Today was all about acids and bases. Students put on their safety goggles and investigated how scientists classify acids and bases using the pH scale. The lesson began by teaching our young scientists about ions, an atom that loses or gains an electron. Once atoms become ions and are charged, they can attract or repel each other, like magnets. This is how acids and bases react. 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, baking soda, borax and milk. Acids made the purple juice from the red cabbage turn red, while bases made the purple juice turn green. Students assisted us in the demonstration by pouring 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!
Additional Information: 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! http://www.youtube.com/watch?v=WnPrtYUKke8