Now that Christmas is over, use the red leaves from a poinsettia plant to do an easy after-Christmas chemistry science project! In this experiment, you'll make pH test strips from poinsettia leaves and use them to discover acids and bases.
Like red cabbage (which can also be boiled to make pH test strips), poinsettia leaves contain a chemical pigment called anythocyanin. It's responsible for giving poinsettia leaves their deep red color. It's also behind the color of red cabbage, blueberries, and the fall colors of some leaves. Anthocyanin is also pH sensitive, which is why we can use it to make test strips.
Remember that the pH scale allows us to measure how acidic or basic a solution is. Many varieties of pH test strips are commercially available, but some plants contain chemicals that can be used to make your own pH test strips! With these poinsettia strips, acids will turn the pigments in the indicator to am orange or reddish color. Bases will turn the pigments in the poinsettia pH strips yellow-green, blue or purple. Neutral substances will show no change on the test strip.
Follow the steps in this project that accompanies the red cabbage pH test strip experiment to use your poinsettia strips to compare solutions for acidity and alkalinity (basicity). And read this article about acids and bases.