High School Teacher's Guide to Craters of the Moon
Activity 4B
How Clean is Your Home?
Students conduct pH tests on the soil, surface water, and precipitation
at Craters of the Moon and at a site in their own community.
Objectives:
Students will be able to explain the use of the pH scale as a tool to
measure acidity. Based on data collected they will be able to describe
how the acidity of soil, water and precipitation at Craters of the Moon
compares to their home environment.
Duration:
1 hour in the classroom. The monument can provide water, precipitation
and soil samples upon request. Groups may also collect their own
samples while visiting the monument. This would take about 2 hours;
collecting surface water will require a trip to a stream in the north
end of the monument or a hike to Boy Scout Cave.
Materials:
Samples of soil, surface water, and precipitation from Craters of the
Moon and from home area, pH test strips or other measurement method,
paper and pencils, beakers.
Background Information:
It is the concentration of hydrogen ions (H+) that determines the
acidity of a liquid. This concentration is described using a pH scale.
The scale ranges from 0.0 (most acidic/ highest H+ concentration) to
14.0 (most basic/ lowest H+ concentration). A solution with a pH of 7.0
is neutral. The pH scale is a negative logarithmic scale in base 10.
This means that a solution with a pH of 4.0 is ten times more than
acidic than a solution with a pH of 5.0, and one hundred times more
acidic than a solution with a pH of 6.0.
Procedure:
1. For each sample you have you will need a small (100ml) beaker.
Put your samples in and label them carefully.
2. To collect a precipitation sample at home or school, cut a
plastic soda bottle in two and invert the top half so it is resting on
the lower half like a funnel. Before collecting your sample, clean and
rinse the bottle with distilled water. Make sure you keep it free of
contaminants such as insects or dirt. Set it in a spot where it will
gather rain water and test the rain water as soon as possible after
collection.
3. For very dry soil samples you will need to add moisture. Use a
neutral-pH distilled water. Always check the pH of the distilled water
before using it.
4. Test the pH of each sample and record the results on the chart
provided on the following page.
5. Is there a difference in pH between the samples from your home
and Craters of the Moon? If there is, try to explain the difference.
Are there potential sources of pollution near your home? What are the
prevailing winds?
Work Sheet
Activity
4A - 4B
http://www.nps.gov/crmo/hsg4b.htm
Last Updated: 08-May-1999