Kitchen Chemistry

I have used most of these experiments and demonstrations with elementary school kids--mostly K through 6th grades. A few have been used with college students. One or two have not been personally tested.

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Red Cabbage as a pH Indicator

References:
Of Cabbages and Chemistry GEMS Teacher's Guide (ISBN: 0-912511-63-X)
"Acid-Base Indicators Extracted from Plants", Chemical Demonstrations, Vol. 3, pp. 50-57.
"Cabbage Patch Detective", Fun With Chemistry, Vol. 1, pp. 53-63.

Equipment and Materials:

  • 1/2 small head of red cabbage
  • knife
  • distilled water
  • blender
  • measuring cups (or graduated cylinder)
  • measuring spoons (or graduated cylinder)
  • strainer
  • ziplock bags
  • hammer (or mortar and pestle)
  • clear plastic cups (or beakers)
  • variety of common materials such as:
    • vinegar*
    • clear ammonia*
    • baking soda*
    • lemon juice
    • tap water
    • clear soft drink (7-Up, Sprite)
    • milk
    • salt
    • sugar
    • milk of magnesia
    • antacid (Tums, Rolaids)
    • aspirin
    • acetaminophen (Tylenol)
    • sparkling mineral water
      *required materials

Procedure:
Chop the cabbage into 1-inch pieces.
Put 2 cups of chopped cabbage and 1 cup of distilled water in blender.
Blend for 1-3 minutes until cabbage is finely chopped.
Strain. Keep the liquid, discard the cabbage.

Add 5 mL (1 tsp) of indicator liquid to various substances in clear containers.
Note the color.
Substances must not be colored (e.g. cola) for true color to be seen. White substances (e.g. milk) are okay.
Tablets (aspirin, antacids) can be crushed by placing in a ziplock bag and carefully crushing with a hammer. Then dissolve in distilled water.

Additional Investigations:
Repeat using various fruit & vegetable dyes (blueberries, cherries, grape juice).

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Candy Chromatography

References:
"Candy Chromatography", Fun With Chemistry, Vol. 2, pp. 13-22.
"Analyzing Colors", ChemMatters, Dec. 1994, Classroom Guide.
"Chromatography of m&m Candies", M. Kandel, J. Chem. Ed., 69 (12), 988-989. (Dec. 1992 issue.)


Equipment and Materials:

  • samples of candy such as m&m's, Skittles, Reese's Pieces
  • set food colors for comparison
  • filter paper--or coffee filters cut into 8 cm x 8 cm squares
  • 0.1% salt solution (1/8 tsp salt in 3 cups water)
  • clear plastic 9 oz cups
  • blow dryer
  • toothpicks
  • small (1 oz) plastic cups

Procedure:
Put 4 candies (m&m's, Skittles, or Reese's Pieces) of the same color in a small cup.
Add 5 or 6 drops of water.
When the white color of the candy comes through, remove and discard the candy.
Add 4 more candies of the same color. Do not add more water!
Again, remove the candies when the white coating is visible.
Repeat with 3 more colors.
Spot on coffee filter paper; use a hair dryer to dry the paper.
Develop in 0.1 M salt solution.

Repeat using food colorings available in the grocery store.

We did not get quantitative, although this is certainly possible--especially with older students.

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Frozen Colloid (Ice Cream)

Reference:
"Making Ice Cream: Cool Chemistry", Robert Baxter, ChemMatters, Dec. 1995, pp. 4-7.


This recipe is modified from a Southern Living recipe (1978?).

Vanilla Ice Cream

  • 2 qts milk
  • 4 eggs
  • 1 1/2 cups sugar
  • 1 Tbsp corn starch
  • pinch salt
  • 1 can sweetened condensed milk ("Eagle Brand")
  • 1 cup whipping cream
  • 2 Tbsp vanilla extract

Put milk in a large pot and start heating over medium heat.
In a blender, blend eggs with sugar, corn starch, and salt.
Add about 1 cup of the warm milk to the egg mixture. Blend.
Add egg-milk mixture to rest of milk.
Cook over medium heat with constant stirring until mixture has thickened slightly.
Remove from heat and stir in sweetened condensed milk, whipping cream, and vanilla.
For best results, cool overnight in refrigerator.

