Palo Alto Unified School District — Science OnLine Guide
for Teachers
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Pebbles, Sand & Silt
1st Grade Earth Science Unit |
General Information
The Pebbles, Sand, and Silt unit is a Full Option Science System (FOSS)
kit created by the
Lawrence Hall of Science at the University of California, Berkeley. It is published by Britannica.
In this unit students are expected to:
- Develop a growing curiosity and interest in the physical world around them.
- Observe, describe, and sort earth materials based on properties.
- Separate earth materials by size using different techniques.
- Observe the similarities and differences in the materials in a river rock mixture: silt, sand, gravel, and small and large pebbles.
- Explore places where earth materials are found and ways that earth materials are used.
- Compare the ingredients in different soils.
- Acquire the vocabulary associated with earth materials.
- Gain early experiences that will contribute to their understanding of several pervasive themes that relate one scientific idea to another: Structure, Change, and Interaction.
Core Concepts
- Pebbles, sand and silt are earth materials defined by their particle size.
- Pebbles, sand and silt are the products of erosion from rocks.
- The hardness of two rocks can be compared by rubbing them together.
- In moving water, earth materials settle out according to size with the largest on the bottom followed by sand, silt and finally clay.
- People use earth materials for many things, such as building materials, jewelry, pottery, glass, and art materials.
- Soil is composed of earth materials as well as organic materials called humus, the decomposed remains of plant and animals life.
Misconceptions
- Many children believe that sand comes from the seafloor and is washed up onto the beaches. The rock rubbing exercise helps them understand that sand comes from rocks. The Sand Story (page 11 of the Companion Guide) may be used to help dispel this misconception. Large pebbles, gravel, and even sand are all basically the same materials-just different sizes.
- Children are fascinated to learn that many of our building materials come from the earth. They learn the importance of how earth materials are transformed to be useful in our daily lives.
- Children may use the term dirt in describing what scientists call soil. The word dirt may have negative connotations. We suggest using the word soil, carefully explaining that it is the result of natural processes and is essential for life.
