The Dirt on Soil
Author: Joyce Brumberger
Through hands-on exploration, students will learn about three basic soil types and some of their physical properties. Concepts of porosity and permeability will be developed through experimentation. Students will design and implement a model of a water treatment plant.
What should students know as a result of this lesson?
- Soil particle size and shape are a function of the amount of weathering they have undergone
- The terms porosity and permeability
- Factors that affect porosity and permeability
- How soil filters water
- The basic concept of an aquifer
- The process of water purification in a water treatment plant
What should the students be able to do as a result of this lesson?
- describe and illustrate a soil profile
- describe factors that affect water quality of groundwater
- design and build a model of a water treatment plant
- Refer to Edible Dirt Recipes
- Plastic teaspoons
- Small plastic cups
Preparation for Engagement:
- Prepare flower pot by following the directions for Edible Dirt.
- Poster size writing paper and markers
- Soil Exploration Worksheets
- 6 large plastic bins
- Small shovels or scoops
- 2 L bottles - 1 set of 3 bottles with caps for each group and 1 set for demonstration table
- 1 L bottle or pouring container - 1 for each group
- Sandwich zip lock baggies
- Magnifying glasses - 1 for each participant or set of partners
- Soil samples of sand, silt, and clay. "Play sand" can be purchased at a home improvement store in the garden section. Silt and clay can be purchased through a catalog company such as Ward's Natural Science (,a href="www.wardsci.com">www.wardsci.com)
- 8 oz. or larger, clear plastic cups - 1 for each group
- 100 mL graduated cylinder, 1 for each group
- 400 mL beakers, 1 set of 3 for each group
- Ring stands - 1 set of 3 for each group and 1 set for demonstration table
- Ring clamps - 1 set of 3 for each group and 1 set for demonstration table
- Stopwatch - 1 for each group
- Paper towels
- Landscaping marble chips - enough to fill a 2 L bottle 1/3 full.
- Pebbles - enough to fill a 2 L bottle 1/3 full. Marble chips and pebbles can be purchased in the garden section of a home improvement store.
- Aquarium gravel - enough to fill a 2 L bottle 1/3 full. Aquarium gravel can be purchased at a pet store or in the pet section of Walmart, K-Mart, or Target.
- Soil sample from backyard or other source
- Screen mesh (cut into 3"x 3" squares) - can be purchased in lengths at a home improvement store where screen is used to repair screen windows
- Craft sticks for stirring
- White paper or card stock
- Food color dropping bottles, one for each group
- Film canisters or condiment cups - 1 per group
- Alum (about 8 oz.) - can be purchased at the local pharmacy. Ask the pharmacist as it is stored behind the pharmacy desk
- Activated charcoal (1 bag) - This can be purchased at the same stores as aquarium gravel
- Computer to show downloaded video from the Internet
- Dropping bottles containing diluted bleach solution (used to simulate chlorine in water treatment plant)
Preparation for Exploration:
- Empty soils into large plastic bins, one soil sample type per bin
- Prepare sets of soil samples for each group by scooping soils into zip lock baggies and labeling. Each group should have a set containing sand, silt, and clay.
- Remove 2-3 inches off the bottom of all 2-L soda bottles with scissors.
- Prepare three 2-L soda bottles by inverting them spout side down into a ring clamp attached to a ring stand. Place a screen mesh piece at the bottom of each one and insure that the bottle caps are secure. Fill one bottle 1/3-1/2 full of marble chips. Repeat with the other two bottles, one containing small pebbles and the other aquarium gravel.
- Soil quantities for each group's set of bottles can either be pre-bagged or representatives from each group can fill the bottles at a station containing bins of soil.
- Fill one liter containers or pitchers with water, one for each group.
- Prepare "dirty water" by filling an 8 oz. clear plastic cup 1/3 full of backyard dirt. Include leafy matter and small sticks. Fill the cup with water allowing one inch of space to remain at the top and add a craft stick for stirring.
- Set up a station with containers where water filtered through the soil samples can be emptied.
- Set up a station with 3 large bins where wet soil samples can be emptied and later dried.
Preparation for Elaboration:
- Fill small containers with alum and label. Film canisters or condiment cups work well.
- Prepare zip lock bags of sand for each group that would fill approximately 1/3 of a 2-L soda bottle.
- Prepare zip lock bags of activated charcoal for each group that would fill 2" of a 2-L bottle.
- Cut screen mesh into 3" x 3" squares
- Prepare small dropping bottles of very dilute bleach that are labeled "decontaminant", one for each group.
- Prepare "dirty" water samples as described above.
- Prepare a box or bin for each group that contains the following:
- Ring stand and ring clamp
- Cut off 2-L bottle with cap
- Small 3" x 3"screen mesh pieces for bottom of container and screening floating particles
- Bag of sand
- Bag of activated charcoal
- Container of alum
- Decontaminant dropping bottle
- Plastic teaspoon
- Dropping bottle of food coloring
- White paper or stock card
- Paper towels
- 400 mL beaker
- Set up station to empty sand and activated charcoal.
The teacher welcomes students to class and begins taking attendance. While doing so, she interrupts herself by saying that she is really hungry and needs to eat. With that, she begins dramatically searching for a spoon, previously placed somewhere, all the while lamenting of her hunger. She then approaches a potted flower sitting on a desk or window sill. She picks it up and begins eating the "dirt" (see preparation instructions) reveling in how delicious it is. She responds to the comments of shock and surprise of participants and invites them to have some "dirt" too. She scoops out "dirt" into small cups and provides spoons for all to share. (This could also be prepared ahead of time and placed out of sight.)
