinegar. To the
other cup add a small amount of baking soda. Divide grape juice into three cups.
Add a little vinegar to one and baking soda to the other. Red cabbage may also
change colors in the presence of vinegar or baking soda. Tear up 2-3 leaves of red
cabbage and place in a zip lock bag. Add warm water. Press the bag until the water
is deep blue. Repeat dividing the cabbage water into three cups and add vinegar to
one and baking soda to the other. Ask the students why the warm water became
colored (blue) and why do they think the color change with vinegar occurred.
3. After the demonstration, divide the students into groups of four. You may designate
their jobs any way you like. Possibly one student may obtain the materials, one
student may write down observations, one person may read the assigned questions to
the group, one person may ask questions of the teacher.
4. Give students instructions such as get one red bag with your group number from the
teacher or supply table. In the red bag are flavors that come from plants that we can
smell (ginger root, mint leaves, cinnamon stick, lemon). Ask the students to pass the
items around and answer the questions on the worksheet.
5. Instruct the students to obtain part of a stalk of celery. Cut a little off each end of the
stalk. Put it in a little bit of water. Add a few drops of food coloring (blue works
best). Leave the celery in the colored water for 3-4 hours.
6. Instruct the students to cut a little of the stem off a carnation. Add water and a few
drops of food coloring. It may take overnight to see the color move up the tubules to
the flower.
7. Instruct the students to write their observations and answer the questions on the report
sheet.
8. Ask the assigned group member to obtain a blue bag from the teacher or supply table.
In the blue bag are things we can taste (spearmint candy or gum, peppermint candy or
gum and wintergreen candy or gum). Ask the students if the smells or tastes remind
them of anything they have seen or smelled before (mint leaves). Ask the students to
discuss and write their observations.
Closure
After the students have finished their discussion you may tell them that ginger root is
used to make ginger ale, and that mint comes from the leaf part of the plant and is used to
make mint candy or gum. Cinnamon stick comes from the inner bark of a tree. Lemon is
a fruit from a plant. Carnations are a flowering part of the plant and can be used to make
perfume.
Assessment
Assessment for this lesson is teacher observation of how well students worked together
cooperatively, completion of the worksheet, the presence of discussion about their
observation of the items, and their explanation of the results of the demonstration.
Extensions
Provide library books about plant physiology, natural products from plants, grow an herb
garden in the classroom.
Connections
Students could write about their observations of the celery in the food coloring, or their
reasoning behind the color changes in the demonstrations. The celery could also be used
as a measuring exercise if the students were instructed to measure a certain length of
celery.
Created by Carolyn Weddle of the Ball State PIE program and Debbie Janowicz , a third
grade teacher, as a 3rd grade exercise. This is a modified WonderScience Activity.
Work Sheet
Name________________________
Group Number________
Please write your answer in complete sentences.
1. a. Of the plant parts you smelled, which was your favorite? Why?
2. From what part of a plant do you suppose it comes?
3. a. Which was your favorite taste from the blue bag? What color is it?
4. From what part of the plant do you think the flavor comes?
5. Did any of the things remind you of anything you’ve seen or tasted before?
6. Why do you think some of these items smell or taste the same…. Or differently?
7. What color did you add to your celery? What change do you think you will see?
8. What color did you add to your carnation? What change do you think you will
see?