Simulated Stomach

OBJECTIVE

You can see the difference between regular, buffered, and enteric (coated) aspirin by testing the tablets in neutral, acidic, and basic solutions. Your stomach is acidic, but your small intestine is basic. These chemical opposites are separated by the pyloric valve, which opens only briefly to transfer partially digested food from the stomach to the intestine.

MATERIALS (per group)

• safety goggles
• 9 plastic cups
• 600 mL water
• 300 mL vinegar
• 45 g baking soda
• stop watch

PROCEDURE

1. Add 100 mL of water to each of three labeled plastic cups.
2. Record the time. Simultaneously add a regular aspirin tablet to one cup, a buffered aspirin tablet to the second, and an enteric aspirin tablet to the third.
3. Record any changes in the tablets at 30-s intervals until no further change is evident.
4. Repeat steps 1-3 using vinegar in each cup instead of water.
5. Repeat steps 1-3 again, using 15 g of baking soda in 300 mL of water in each cup.

Observations

On a sheet of paper, make separate tables and record your observations of water, vinegar, and baking soda solution reactions.

FOLLOW-UP

1. Why was water used for the experiment? 

2. What purpose did the vinegar serve? 

3. Why was the baking soda solution used?

Lesson 4

Acids and Bases Unit

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