Acids and Bases: What happens when H+ ions dissociate
Today was all about acids and bases. Students put on their safety goggles and gloves and investigated how scientists classify acids and bases using the pH scale. The lesson began by teaching our young scientists about the differences between acids and bases and some common examples they can find at home. We also talked about how to go about neutralizing and strong acid or base, which is especially important for cleaning up lakes contaminated by acid rain. Then we introduced the pH scale, so they understood how scientists measure the acidity or basicity of a solution.
We did a demonstration for the students and used red cabbage juice as an acid/base indicator. The dark purple color in the cabbage comes from a pigment called anthocyanin, which changes color depending on pH.
After discovering how our indicator solution works, we then tested the pH of several common substances found in every day life, including ammonia, vinegar, cola, egg whites, baking soda, borax and milk. Acids made the purple juice from the red cabbage turn bright pink, while bases made the purple juice turn green. Students assisted us in the demonstration by pipetting the solutions into the indicator. Looking at the color change, we first assessed whether the solution was an acid or base and then predicted its pH. We tested the pH of the solutions using indicator strips and compared the actual pH with the previously predicted pH. The young scientists were shocked to discover that some solutions were extremely acidic or basic and found that soda is very acidic–sugar isn’t the only reason it is bad for your teeth! And remember, a strong base is just as dangerous as a strong acid!
This is an AWESOME video about what happens to an “aluminium” coke can in a strong acid (HCl “hydrochloric acid”) and a strong base (NaOH “sodium hydroxide), the same liquids you saw today!