Problem:   How does your mouth start the process of digestion?

Materials:   6 test tubes, test tube rack, graduated cylinder, beaker, water, oatmeal, glucose, saliva, iodine solution, Benedict's solution, hot plate, safety goggles, apron, test tube clamp

Procedures:   test if saliva breaks down starch
 
 

test tube	1	2	3	4	5	6
iodine test
Benedict's test
starch present?
sugar present?

1. Put on your safety goggles.
2. Label six test tubes 1, 2, 3, 4, 5, and 6.  DONE!
3. Fill a beaker with 100 mL of water.  Soak a handful of oatmeal in the water.  Allow to stand for 10 minutes, stirring once or twice.  Pour off the milky-white liquid.  Use this as your starch solution.  DONE!
4. Put 1 cm of starch solution into test tubes 1, 2, and 3.
5. Put 1 cm of glucose (sugar) solution into test tubes 4, 5, and 6.
6. Wash the starch solution out of the beaker, fill it half full with hot tap water, and place it on a hot plate.  DONE!
7. Add 4 drops of iodine solution to test tubes 1 and 4.  Iodine will turn blue-black in the presence of starch.  Observe the test tube and record your observations by indicating a positive (starch present) or negative (no starch present) result.
8. Add 4 drops of Benedict's solution to test tubes 2 and 5 and heat them in the hot water in the beaker.  Benedict's solution is an indicator.  If sugar is present, it turns from muddy green to yellow to rust to red.  Record your observations.
9. Have one group member put clean saliva into test tubes 3 and 6.  THIS PERSON SHOULD BE THE ONLY PERSON HANDLING THESE TEST TUBES FOR THE REST OF THE LAB.
10. Swirl test tubes 3 and 6 carefully.  Wait five minutes.
11. Add 4 drops of Benedict's solution to test tubes 3 and 6.  Wait for the water bath to boil.  Using a test tube clamp, place test tubes 3 and 6 in the water bath and leave them there for five minutes.  Record your observations.
12. When finished with the lab, the person who contributed the saliva should clean out test tubes 3 and 6, and finish by putting the tubes in the antiseptic bath provided by your teacher.

Analysis/Conclusions

13. How did you test for the presence of starch?
14.  How did you test for sugar?
15. What can you conclude from your data?  What process begins as you chew your food?
16. Starches must be made up of more than one molecule of what chemical?