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Facilitator/Educator Guide: Ow, My Tummy Hurts! The Biology and Chemistry of Gas Relief

Have you ever felt bloated? It could be because too much gas was trapped in your digestive system. How do some drugs relieve trapped gas? Find out using soapy water, jars or drinking glasses, straws, and some crushed tablets of simethicone, one drug that speeds the body's release of trapped gas.

Activity's uses: Demonstration or small group exploration
Area(s) of science: Life Science, Physical Science, Life Science
Difficulty level:
Prep time: < 10 minutes
Activity time: < 10 minutes
Key terms: Medical drugs, digestion, gastrointestinal syste, gastrointestinal gas, microorganisms, surface tension
Downloads and Links: Facilitator / Educator Guide PDF.
Student Guide web page or PDF.

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Background Information

Countless helpful microorganisms (mainly bacteria and yeast) live inside the gastrointestinal tract, or digestive system, to help your body digest food. As a byproduct of digestion, the microorganisms make gas. When these gas bubbles form, they can get trapped within the food being digested.

Although a little trapped gas in the gastrointestinal tract is normal, large amounts can cause problems. Some foods that contain a lot of starch, like beans, broccoli, and breads, can be difficult to digest and cause the gastrointestinal tract to make more gas. Other situations can cause extra gas, such as being under stress, swallowing lots of air, or having colon cancer. For a person to feel healthy, the gas from digestion needs to escape the body. People do this by belching, having flatulence, or taking some over-the-counter medicines, like simethicone.

Simethicone helps digestive gas leave the body at a faster rate by decreasing the surface tension of the trapped gas bubbles. To form, bubbles need the right amount of surface tension, which is a liquid's tendency to contract at its surface (due to cohesive forces pulling the liquid's molecules inward, toward the bulk of the liquid). For example, you have probably seen that making bubbles with plain water is difficult, but bubbles form easily with soapy water. This is because the surface tension of plain water is too great for bubbles to form, but soap decreases the water's surface tension enough so bubbles can form easily. (Soap molecules have a hydrophilic end that seeks to interact with water, and a hydrophobic end that does not; the soap molecules separate the water molecules this way. As the soap molecules space the water molecules farther apart, the cohesive forces between them decrease. This in turn decreases the surface tension.) Simethicone also decreases surface tension, but by a lot more than soap. In fact, simethicone decreases it so much that gas bubbles are not stable and they pop, letting trapped digestive gas escape and more easily pass through the body.

In this science activity, students will use detergent, water, jars or drinking glasses, straws, and some crushed simethicone tablets to investigate how simethicone can eliminate trapped gas.

For Discussion

This science activity can serve as a starting point for a variety of science and health discussions. Here are a few examples of questions that can be used to start a discussion:

  • How do you think simethicone will affect the formation of bubbles in soapy water?
  • How is gas created in the gastrointestinal tract?
  • How does surface tension enable bubbles to be made?
  • How are bubbles made using soapy water similar to trapped gas in the gastrointestinal tract? How are they different?
  • What does simethicone do in the gastrointestinal tract to get rid of extra gas bubbles?

Materials

Needed for preparing ahead:

  • Anti-gas chewable tablets containing simethicone (2 tablets per demo or small group). These may be purchased at a pharmacy, in the section related to digestion and gastrointestinal gas relief. Make sure the packaging indicates that the tablets contain simethicone.
  • Cutting board
  • Knife
  • Optional: Piece of wax paper
  • Spoon
  • Jars, drinking glasses, clear plastic cups, or vases (2 per demo or small group). They should be transparent and the same shape and size.

Needed for each demo or small group at the time of the science activity:

  • Jars, drinking glasses, or vases (2), with one receptacle containing the two crushed simethicone tablets and the other receptacle being empty
  • Water (enough to fill both jars)
  • Optional: Sticky notes and pencil or pen
  • Liquid dishwashing detergent (10 drops per demo or small group)
  • Straws (2 per demo or small group)
  • Timer or clock that shows seconds
Classroom Activity Gas Simethicone picture of materials
Figure 1. You need only a few simple household materials to do this fun science activity.

