While acids and bases are often a main part of a study of chemistry, they also play a very important role in the survival of living systems. For example, if a small lake is impacted by acid rain, the water may become too acidic for the fish to live. Since the system is closed, the fish would not be able to move to a better environment. Also, human blood is very sensitive to changes in acidity, staying slightly basic at 7.2 on the pH scale. A large change in blood acidity can cause death.

The acidity of substances is measured on the pH scale (which stands for percent hydrogen). The more hydrogen present, the more acidic something is. The less hydrogen, the more hydroxide it has, the more basic it will be. The scale ranges from 0 - 14.

In order for living systems to return to normal, they must introduce something called a buffer to change the pH level. A buffer can make an acidic environment more basic (such as adding lime to soil) or make a basic one more acidic. Nature has built-in buffers, but many times people need to get involved to rescue a particular environment.

Answer the practice questions and then watch the videos to learn more about acids, bases, and pH.