4. CHALK TALK

WHAT YOU'LL NEED: pH paper, lemon juice, distilled water, 2 equal sized pieces of chalk, 2 small containers, paper clip, masking tape, marker, measuring cup and spoon

WHAT TO DO:

1. Take the pH of the distilled water and record it.

2. Make up a solution with a pH of 3 by adding 1 and 1/2 teaspoons of lemon juice to 2/3 cup of distilled water.

3. Unbend a paper clip, and then use it to carve a line in one piece of chalk. Place the chalk in one container and add enough acid solution to cover the chalk. Observe and record what happens, and then label this container "A" for acid.

4. Carve an identical line in the other piece of chalk, and then place it in the other container. Add enough distilled water to cover the chalk. Observe and record what happens, and then label this container "W."

5. Let the chalk remain in the solutions for 24 hours.

6. When the 24 hours are up, pour out the liquids and take a close look at each piece of chalk.

WHAT HAPPENED?
Is there any difference between the two pieces of chalk? Explain your answer.

THINK ABOUT IT
Many statues and buildings are made from marble. Marble is made up of the same minerals as chalk is, but it's harder than chalk. Using the results of this demonstration, what do you think could be happening to marble statues and buildings that are located in areas where acid rain falls?

5. SOIL STUFF

WHAT YOU'LL NEED: sample of soil from your area, potting soil, sphagnum moss, paper, vinegar, distilled water, measuring cup, large container, pH paper

WHAT TO DO:

1. Make up a solution with a pH of about 3 by adding 1 cup of vinegar to 3 cups distilled water. Record the pH.

2. Put a piece of filter paper into a funnel, and then fill the funnel about two-thirds full with the sphagnum moss.

3. Put the funnel over a large container, and then pour the acidic solution into the funnel (make sure you don't add too much liquid all at once). Wait until all the liquid has collected in the container below the funnel.

4. Take the pH of the liquid that collects in the container.

5. After rinsing out the funnel and container and removing the used filter paper, repeat the experiment twice using potting soil instead of sphagnum moss and then using the soil from your area. (Be sure to rinse the equipment between uses.)

WHAT HAPPENED?
Did the pH of the liquid change after you poured it through the sphagnum moss? The potting soil? The soil from your area?

THINK ABOUT IT
Based on your results, what do you think would happen if you added a small amount of lime to the soil from your area, and then poured some of the acidic solution through it? In some areas where acid rain falls, lakes and streams don't show the effects of acid rain. But in other areas where acid rain falls, lakes and streams have become acidified. Based on the results of this demonstration, why do you think these differences exist?

6. BACK TO BASICS

WHAT YOU'LL NEED:
tap water, pH paper, container, vinegar, measuring spoon, baking soda, powdered lime, vinegar or lemon piece, distilled water

WHAT TO DO:

1. Put some tap water in a container and measure the pH.

2. Add a small amount of vinegar to the water and measure the pH again. Keep adding vinegar until the solution has a pH of 4.

3. What could you do to return the pH of the water to its original pH? (Think about the substances you tested in demonstration 1.) Your goal is to ''fix'' the pH by adding only a small amount of one substance.

WHAT HAPPENED?
Did your experiment successfully return the solution to its original pH? Describe what you did.

THINK ABOUT IT
Using the results of this demonstration, what are some steps you might take to decrease the acidity in an acidic lake? What kinds of problems might this action cause?