Learners observe a sealed container holding a clear colorless liquid. They shake the container and the fluid turns blue. When allowed to sit for a few moments, the fluid turns colorless again. Learners can repeat the cycle as many times as they wish. Learners discover that indicators, by changing color, can be used to show that a chemical reaction has taken place. Is this case, oxygen dissolved in the shaken solution reacts with the indicator. Experiment can also be done with other indicators to create other color changes (yellow to green, yellow to red, clear to pink, clear to purple).