Main objective:
Students will be able to measure the pH of soil and natural bodies of water
Materials:
Apron, Gloves, goggles, collected soil samples, collected water samples, small plastic measuring cups, 1 pipet, pH paper strips, wax pencil
Instructional input:
Adapted from Neo Science: simulating the effects of acid rain
This activity works well with groups of 2 or 3
Prior to the investigation students are to collects three water samples from various locations such as a pond, river, creek, lake or even rainwater. Students may collect the water samples in small jars. In addition students will collect a small soil sample form the same area and place this in a zipper bag. The students must label the sample locations accurately. Have students collect from different locations so that there is a wide range of pH and buffering capacities. Granite rocks have little or no buffering capacity, whereas limestone or soils with a high calcium carbonate content have a high buffering capacity.
Procedure:
pH of water
1.Using a wax pencil, have students label the measuring cups with the locations from which the water samples were collected.
2.Using a pipet, students should carefully transfer 4 - 5 ml of each water sample into the corresponding cup. (Be sure to have the students rinse the pipet in distilled water after each transfer to avoid contamination.)
3.Provide students with the pH test strips and have them dip the end into the water for about 2 seconds, carefully shake off any excess water and compare the color that appears to the color on the pH indicator chart. Have students record the pH and other observations in a data table A.
4.Students will repeat step three with the remaining water samples they have collected.
Data table A
|
Water sample number
|
Water sample location
|
pH of sample
|
Comments or observations
|
1
2
3
Procedure:
pH of soil
1.Students should place about 2 tablespoons of the first soil in a plastic cup containing distilled water.
2.Have the students allow the particles to settle for 15 - 20 minutes
3.Have students pipet about 5 ml of the top layer of water into a measuring cup.
4.The students should use the pH test strips to determine the pH of the soil sample. Record the data in table B
5.Repeat steps 1 - 4 with remaining soil samples
Data table B
|
Soil sample
|
Soil sample location
|
Soil description or makeup (limestone, granite etc.)
|
pH of sample
|
Comments or observations
|
1
2
3
Students should write up a lab report according to the scientific method. They should include a statement of the problem, hypothesis, procedure (including dependent and independent variables and a control), data, conclusions and validity.