What to Do

Prepare Ahead (< 10 minutes)

  1. On a cutting board, use a knife to cut two simethicone tablets into small pieces. (You can do this on top of a piece of wax paper so it is easier to move the crushed tablets.) Use two tablets for each classroom demo or small group, but keep them separate.
Classroom Activity Gas Simethicone picture of simethicone tablets
Figure 2. For each group or small demo, place two simethicone tablets on a cutting board and cut them into pieces.
  1. Then use the back of a spoon to crush the small pieces into a fine powder.
Classroom Activity Gas Simethicone picture of crushed simethicone tablets
Figure 3. Crush the simethicone tablet pieces into a powder.
  1. Transfer the powdered simethicone to a jar, drinking glass, or vase. Each demo or group should have a jar with two powdered simethicone tablets and one that is empty.
Classroom Activity Gas Simethicone picture of crushed simethicone tablets in a jar
Figure 4. To do each classroom demo or small group, have one jar with powdered simethicone tablets and one empty jar ready.

Science Activity (< 10 minutes)

  1. Each classroom demo or small group should have one jar with two powdered simethicone tablets, one empty jar, water to fully fill both jars, liquid dishwashing detergent, two straws, and a timer or clock that shows seconds.
  2. Have students take both the empty jar and the one with simethicone and fill them about halfway with water. Students should keep track of which one contains simethicone and which does not. The water in the jar with simethicone should be cloudy and colored if colored tablets were used, but you can also use sticky notes as labels.
Classroom Activity Gas Simethicone picture of crushed simethicone tablets in a jar with water
Figure 5. Have students fill each jar halfway with water.
  1. Next have students add five drops of liquid dishwashing detergent to each jar. You add the detergent now so that when you pour in more water, it will help mix the detergent in.
  2. Now have students fill both jars with water to about an inch from the top of the jar. It is important to leave some space at the top of the jars for bubbles to form.
Classroom Activity Gas Simethicone picture of crushed simethicone tablets in a full jar with water
Figure 6. After adding the dishwashing detergent, have students fill each jar with water to about an inch from the top.
  1. Direct students to put a clean straw into each jar and mix each jar with its straw. Tell them to mix the detergent and simethicone powder well. You can ask students to make some observations at this point.
Classroom Activity Gas Simethicone picture of jars of water with straws
Figure 7. Have students put a straw in each jar and then mix the liquids well.
  1. Have students blow through the straws, one at a time, for ten seconds and observe what happens in each jar. Instruct students to slowly blow through the straw with equal force for both jars.
Classroom Activity Gas Simethicone picture of jar with bubbles and jar without bubbles
Figure 8. Instruct students to blow in each straw for ten seconds and observe the results.

Expected Results

When each jar was stirred with the straws, bubbles may have been apparent at the top of the water in the jar without simethicone, but no bubbles should have been visible in the jar with simethicone. After blowing through the straws, students should have seen many large bubbles accumulate on the top of the water in the jar without simethicone, but in the jar with simethicone no bubbles should have been visible on the top of the water. The detergent decreases the surface tension of the water so that bubbles can form, but the simethicone decreases the surface tension even more, so that the bubbles are not stable on the surface of the water and they immediately pop.

For Further Exploration

This science activity can be expanded or modified in a number of ways. Here are a few options:

  • Straws are used to create bubbles in soapy water in this activity, but students could make bubbles in other ways, such as by dropping an Alka-Seltzer® tablet or fizzy candy, like Pop Rocks®, in soapy water. Do bubbles made using these different methods look the same? Does simethicone appear to have the same effect on these bubbles?
  • In this activity, two powdered simethicone tablets were used with a certain amount of water. Students could try this activity again, but this time use different, smaller amounts of simethicone, such as one tablet, ¼ tablet, 1/32 tablet, etc., in the same amount of water. How little simethicone is needed to see the effect still that was originally seen?
  • Students used soapy water to test simethicone, but they could try other types of liquid, such as plain water or olive oil. How does simethicone work in these other liquids? They may need to add some detergent to produce bubbles.

Credits

Teisha Rowland, PhD, Science Buddies
Sponsored by a generous grant from Amgen