Did you know that purple cabbage juice can be used to test pH? Add ten drops of it to a substance and the juice will turn red, blue, or neutral depending on the pH. Or use it to soak coffee filter paper and you can make handy-dandy pH testing strips! This week our class did both thanks to Barbara’s cabbage-wrangling.
What’s the point of all this pH testing? pH is one indicator of water quality, and soon we will start testing the pH of the water in our trout hatchery. Trout fry need water with a pH of 6.5 to 7.5 (a pH of 7 is neutral). The kids will need to know how pH works if they are going to monitor the tank conditions and keep the trout fry happy and healthy until our release date.
For their homework, kids made fantastic predictions about the pH of household liquids. It is interesting to see their initial ideas about what makes a substance basic or acidic. Ben I figured that mouthwash would be acidic, because it kills plaque (correct), and predicted that olive oil would be basic “because it is thick.” Dilan seems to have raided the refrigerator and tested lots of acids: alcohol, apple cider vinegar, even pickle juice! And Remy answered the question I think we’ve all been asking: is spit basic or acidic? If you guessed basic, you’re right (though maybe the pH of spit fluctuates over the course of a day–the jury’s still out on that).