Determining Soil pH 5-8

Determining Soil pH
For Grades 5-8

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.

5-8 Content Standards Covered

A	Science as inquiry • Abilities necessary to do scientific inquiry • Understanding about scientific inquiry
B	Physical Science • Properties and changes of properties in matter
E	Science and Technology • Abilities of technological design • Understandings about science and technology
F	Science in Personal and Social Perspectives • Science and technology in society
G	History and Nature of Science • Science as a human endeavor • Historical perspectives

Background

At an early age our taste buds indicate to us whether something we eat is sour or bitter. These characteristics of a food can be described as acidic or basic and are due to the “chemical” nature of a substance.

Some acids are rather weak and some are very strong. For example, small amounts of weak acids are found in our mouths and stomachs. These acidic solutions serve to help break down and digest the food we consume every day. A weak base is one of the major components found in dishwashing liquid and bath soap. Acids and bases are important in industry. Industrially, one of the most important acids is sulfuric acid. It is used in petroleum refining, steel processing and fertilizer production. Phosphoric and nitric acid are used in fertilizer production, too.

It is important to understand the role of the acidic or basic nature of the soils in which food crops and plants are grown. Some plants prefer acidic soils whereas others grow best in basic soil. The acidic or basic nature of the soil can even affect the color of the leaves and flowers as well as the overall health of the plant.

How do scientists or even farmers know whether the soil in which they plant seeds or young plants is basic or acidic? They can use special test paper strips or a meter to measure what is called the “pH” of the soil. Scientists devised a “pH scale” which determines whether a substance is an acid or a base. This pH scale is a numerical scale or a number line. The numbers on the scale range from 0 - 14, allowing 7 to be the mid-point. Any substance which has a pH value of less than 7 is considered an acid, and a pH value greater than 7 is a base. This leaves a pH of exactly 7 being neutral.

0 ——————7——————14
ACID———NEUTRAL———BASE

How are pH values determined? Simple. One can use a special pH paper (called Hydrion™ pH Paper or pH test paper) which, when placed in a solution, turns a specific color depending upon the pH value of the substance. The color of the test strip is matched to a color chart, which gives the pH value. A pH tester can also be used to measure the pH of soil, water, or other substances. A pH tester is an instrument that has a probe, which is inserted into a soil or liquid sample and gives a “readout” concerning the pH of the substance tested. Knowing the pH of the soil can help a farmer know what soil type is best in which to grow particular plants, vegetables, or flowers.

Procedure

Select 3 test sites; places from which you want to collect soil.
Dig approximately 6 inches down into the area and place the bottom half of the sample into the plastic bag and label according to the site.
Place one tablespoon of soil from the collection bag into a small plastic cup. Add 1/4 cup of distilled water.
Swirl the soil and water mixture three times.
Place the edge of a 2-inch piece of pH Hydrion paper into the mixture.
Observe the color change of the pH paper.
Try to match the resulting color to the colors listed on the outside of the pH Hydrion paper package.
The colors match with a correlated pH number. This number is the pH value of the soil.
If the number is less than 7, the soil has an acidic nature.
If the number is more than 7, the soil has a basic nature.
Repeat the procedure or test by gathering soil from a different area and testing.
Compare your results to see if there are any differences in the pH of different areas tested.
Sprinkle a small amount of the soil sample on a white piece of paper or on a white index card.
Using the magnifying lens, look for the shape and texture of the soil particles.
Repeat steps #11 and #12 with soil from each collection site.
Compare your results to see if there are any differences in the different soil samples.

Further Studies

Do different types of plants, trees or flowers grow in the different areas where you collected soil?
Using your school or public library or the Internet, find out what plants prefer acidic or basic soils.
Extend your soil study by testing and observing the soil samples concerning the texture and particle size by using a soil texture test kit.
Call your local plant nursery or plant store and ask about the importance of soil pH.
Find information concerning the industrial uses of acids and bases.
Using a pH meter, test the soil pH and compare this to the pH values resulting from using the pH paper.
Observe or test:
    1. Color comparison of soil samples
    2. Temperature differences among samples taken at the site
    3. Specific texture differences.

Rubric

Students know the difference between an acid and a base by definition.
Students know how to use pH hydrion paper to determine the numerical pH value.
Students understand that different soils successfully support specific plant life depending upon the pH level.
Students can successfully repeat the experiment steps.

Assessment

Orally quiz students concerning the difference between an acid and a base.
Have students list the foods they have tasted in the past, which can be categorized as either an acid or base.
Have students prepare a summary concerning the pH differences and the texture differences found in the different soil samples.
Have students design a similar experiment involving pH differences among household products or foods.

If you have an idea or other suggestions for future lesson plans, we’d like to hear from you! Send an e-mail to fsi@forestry-suppliers.com.

Required Materials and Optional Items

The following items are required to complete all the activities in this lesson plan. All items are available from Forestry Suppliers, Inc.

Required Materials	Stock Number	Optional Items	Stock Number
Soil Sample Bags (100 pk)	79147	Soil Texture Kit	77330
pH Paper	78105	pH Meter	76237
Trowel	33413
Soil Samples from multiple sites	*
One Gallon Distilled Water	*

*Furnished by teacher or students

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

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