Freeze in ice cream maker.

Makes 1 gallon.

To make this a science experiment, use thermometers to answer these questions:

  • What is the temperature of ice?
  • What did you find was the temperature of ice and salt?
  • What is the temperature of your freezer at home?

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Glowing Vegetables

References:
"The Incredible "Glowing" Pickle and Onion and Potato and...", P.M. Weimer and R. Battino, J. Chem. Ed., 73 (5), 456-457. (May 1996 issue.)
"Glowing Veggies", P. Scharlin, A.A. Cleveland, R. Battino, and M.E. Thomas, J. Chem. Ed., 73 (5), 457-459. (May 1996 issue.)

Web references:
A scholarly research paper
QuickTime movie of glowing pickle WARNING: 12 MB download!
In the spirit of T.W.I.N.K.I.E.S.

Disclaimer:
I haven't tried these myself. (I thought it would not be wise to give 1st graders the idea that they could plug pickles into their house current!) But with older students, this could be a real attention grabber. This is definitely in the same vein as these "classic" food entertainment experiments:

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Iron in Cereal

References:
"Iron for Breakfast", Fun With Chemistry, Vol. 1, pp. 49-52.
"Iron for Breakfast", Karen Schmidt, ChemMatters, October 1994, pp. 13-15.

Even though your body requires "ferrous" iron (Fe2+) for nutrition, most "enriched" breakfast cereals add metallic iron (also known as "elemental iron" or "reduced iron") as a nutritional supplement.

Equipment and Materials:

  • several different breakfast cereals
  • small aluminum loaf pans
  • pencils
  • magnets
  • Ziploc sandwich bags
  • cellophane tape
  • water
  • lots of white paper towels

Procedure:
For each cereal you wish to test:
Measure one cup of cereal into a Ziploc bag.
Crush the cereal, then pour it into a bowl.
Add one cup of water and stir to make a slurry. Add more water if necessary.
Tape a magnet to the eraser end of a pencil, and seal it inside a plastic bag.
Stir the cereal mixture with the magnet.
After ten minutes, examine the metal filings attracted to the magnet. (This is best done by wiping the magnet on a white paper towel.)
Stir for another five minutes and examine again.

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Popcorn

References:
"The Popcorn Pop", Fun With Chemistry, Vol. 1, pp. 71-75.
"Popcorn", Lynn K. Sibley, ChemMatters, October 1984, pp. 10-12.
"A Simple Laboratory Experiment Using Popcorn...", D. R. Kimbrough and r. R. Meglen, J. Chem. Ed., 71 (6), 519-520. (June 1994 issue.)
"Why Does Popcorn Pop?", F. C. Sauls, J. Chem. Ed., 68 (5), 415-416. (May 1991 issue.)

Popcorn explodes ("pops") when the moisture inside the kernel becomes steam and ruptures the outer covering.
Try popping popcorn that has been dried in an oven (250 degrees, several hours) or kept in a sealed container with additional moisture.
Compare to untreated popcorn.
It is also useful to compare brands and see if "gourmet" popcorn really lives up to its claims.

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Soap

Reference:
"Soap", Clair G. Wood, ChemMatters, February 1985, pp. 4-7.

I haven't made soap in years! When we did do it in class, we used the recipe on the can of lye and tried several different fats:

  • vegatable shortening
  • bacon grease
  • beef fat

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Vitamin C

References:
Vitamin C Testing GEMS Teacher's Guide (ISBN: 0-912511-70-2)
"Vitamin C in Peppers", ChemMatters, April 1995, Classroom Guide.
"Improved End Point Detection in the Redox Titratio of Vitamin C in Green Peppers", S.T. Deal and S. R. Pope, J. Chem. Ed., 73 (6), 547. (June 1996 issue.)
"Vitamin C Testing", WonderScience, Vol. 13, No. 6, Spring 1999, pp. 6-7.

