Investigating Starch in Foods

Darlene Schleis, Glen Lake Elementary, Minnetonka, MN
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This lesson would be used during our nutrition unit when discussing carbohydrates. In this classroom activity students investigate which foods have starch in them by using iodine, as well as investigate the result of iodine and lemon juice on paper by doing some "Magic Writing." Students will do a "Magic Writing" activity where they write a message on a piece of paper and predict what will happen when the paper is submerged into a water/iodine solution. Based on what the students observed/learned in the "Magic Writing" activity, students will predict what will happen if iodine comes into contact with a starch found in certain foods. Students will then use an eyedropper to put iodine on several food samples and record their observations. They will list food from the different food groups that tested positive for starch.

Learning Goals

This activity is designed for students to hypothesize what will happen next.
This activity is designed for students to use higher order thinking skills and to think of a way to change the experiment to find out something new.

The students will discover that iodine is a good test for starch.
The students will discover that carbohydrates usually have starch present.
The students will use observation and recording of data to determine when starches are present.

Vocabulary: carbohydrate, starch, iodine, hypothesis

Context for Use

This lesson is intended for grade 3 students during their nutrition unit. They would have already learned about the food groups and had experience with recording observations and making hypothesis. There would also need to be a discussion about iodine; what it is used for and how it is poisonous. Students could work with a partner or in a small table group. You will need 2 class periods for this extension.

Description and Teaching Materials

Day 1
1. Discuss with a partner then whole group what students know about iodine and lemon juice. Record on board/activboard.
2. Go over directions to "Magic Writing" and demonstrate what the students will be doing (see attachment).
3. Students share their prediction with their neighbor and record their prediction.
4. Students do the "Magic Writing" experiment, have stations already set up.
5. Discuss results.
6. Have students come up with something from the experiment that they would like to find out and then change one part of the experiment to find out their answer.
7. Discuss what they learned.
Parts are adapted from Janice VanCleave's 200 Gooey, Slippery, Slimy, Weird and Fun Experiments and Louis V. Loeschnig's No Sweat Science: Chemistry Experiments.

Day 2
Students will use what they learned in Day 1 to test different foods for starch.
1. Discuss how they can determine if there is starch in different foods.
2. Discuss which foods they think have starch in them. Why?
3. Put small pieces of food on a paper towel and students will put a drop of iodine on it. (Have stations already set up. Include food from the bread, meat, vegetable and fruit, and dairy group.)
4. Students record their observations in a chart.
5. Discuss results. Ask students what other foods they could try and what results they think they would have.
6. If time, view on United Streaming- Food and Nutrition-Carbohydrates (1:19 duration). Also, Brain Pop- under Health-Nutrition.
Parts are Adapted from the book Jr. Boom Academy. Magic Writing (Microsoft Word 33kB Jan4 10)

Teaching Notes and Tips


Students will turn in their "Magic Writing" packet with their hypothesis and observations and their charts from "Starch in Food." There is also an assessment from the Great Body Shop that students will complete that includes test items on carbohydrates and starches. I will also have students complete a Tree Map on Carbohydrates to see if students are able to list foods that are carbohydrates and a Nutrition Taxonomy that includes vocabulary that was learned in the lesson.

Standards Record of Observation Construct Reasonable Explanations

References and Resources