Assessment: Assessment is on going as participants respond orally during the Engagement phase.
Exploration Part 1
- On a sheet of paper, brainstorm individually about everything and anything you know about soil.
- Share your ideas in a small group of four and create a collective list for discussion with the whole class.
- Using a magnifying glass examine three soil types: sand, silt, and clay and record your observations on the worksheet.
- Note: For the texture test, wet your forefinger by dipping it in a small cup of water before feeling the dry soil sample.
- Observe the model soil samples in the front of the room. Determine which model represents the soil type you have been observing. Record your answers in the soil column on your worksheet.
Exploration Part 2
- Brainstorm in your group to determine if particle size of soil has any important significance and record your answers on the poster size paper provided by your teacher.
- Choose one member from your group to observe the three bins of "soil" particles in the front of the room and have him or her draw a picture that illustrates the space between particles on the worksheet.
- Everyone in the group should refer to the drawing of the chosen member to illustrate the particle spaces on their worksheets.
- Each group will set up three rings stands with a ring holder and insert one cutoff 2 L bottle in each ring with the spout end down.
- Place a small screen mesh in the bottom of inverted bottle and insure that the cap is on securely, but not too tight.
- Fill each soda bottle one third full of soil; one soil type for each bottle. Be sure the levels are equal.
- Place a 400 mL beaker under each bottle.
- BEFORE adding the water, practice taking the bottle cap on and off. It is important to try and recap the bottle as quickly as possible.
- In each group of four students, one student will be the time keeper; one student will slowly pour 250 mL of water into the column of sand; one student will slowly pour 250 mL into the column of silt; and one student will slowly pour 250 mL into the column of clay. The students will simultaneously pour the 250 mL of water into the three soil columns.
- The timekeeper will announce when it is time for all three bottle caps to be removed at the same time. He or she will then start the stopwatch and announce time intervals such that the caps can be replaced at the one minute mark.
- Measure the volume of water in each beaker by pouring the water into the graduated cylinder. This should be done for each beaker and emptied in a designated area before measuring the next beaker. Record your answers on the worksheet.
- Once every group has reported its findings to the class, determine the average flow rate for each soil type. Record your answers on the worksheet.
- Empty bottles of soil into labeled plastic bins. Bottles should be wiped clean over the bins or garbage pail with a paper towel. DO NOT RINSE in sink. Clean work area.
Exploration Part 3
- Brainstorm within your group and illustrate on a large sheet of paper what you think a soil profile in nature would look like down to the bedrock.
- Stir a cup of "dirty water" for 30 seconds and allow it to settle for 3 minutes. Illustrate the contents of the cup after 3 minutes on your worksheet.
- Working with your group, illustrate a soil column that would best cleanse the dirty water. You may use a combination of soil types but the column should represent what is found in nature. Draw your groups soil column on your worksheet.
- Put the screen mesh at the bottom of each 2-L soda bottle and then add layers of soil, as determined by the group, until the bottle is 1/3 full.
- Put a white card or sheet of paper behind the dirty water and rate its clarity from 1 to 5: 1 is clear, 5 is opaque. Record results.
- Pour the dirty water into the soil column and allow it to flow through the column for three minutes into a clean beaker placed under the spout. Wipe the dirty water container clean and dry with a paper towel.
- Cap the bottle and pour the water in the beaker back into the clean "dirty water" container.
- Rate the clarity of the water using white card or paper and the scaling system in step 5. Record results.
- Predict if the experiment was repeated with dirty water containing drops of food coloring if the soil would filter out the coloring. Record answer your answer on the worksheet.
- Repeat steps 6-8 with another sample of dirty water that has been tinted with food coloring. Record results.
- Clean work area being sure not to dispose of soil down the sink.
Assessment: Assessment is ongoing as students record and illustrate observations and ideas as well as respond orally during the Exploration phase.
Ask students to respond to the following questions and discuss their answers:
- Where does soil come from? - Soil comes from the weathering of rock. Rock is weathered from sun, rain, ice, wind, running water, and other factors.
- Describe the size, shape, and texture of each of the soil types. - The sand particles were the largest and were the most angular. They felt gritty. The silt and clay were very small and their shapes were almost impossible to determine. They felt very soft and smooth.
- What do the sizes and shapes of the different soil types tell you about how much they were weathered? - Larger pieces are weathered less than the smaller ones and they have more angles. Smaller particles are more rounded, which indicates they were rolled and tumbled more and broke into smaller pieces.
- What did you notice about the spaces between particles when observing the soil models of marble chips, pebbles, and aquarium gravel? - The spaces between the marble chips looked larger than the aquarium gravel. The percentage of space in the total volume of the soil is called porosity.
- What factors do you think would affect how well water could travel through soil? - The size of the spaces between particles and how well the spaces are interconnected. If spaces are blocked then it will be more difficult for water to flow.
- Which soil sample produced the least volume of water in one minute? - Answers will likely be clay though silt may also produce the same volume of water based on the allotted time.
- What might be a reason for the differences in permeability, rate at which the water flows through the soil, for the various soil types? - The amount of space between the particles and how packed the spaces are. The smaller particles became more compacted when the water passed through them and reduced the connection between spaces.
- Different plants need different types of soil to grow. If you had a plant that required a lot of water and you had a very sandy soil, what could you do to the soil to increase its ability to hold water? - Mix the sand with some silt or clay so that the spaces between the sand particles would be smaller. It would require a little experimenting to determine how much silt or clay to use.
- