Age: grades 3-6
Subject: Soils
Skills: observation, comparing, classification
Duration: 40 minutes
Group size: any
Setting: indoors
Key vocabulary: particle, sand, clay, silt, organic matter
Materials:
3 different soil samples (One with a high sand content, one with a high clay content, and one with a high organic content)
Sheets of paper
Magnifying glasses
Objectives:
The student will be able to:
1. Identify the different colors, shapes and sizes of soil particles.
2. Recognize the difference between the organic and non-organic soil particles.
3. Contrast the difference between two soil samples based on the particles contained in each.
Method:
The students will observe soil samples with a magnifying glass.
Overview
Most soils are composed of a variety of particles such as sand, clay, and organic matter. These particles are the result of rock weathering and organic material and are shaped by their transport in water, wind and ice. By spreading samples of soil out on pieces of paper and examining them with a magnifying glass, students can learn a great deal about what the soil is made of and contrast the differences between the samples. The properties of the soil particles the students will observe are color, size and shape. They will also identify the organic and non-organic particles.
Procedure
Spread the soil samples out on sheets of paper and examine them for the following:
1. Color
Dark colored soils usually indicate a high organic content. it may also indicate a poorly drained soil. A light colored soil usually indicates a high sand or clay content and a well-drained soil.
2. Size of particles
Are the particles larger or smaller than a grain of sand? Clay and silt are very small particles. Organic particles are usually large.
3. Shape of edges
The shape of the edges indicates the extent to which the particles have been worn down by various forms of erosion processes. Smooth particles indicate lots of wear, while rough, irregular particles indicate little wear.
4. Differences in the particles
How many different kinds of particles are there? What are the differences?
5. Organic matter
Is there evidence of organic matter? If there is, where would it have come from?
6. Living things
Are there living things in the soil? What are they?
Extension
1. Have younger students draw a picture of what the soil particles look like.
2. Construct a decorative soil jar, alternating layers of light and dark, and coarse and fine soils.
3. Fill a quart jar 1/2 full with equal amounts of gravel, sand and soil. Add water to within 5 cm of the jar's lip. Stir gently until well-mixed and allow the jar to sit over night. The next day, have the students draw a soil chart, identifying the particles and the order in which they settled.
4. For older students, use this activity to introduce how sails are formed from the transport of weathered material by water, ice and wind and-the accumulation of organic material. Relate the characteristics of the particles to the various processes.
Evaluation
Have the students contrast two different samples of soil based on differences in the particles.
Sources
1. Bergman, A., & Jacobsen, W. (1983) Science Activities For Children. New Jersey: Prentice-Hall Inc.
2. Sund, R., Tillery, B., & Trowbri dge, L. (1973) Elementary Science Discovery Lessons: The Earth Sciences. Boston, MA: Allyn and Bacon, Inc.