Mom might have told you "No spitting" when you were little, but now that you're older, it's "Spit, don't quit" -- at least, it is if you want to try this cool project. In the process, you'll learn something about enzymes.
Make sure you wear goggles when using iodine. Iodine will stain skin, as well as clothes, tables, and countertops, so be careful! Also, remember that spit may contain germs, so don't touch someone else's spit. Wash your hands after collecting spit and after cleaning up.
What You'll Need:
- Iodine (available from drugstores)
- 2 test tubes (or similarly shaped glasses)
- Measuring spoon
- 2 science stirrers (or coffee stirrers)
Step 1: Put on the goggles. Place a pinch of cornstarch on the plate. Add a drop of iodine. Notice the blue-black color that is produced. Iodine turns this color when starch is present.
Step 2: Put 2 milliliters water into test tube A.
Step 3: Gather your spit. Put 2 milliliters spit into test tube B. (Spit-gathering is easier if you think about lemons.)
Step 4: Mix 1/10 teaspoon cornstarch into each solution. Stir each solution. (Be sure to use a different stirrer for each test tube.)
Step 5: Place the test tubes in a warm place. Stir each test tube every 5 minutes. After 20 minutes, go on to Step 6.
Step 6: Add two drops of iodine to each test tube. Compare the test tubes.
Record your observations.
Test tube A turns a blue-black color, while test tube B has less of a color change. This shows that test tube A has more starch than test tube B. Spit, also known as saliva, contains the enzyme salivary amylase, which digests starch into sugars. This tells you that there is less starch in test tube B.
Don't get too used to spitting -- you'll need your sense of taste for the next experiment. Keep reading science projects for kids: nutrition and health to learn about your taste threshold.