You really need the GEMS book to perform this experiment.

Equipment and Materials:

  • small plastic cups to hold samples of material to be tested
  • small (1 oz) plastic cups for titrations
  • eyedroppers
  • stir sticks
  • indophenol solution (preparation is discussed in the GEMS guide)
  • Vitamin C tablets
  • distilled water
  • test materials such as:
    • orange juice
    • Hi-C
    • Tang
    • Kool-Aid

Procedure:
For each liquid you wish to test:
Put 2 tsp (10 mL) indophenol solution in a cup. (Indophenol is dark blue.)
Put 2 tsp water in a second cup.
Add one drop of the substance to be tested to each cup. Stir.
Continue adding drops to both cups (stirring after each drop) until the two cups are the same color. (Both should be nearly colorless.).

Indophenol color changes: Blue --> Violet --> Pink --> No Color

The WonderScience article has a procedure that uses easier-to-find materials.

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Wintergreen Lifesavers (Triboluminescence)

Reference:
"Light Your Candy", Linda M. Sweeting, ChemMatters, October 1990, pp. 10-12.

Equipment and Materials:

  • Wintergreen Lifesavers
    must be wintergreen and must have sugar
  • a very dark room
    an windowless bathroom is great--the mirror is handy if you do not have a partner
Procedure:
Carry the Lifesavers into the dark room and let your eyes adjust to the dark.
With your mouth open, crunch a Lifesaver with your teeth. Look for the green sparks!

The light is caused when the sugar crystal fractures. See the article for more information.

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Yeast & Sugar

References:
"Cookies and Yeast", Fun With Chemistry, Vol. 1, pp. 33-38.
"The Cookie Monster" and "The Sugar Test" in Kitchen Interactions, SAVI/SELPH
"Leavening: How Great Cooks Loaf", Melissa Rudolph, ChemMatters, April 1996, pp. 4-5.

Equipment and Materials:

  • yeast--lots of it (I bought it in 1 lb bags at a warehouse club)
  • large measuring cup: 2 cup or larger
  • measuring spoons
  • small Ziploc freezer bags
  • sugar
  • flour
  • water
  • rolling pin (to crush cereal)
  • thermometer
  • paper cups (for holding water)
  • paper towels (for clean up)
  • samples of finely crushed cereals and/or cookies

Procedure:
Label 5 Ziploc Freezer Bags with numbers 1 through 5.
Label additional Ziploc Freezer Bags with the names of the samples you wish to test.
Add 1 Tbsp of yeast to each bag.
Add the ingredients listed for each bag in the table below.
For each bag: Add 1/4 cup water. Squeeze out air and seal. Mix thoroughly.
After 20 minutes, measure the final volume of each bag with the large measuring cup, and record in the table below.

Record the temperature here:

Bag # Contents
(in addition to 1 Tbsp yeast + 1/4 cup water)
Final Volume
(oz)
1 nothing (control)  
2 1/4 tsp sugar  
3 1/2 tsp sugar  
4 1 tsp sugar  
5 1 Tbsp flour  
6 1 Tbsp crushed cereal. Name:  
7 1 Tbsp crushed cereal. Name:  
8 1 Tbsp crushed cereal. Name:  
9 1 Tbsp crushed cereal. Name:  
10 1 Tbsp crushed cereal. Name:  

Results:
Chart your results on a graph.
Can you tell how much sugar is in each cereal?

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DNA from Foods

References:
DNA Extraction with Kitchen Chemistry or a slightly more advanced version. University of Utah
"Liver and Onions: DNA Extraction from Animal and Plant Tissues", Nordell, et. al., J. Chem. Ed., 76 (3), 400A-B. (March 1999 issue)

I've had mixed results with this experiment, but when it works, it's a winner!

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Susan Wells Rollinson, rollinso@cfw.com
Remodeled July 2006. Updated 2/15/00.