1-19-2010: Acids and Bases Lab

Today we ventured into the acids and bases. The purpose of today’s lab was to determine through the use of indicators and pH paper whether a certain substance was an acid or a base. Students know that INDICATORS like cabbage juice, red litmus paper, and blue litmus paper will change colors in the presence of an acid or a base. In other words, INDICATORS can only help us categorize the substances into one of the two groups, and are unable to tell as the strength of the acid or the base. Therefore, a more complete analysis requires the use of a pH scale. In our science classroom, practicality calls for the use of pH paper (way less expensive) over the use of an electronic pH meter. 🙂

Here are pictures of the indicators and the pH papers we used.

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The following are pictures of several of the many substances we used. To have fun and keep the kiddos engaged, the more substances that are used and that are relatable to them is great!

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Here are the results of the tests that the students performed:

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You can definitely see the different colors of the solutions after the cabbage juice was added and the results from the Red and Blue Litmus papers as well as the pH paper held up to the pH scale.

An A-ha! moment for the kiddos was when they learned that even after mixing the cabbage juice into the solutions, they were able to do the other tests! They found our through doing that indicators do not change the chemical make-up of the solutions; so, they other tests in the same solutions were unaffected by the cabbage juice! WOWZA! 🙂

KEY TERMS: solution, acid, base, indicator, pH scale, red litmus paper, blue litmus paper, hydroxide ion, hydrogen ion, strong base, weak base, strong acid, weak acid, corrosive, H+, and OH-