Earth Science Week Classroom Activities

No Child Left Inside Activity

Soil Properties

Grade Level: 5-10 Earth and Life Science

Activity Source: Adapted with permission from Kristen Lucke, Views of the National Parks, National Park Service.

National Park Service

 

Background

“Soil porosity” refers to the amount of pores, or open space, between soil particles. Pore spaces may be formed due to the movement of roots, worms, and insects; expanding gases trapped within these spaces by groundwater; and/or the dissolution of the soil parent material. Soil texture can also affect soil porosity

There are three main soil textures: sand, silt, and clay. Sand particles have diameters between .05 and 2.0 mm (visible to the naked eye) and are gritty to the touch. Silt is smooth and slippery to the touch when wet, and individual particles are between .002 and .05 mm in size (much smaller than those of sand). Clay is less than .002 mm in size and is sticky when wet. The differences in the size and shape of sand, silt, and clay influence the way the soil particles fit together, and thus their porosity.

Soil porosity is important for many reasons. A primary reason is that soil pores contain the groundwater that many of us drink. Another important aspect of soil porosity concerns the oxygen found within these pore spaces. All plants need oxygen for respiration, so a well-aerated soil is important for growing crops. Compaction by construction equipment or our feet can decrease soil porosity and negatively impact the ability of soil to provide oxygen and water.

Materials

  • Four 100ml graduated cylinders per group (or a measuring cup and two clear plastic bottles)
  • Fine, playground-style sand and coarse, aquarium-style gravel
  • Blank piece of paper and something to write on
  • Pencil or pen
  • Ruler
  • Metal spoon or gardening spade

Procedure

  1. Divide into small groups. On a piece of paper, make a data table like the one below for each group.
Soil particle type Volume of Water used (ml)
Gravel
Sand

  1. With each group taking four graduated cylinders, fill one cylinder with 100ml of sand, one with 100ml of gravel, and two 100ml of water.

  2. Discuss the experiment: Which substance has more pore space: gravel or sand? How did you make this decision?

  3. Have each group fill the cylinder of sand with the water (be sure to not let the water overflow). Record the amount of water used in the data table.

  4. Repeat step 4 with the gravel and the second cylinder of water.

  5. Discuss as a group what happened and why? Was your initial hypothesis accurate?

  6. Before leaving the classroom, though, refill two of the graduated cylinders with 100ml of water. You will also need paper, pens, and pencils to record observations. Draw the data table below for each group.

Survey area Volume of Water used (ml)
1
2

Find a place outside where it is permissible to collect small soil samples and have each group choose a survey area.

  1. Record observations of this survey area. Look at the types of plants growing in the soil, evidence of wildlife, etc. Is the soil in the shade or in direct sunlight? Sketch what you see.

  2. Once survey area observations have been made, obtain a small sample of soil to determine its texture. Is the soil wet or dry? If it’s wet, does it feel gritty (sand), smooth and slippery (silt), or sticky (clay)? Can you see and measure individual particles? Record all of your texture observations.

  3. Now have each group fill its empty graduated cylinder with 50ml of soil. Pour water from one graduated cylinder into the soil until water just covers the top. Record the volume of water used in the data table next to Survey Area #1.

  4. Pick a new survey area (if possible, with different vegetation). Repeat steps 3 through 5, and record the volume of water used in the data table next to Survey Area #2.

  5. Return to the classroom and discuss your results: Was there a difference in soil porosity? Were there similarities? For the soil samples with similar porosities, did they have the same soil textures? Do you think these soils provide adequate water and air for plants? What types of plants live in these soils? Do factors such as sunlight or soil texture seem to affect the porosity of the soil?

 

Standards and Connections

NGSS

  • Disciplinary Core Ideas: ESS2.A: Earth’s materials and systems; LS2.C: Ecosystem dynamics, functioning, and resilience
  • Science and Engineering Practices: Planning and carrying out investigations; Analyzing and interpreting data
  • Crosscutting Concepts: Cause and effect; Structure and function

 

Sustainability Connections

  • SDG 6: Clean water and sanitation– Soil porosity affects groundwater availability (time for aquifers to recharge) and quality (soil can filter water).

 

  • Environmental Education Group Games and Activities: Pollinator Seed Balls
    • Scroll down the page to find this activity, which has students make and scatter seed balls to encourage the growth of native plants.
    • This can be a follow-up to “Soil Properties” and can be done in area where students determined the soil has adequate porosity to support plant growth to then consider other properties of soil that make it vital for plants growth and the health of an ecosystem.
    • An extension could include revisitng the area where seed balls are distributed to observe growth and pollinators that visit the plants.