DIGESTION

HYPOTHESIS

pH is a chemical property of liquids that tells whether the liquid is an acid or a base. Acids have free hydrogen ions and a pH of 1-6. Bases have free hydroxyl ions and a pH of 8-14. Distilled water in neutral with a pH of 7. What do you think might happen to the pH if an acid and a base are mixed together?

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MATERIALS NEEDED

3 bottle caps
1 8x11" sheet of paper
1 jar with lid
3 labels
5 1"-2" pieces of pH test paper
pH paper key
1 antacid tablet
distilled water
vinegar
glass cleaner
safety goggles

PROCEDURE

1. Label three bottle caps: distilled water, vinegar, glass cleaner.

2. Put a small amount of the appropriate liquid in each cap.

3. Test the pH of each and record it in the following table.

4. Which one is the acid? ____________________ the base? ____________________

5. Test your hypothesis by pouring one into the other. Shake the cap gently to mix the two.

6. Test the mixture with a clean piece of pH test paper and record the results in the table.

LIQUID	pH
Distilled Water
Vinegar
Glass Cleaner

7. Now let's model your stomach. Fill the jar about half way with vinegar. The jar will simulate your stomach and the vinegar will simulate the hydrochloric acid in your stomach.

8. Sometimes people get stomach aches and take an antacid to help. Let's see why. Wrap an antacid tablet in a piece of paper and carefully stomp on it until it is crushed.

9. Pour the antacid into the jar, put the lid on, and shake.

10. Test the pH: ________ What happened to the pH in the "stomach"?

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CONCLUSION

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QUESTION

What part of the digestive process did you simulate by stomping on the antacid?

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