Thursday, March 3, 2011

General Science: Plop plop fizz fizz...

This week we wrapped up our unit on acids and bases by comparing the strengths of three different brands of antacids: Tums, Gaviscon, and Rennie. We began by talking about the role hydrochloric acid plays in the stomach and how antacids treat indigestion by neutralizing this acid when it backs up up into your esophagus.

To test which brand works best the kids ground up each antacid pill into a fine powder, dissolved it in warm water, and then added it to a test tube of vinegar (our stand in for hydrochloric acid). After waiting a minute, they measured the pH. They concluded that the antacid that resulted in the pH closest to 7 was best at neutralizing the acid.

Along the way we noted several sources of error including not using pills of the same size, losing pieces of the pills as they were being ground up, and the water temperature being variable. We also made an exciting unexpected observation. Turns out that in addition to producing an acid-base reaction, adding Gaviscon solution to vinegar leaves you with an awesome slimy gel-like solid. For your average 4th grader that's up there with the inadvertent discovery of antibiotics.

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