Acids and Bases

Pretend that blueberries are your favorite food ever, and you plant a blueberry bush in your yard. You wait an entire year anticipating fresh blueberries in the spring. Unfortunately, spring comes and goes, but no blueberries. You consult a professor in the agriculture department of a local university – because you are serious about your blueberries – and he suggests that you adjust the pH of the soil, because blueberries prefer to grow in acidic soil. So, what does that mean? To understand, you first must learn about acids and bases. Use your cursor to roll over the images below and learn more about the differences between acids and bases.

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Measuring Acids and Bases

The pH scale is a measure of how acidic or basic a solution is. The pH scale ranges from zero to fourteen. The pH number denotes the hydrogen (hydronium) ion concentration. The pOH denotes the hydroxide ion concentration. Solutions containing a higher concentration of hydronium H3O+ will have a lower pH. On the pH scale, acidic solutions have a pH value below seven. A solution with a pH of zero is very acidic. A solution with a pH of seven is neutral. Pure water has a pH of seven. Basic solutions have pH values above seven. A change of one pH unit represents a tenfold change in the acidity of the solution. For example, if one solution has a pH of one and a second solution has a pH of two, the first solution is not twice as acidic as the second; it is ten times more acidic.

Acids and Bases in Living Systems

Acids and bases are important in biology because living organisms can only tolerate small changes to pH. There are a variety of buffer systems in place in living organisms to maintain this delicate balance. In this interactivity, click on each of the image thumbnails to learn more about how pH is important to living systems. Click the player button to begin.

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Acids and Bases Review

Now that you have learned the basics of acids and bases, review your knowledge in this non-graded activity. Read each question and select the correct answer. Then, click SUBMIT to check your responses. Click the player button to get started.