Department of Biology


Highlight key points in the question:

Your roommate decides to try his hand at home-brewing beer. He adds baker's yeast, malt, hops, and sugar into a gallon of water. He then puts this mix into a gallon bucket without a lid. You wait to see if he will cover the bucket, but he leaves the mixture exposed to the air. "You know you'll never get any alcohol or carbonation produced like that," you advise your roommate.

"What do you mean?" He replies. "I've got the right proportions of yeast and sugar. It should start fermenting any time now."

Help your roommate, and explain why he will not get enough fermentation to produce alcohol and carbonation.

The last sentence tells you what you are supposed to do:

The other two highlighted phrases in the question are clues about why the yeast will not ferment well.

The remainder of the question is filler. Do not be distracted by extraneous details such as the measurements or the malt and hops.

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