Final answer:
Jared measures foam height as it correlates to the carbon dioxide produced, which determines the rate of fermentation.
Step-by-step explanation:
Jared is measuring the amount of foam in each glass to determine the rate of fermentation. In an experiment involving fermentation, the production of carbon dioxide gas often manifests as foam due to the gas getting trapped in the liquid medium as it is released by yeast or other microorganisms breaking down sugars. This foam can be a good indicator of the level of fermentation activity, as more foam is usually correlated with higher production of carbon dioxide. By measuring the height of the foam, Jared can infer the amount of carbon dioxide produced in the process.