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Preparation
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It is important that your students begin to understand that soil is a mixture of mineral particles and organic matter of varying size and composition. They need a general understanding that particles and matter make up about half of the soil’s volume and that air and/or water occupy the remainder. Your students may need help in learning that a mature, fertile soil is the product of centuries of physical and chemical weathering of rock, combined with the addition and decay of plants and other organic matter. In the investigations that follow, students examine and experiment with soil, and other material samples, to gain a better understanding of what soil is. In these first investigations, your students will use their senses to investigate properties of soil and a similar natural medium, sand. The two media will be introduced with photos to show that soils often sustain abundant vegetation and sand, generally much less. This initial contrast will serve as an invitation for students to question and investigate the properties by which soil and sand differ.
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This investigation is considered generally safe to do with students. However, you must ensure that students do not allow sand or soil traces to inadvertently enter their mouths from their hands. Make sure everyone understands this from the beginning. Students should wash their hands after handling soil or sand. Please also review the investigation for your specific setting, materials, students, and conventional safety precautions.
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To introduce students to ideas about soil, they first need to realize that soil is similar to, yet different from, other materials that can be found on solid Earth’s surface. This first part of the investigation is designed to introduce them to soil as a mixture of materials and get them interested in learning more about soil. Begin by distributing copies of the photos to your students (see LAND SURFACE PHOTOGRAPHS – Copy Master 1). Ask them to describe what they see in each photo. If they notice that there are more living things, particularly plants, in two of the photos, ask them why they think this is so.
They may suggest that rainfall (climate) is a key difference, and they will be partially correct.
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After the scene is set, introduce your students to the investigation question: “In what ways are soil and sand similar and how are they different?” Tell your students that they will be investigating this question and at the end of their investigations they will be able to provide reliable answers.
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Here are some initial questions that your students can discuss, in pairs, groups and as a whole class:
Have your students report out their ideas and make a list of them. Start a list called “Questions we have about soil.” This list will provide further insights into what your students know, and also what they would like to know. By the end of the investigation, most of these questions will probably be answered. |
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