Knowledge and Skills Statement
Earth and space. The student knows that the natural world includes earth materials that can be observed in systems and processes.
Demonstrated Proficiency
Ask students to bring in soil samples from home or collect samples from your schoolyard. Give them a chance to investigate the soil with a plastic spoon and a hand lens. Ask students to describe the soil and ask if they can identify different components of the soil. Ask students to describe how the soil looks and what it feels like. Students may notice that their samples have similarities and differences. Let students know that soils are made of different components such as sand and clay. Give students an opportunity to feel sand and clay powder as separate materials. Students should be able to describe sand as gritty with large particles which let water pass through easily. They should know that clay is powdery or slick feeling, very small, and does not let water pass through easily. Students should also recognize that topsoil is the top layer of the ground. Make mudshakes with the students by putting soils in a jar with water and a pinch of laundry detergent. The detergent should help the layers settle out more effectively. Once the layers settle out, students will notice that sand sinks to the bottom, clay sits on top, and other soil particulate rises to the top.
Further Explanation
In later grades, students will begin to study the properties of soil that make them valuable for different uses. The soils studied in school are sandy soil, clay soil, and loam or humus. One of the primary properties studied is how well soil retains water. The components and the particle size of soil determine how much water it will retain. Oftentimes, soils with different properties will be mixed to achieve the desired water retention levels.
Sandy soil retains the least amount of water. Sand is made of weathered rock, which does not absorb water. Therefore, when sand is mixed in the soil, it increases the drainage that occurs.
Clay soil has very fine particles, and the large quantity of particles result in water retention. Silt is clay that has been deposited around bodies of water. Silt has the finest particle size and has the same properties as clay soil.
Loam or humus are organic soils that are rich in nutrients. Organic soils have large particles. Therefore, organic soils do not retain as much water as fine-particle soil.
Supporting Information
Research
Keeley, Page. “Formative Assessment Probes: Soil and Dirt: The Same or Different?” Science and Children 52, no. 7 (2015): 29–31. http://www.jstor.org/stable/43501170.
Summary: Formative Assessments should be used to guide instruction based on results. This article explains how using a pre-assessment when teaching soil science can help guide instruction. Students often confuse the terms "dirt" and "soil" as interchangeable because they do not yet understand what soil is. Teachers should allow students to discuss soil and dirt and listen for misconceptions. When students observe fresh soil, they can see that soil is made up of living and nonliving things. Once students know what soil is, they can start learning about and describing different soil types. Students can compare different types of soil and describe their properties. This can lead to a discussion on how different soils are used in habitats and for human use. Understanding soil science can help students understand more advanced concepts later in their education.