An Introduction to Acids and Bases
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Therese Tobecksen Saint Andrew the Apostle
331 155th Place
Calumet City, Illinois 60409
1. Primary students will review the concept of sorting objects by various
2. Students will sort Lego blocks by size, color, shape, number of "bumps",
3. Students will classify household liquids as bases or acids by using
cabbage-juice paper and then litmus paper.
Assorted Lego blocks, a purple cabbage, cabbage-juice indicator paper (prepared
at home by soaking half a cabbage in boiling water and then dipping and drying
coffee filters), litmus paper, orange juice, vinegar, cola, liquid soap, baking
soda in water, Pepto-Bismol and small plastic or paper cups.
Ask students how they could sort a collection of Lego blocks. Discuss how to
sort them by size, color, shape, etc. Mention other items which are sorted such
as: items in a grocery store, items in their desk, the animal classification
Show a half head of purple cabbage. Explain that the other half had been soaked
in boiling water and that the juice it made was used to soak coffee filter
papers which they will now use as a "sorter" or indicator.
Reveal and identify household liquids which will be sorted. Send students to
lab stations which have been set up with cups containing about a quarter cup of
the various liquids.
Let the students try to discover that the cabbage indicator will turn green or
pink. Discuss some of the characteristics of acids and bases. Try to have
them conclude that green indicates a base and pink indicates an acid. Repeat
the procedure using litmus paper.
Discuss some everyday situations involving acids and bases such as the use of
vinegar to clean a coffee pot or tea kettle, swimming pool chemicals, acid rain,