Initial Publication Date: January 13, 2021

Chapter 2: Physical Properties of Soil and Soil Formation

Chapter Summary

To begin to understand soil, simply dig a hole! Looking at the exposed soil reveals several obvious physical aspects. Initially, you see that soil has many colors - it is not simply brown or red or black. Next, you notice patterns in the color. The upper portion of the soil is darker (browner or blacker) than the materials below, and the colors appear in horizontal bands or layers. A closer examination reveals that plant roots are more common in the upper layers. Furthermore, the soil is composed of clumps, clods, or aggregates that are made up of still smaller particles. There is also a different feel from the top layer to the bottom in terms of how easy it is to dig or break apart. These simple observations identify many of the key physical characteristics, or morphology, of soil: color, texture, structure, consistency, and horizons. Soil scientists use these characteristics to create a soil's profile description (also referred to as the soil morphology).

Learning Objectives

Students who complete this module will know and be able to:

  • Describe soil texture and color
  • Explain and use the soil triangle to characterize soil
  • Explain soil horizons

Essential Questions

  • What are the stories hidden in the soil?
  • What can soil color, structure, and texture tell us about the past?
  • What can soil color, structure, and texture tell us about the present?
  • How do soil physical properties influence our lives today?
  • How does soil form and how does its formation affect its characteristics?

Big Ideas

  • Soil characteristics determine what types of life can be supported.
  • Soil conditions can be a window into current conditions as well as a record of past events.

Additional Teaching Materials

Educators PPT file chapter 2
Click to view

Supplemental Educators PPT file for Chapter 2 (PowerPoint 2007 (.pptx) 12.3MB Feb9 21)
Click the link above to download the file to your desktop or hard drive.

Educators can purchase soil samples to use in the activities from this source: AGClassroom Soil Samples

Printable Materials

Below are the links to PDF files used in this module.

The Color of Soil
Color Changes
Winogradsky Column Protocol
Soil Texture Analysis 
Soil Triangle Practice 
Soil Texture by Feel 
Perkin through the Pores 
Rain and Soil Lab 
Soil Compaction 
State Soil Worksheet 
Soils Overview Unit 
Soil Formation Worksheet 
A Soil Profile Lab

Optional Student Worksheets for this chapter are provided below.

Student Worksheet in PDF for Chapter 2 (Acrobat (PDF) 158kB Nov7 21)
Student Worksheet in Word for Chapter 2 (Microsoft Word 2007 (.docx) 146kB Nov7 21)

Teaching Notes and Tips

Students discover the clues to a mystery hidden in the soil. They explore the physical properties of soil, and how soil formation determines these properties. Students then examine how soil characteristics influence the range of plants that can grow in a given region.

Time required : 650 minutes, or 10-11 class periods
Tools and Technology needed: Computer for video clip, a variety of soil samples, pint- and quart-sized mason jars, lab materials, stopwatch, ice pick, tin can with ends cut out, scale, light microscope.

In this module exploring the physical properties of soil, students complete a variety of activities and labs. Before beginning the module read through the lessons, and acquire needed materials and technology. Print out any handouts that will be needed. In order to reduce the amount of time needed in the classroom, some activities can be assigned as homework or made optional.

This module includes many hands-on activities and labs. To save time and materials the labs can be set up as stations and rotated through by lab teams. Alternately educators may choose to have student "experts" practice the labs and demonstrate them to the rest of the class. Some labs are conducted outdoors, which may not be possible for all educational settings. Several virtual labs require Flash animation which does not operate on tablets nor all types of computers. These labs can be made optional.

Download and print out a variety of State Soil booklets for students to explore.

Science Standards (NGSS)

Performance Expectations

HS ESS2-2
HS ESS2-5
HS LS2-1
HS LS2-5
HS PS1-2



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