These gases combine with the moisture in the clouds and fall back to the ground not as clean rain but as acid rain. The acid in the water is harmful to plants, water systems, such as lakes and rivers, and animals such as salamanders and frogs. In eastern Europe, acid rain has actually destroyed forests. It also pollutes the water that humans and other animals drink. Litmus is a dye made from plants called lichens.
Litmus paper turns red in acidic solutions and blue in basic solutions.
Using litmus paper, you will be able to determine if acid rain is a threat to the frogs that live in your backyards. Check the rain-collection jar after the next rainstorm. Dip a strip of litmus paper into the rainwater. Discuss the results of your experiment with the students. Have the students repeat the same experiment at home and record their results.