Biology: Acids and Bases

This week we started a new topic:  acids and bases.  First we used litmus paper and pH paper to classify different household liquids.  Then we boiled up some purple cabbage. Cabbage broth has the interesting property of indicating for acids and bases.

The kids added cabbage juice to the different liquids and observed the results. They recorded the color changes and using the pH values, ordered the cups according to where they fall on the scale. They observed that cabbage juice indicates strong acids with pinks, weak acids with purples, neutrals with blues, weak bases with greens, and strong bases with yellows. Finally they were given an unknown liquid, and using their cabbage-pH scale they guessed its pH.

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Biology and General Science

This week we learned about acids and bases and three types of indicators you can use to identify them. We began by using red and blue litmus paper to test different household liquids. We were then able to classify them as acids, bases, or neutral. However while litmus paper is useful, it doesn't tell you anything about how strong or weak a base or acid is. So, for example, while baking soda and bleach, the two bases we encountered, score the same on a litmus test, baking soda tastes mildly bitter whereas tasting bleach will land you in the hospital (hypothetically speaking, of course!). We observed that in order to appreciate this without landing in the hospital, pH paper comes in real handy.