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Determining Soil pH
For Grades 9-12

Areas of Study:
Mathematics • Earth Sciences • Chemistry

Correlated to National Science Education Content Standards

Grades	A	B	C	D	E	F	G
K-4
5-8
9-12

The ideas and activities included in this Lesson Plan are intended for use in classrooms where an appreciation for a better understanding of the environmental and earth sciences is the focus of the core curriculum. It is not intended to be a substitute for a comprehensive environmental and earth sciences curriculum, but rather, complement the learning experiences of children in the recommended targeted grades indicated.

Forestry Suppliers provides this information to qualified educators as a template, or guideline, for creating an interesting and enjoyable learning experience for the intended targeted age group. Please note the alignment with National Science Education and Math Standards where applicable.

If you would like to see us develop additional Lesson Plans in other areas of environmental and earth sciences, or if you would like to contribute your own ideas and receive credit in future issues, please contact us through the Education Section of our web site at www.forestry-suppliers.com or e-mail us at fsi@forestry-suppliers.com. We’re always happy to hear from you and we’ll do everything in our power to accommodate your requests.

9-12 Content Standards Covered

Background

Many of the foods we enjoy have an acidic or basic nature. Citrus fruits contain acid, which give them a desirable tart or sour taste. Many common household products are basic in composition, such as cleaners and soaps. Weak bases found in bath soaps help create a slippery effect on surfaces; this is experienced when washing your hands. Bases have a bitter taste that we may have experienced as young children when we accidentally got a little soap solution in our mouth when we washed our face. Basic solutions are sometimes called alkaline. Acids, weak and strong, have important industrial uses. Sulfuric acid is important in petroleum refining, steel processing as well as in the process of fertilizer production. Weak acids are found in saliva and gastric juices.

Chemically, acids are defined as substances when mixed with water form hydronium ions, H3O+. Bases are defined as substances which form hydroxide ions, OH-, when mixed with water. A color reaction with a special paper (called litmus paper) physically defines a solution as acidic or basic. Blue litmus paper turns red when exposed to an acidic solution and red litmus paper turns blue when in contact with a basic solution. To more specifically define an acidic or basic substance, scientists devised a numerical scale, called a pH scale, to categorize substances as an acid or base. Numerically, the scale is from 0 to 14, with 7 being the midpoint. Any solution or substance having a pH value of less than 7 is known as an acid and above 7 is considered a base. Seven is considered neutral. A special test paper, pH Hydrion, is used to numerically measure pH. Depending on the acidic or basic nature of the test solution, the paper turns a specific color which can be matched to a standard color chart correlated with pH values. A pH meter can also be used to measure the pH of a solution or substance. The meter consists of a probe, which is placed in the solution and the meter displays a digital readout of the pH.

Agriculturally, the pH value of soil is an important factor or consideration for farmers. Particular crops and plants require a specific pH to thrive and produce high yields. The pH of the soil can even affect the color of leaves or flowers. Whether it is growing tomatoes in a small garden or soybeans over many hundreds of acres, knowing and maintaining the correct soil pH is a must. By conducting the following experimentation, one can gain a better understanding of acids and bases and how pH is measured.

Procedure

1. Select 5 different soil-testing sites; make observations of the surroundings, which may lend to the possible resulting differences in pH of the soils tested.
2. Vertically dig 6 inches into the site and place the sample retrieved at that depth into the plastic bag and label.
3. Weigh out approximately 10 grams or measure about 1 tablespoon of the soil and place into a plastic cup or beaker.\
4. Add 60 ml or 1/4 cup of distilled water.
5. Swirl the soil and water mixture 3 times; use a clean stirring rod or spoon to thoroughly mix the water and soil.
6. Place the edge of a 2-inch piece of pH Hydrion paper into the mixture.
7. Observe the color change of the pH paper.
8. Try to match the resulting color to the colors listed on the outside of the pH Hydrion paper package.
9. The colors match with a correlated pH number. This number is the pH value of the soil.
10. If the number is less than 7, the soil has an acidic nature.
11. If the number is more than 7, the soil has a basic nature.
12. Repeat the procedure or test by completing steps 3 through 11 using the other soil samples.
13. Compare your results to see if there are any differences in the pH of different areas tested.
    

Further Studies

*Furnished by teacher or students

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Forestry Suppliers’ Soil Analysis F.I.E.L.D. Kit™
Fundamental Investigation of the Environment Leading to Discovery™

If interested in soil analysis for classroom activities, consider our Forestry Suppliers’ Soil Analysis F.I.E.L.D. Kit™. Use the kit for this and many more related activities. See Further Studies section for a few ideas.

The Forestry Suppliers Soil Analysis F.I.E.L.D. Kit™ is available exclusively from Forestry Suppliers and includes some of the items used in this lesson plan, as well as additional Lesson Plans, which will involve the use of other items. All kit items may also be purchased individually. Call our Sales Department at 1-800-647-5368 or visit us on the web at www.forestry-suppliers.com.

Forestry Suppliers’ Soil Analysis F.I.E.L.D. Kit™ Contents
Stock Number 36845
Kit items may be purchased inividually.

Required For This Lesson Plan
Qty.	Description	K-4	5-8	9-12	Stock Number
1	Soil Color Chart				77365
1	Soil Texture Kit				77330
1	Keck Sand Shaker				53691
1	Soil N-P-K Kit				77960
1	Soil Thermometer				89028
1	Soil Tins				77045
1	Soil Sample Tube				76924
1	Hydrion™ pH Papers				78105

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Correlated standards reprinted with permission from National Science Education Standards. Copyright 1996 by the National Academy of Sciences.
Courtesy of the National Academy Press, Washington, D.C., www.nap.edu

LP00106 01-0041
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