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Starch Test in Foods

Susan Wimberly                 Frazier Elementary School
940 Pleasant St.               4027 W. Grenshaw St.
Oak Park IL 60302              Chicago IL 60624
                               (312)534-6880

Objective:

This lesson was designed for use in fourth grade and satisfies Illinois State 
Goals 1, 3, and 4.

The student will be able to...
     - confirm a prediction by doing an appropriate experiment;
     - identify various foods which are starches.

Materials Needed:

newspaper                        small samples of food:
6 glass jars                           butter
tap water                              rice
20 plastic plates                      cheese
20 eyedroppers                         meat
20 starch charts                       potato (raw)
1-1 oz. bottle iodine tincture         apple
(NOTE: Iodine tincture is              salt
poisonous and eats through             flour
styrofoam!)

Strategy:

1.   Ask students how they enjoyed lunch (or breakfast) and what they ate for 
     that meal.  
2.   On the chalkboard, make a list of some of the foods students ate.  
3.   Write the word "starch" on the board and ask students if they know what 
     that means. 
4.   Explain that starch is a common form of complex carbohydrate that we 
     need to be healthy. 
5.   Explain that starch is stored in plants.  
6.   If not already on the board, write the foods from the "small sample of 
     food" list above.
7.   Ask students to predict, or guess, what foods on the board are starches, 
     and draw a star next to those foods.  
8.   Explain that you will test one of those foods to find out. 
9.   Cover work space with newspaper (iodine discolors surfaces).  
10.  Stir equal amounts of iodine and water into one jar.  
11.  Pour equal amounts of the solution into the other five jars and set aside 
     for later.  
12.  Place a piece of potato on the newspaper.  
13.  With an eyedropper, apply a few drops of the iodine solution to the potato.
     When exposed to starch, iodine turns dark brown or blue-black.  
14.  Ask students what the color change means.  
15.  Explain that the potato is a starch.   

Performance Assessment:

1.   Each student will receive a starch chart, eyedropper, and plastic plate 
     with a piece of each of the food samples listed above.  
2.   Each table of 4 students will receive a jar of the iodine solution to 
     share.  
3.   Explain that the students will first record their predictions in the first 
     column of the starch chart, and then they will apply a few drops on each 
     food sample.  Any change will occur within a few seconds. 
4.   Explain that after five minutes, students will record their findings in the
     second column of the starch chart.  
5.   Student predictions (column 1) may vary.  In column 2, the following 
     should be listed as starches: rice; potato; flour.  
6.   What do these samples have in common?  They all come from plants.  


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