During a three-part lesson, learners make a cabbage juice pH indicator and use it to analyze the waste products of yeast after feeding them with sugar. The intent is to demonstrate how living organisms produce carbon dioxide, which is acidic and turns cabbage juice bright pink. The lesson can be used as written, that is, part of an atmosphere unit, or you can use it during physical science when teaching about chemical properties, or even a life science unit when teaching about metabolism and the processing of fuel.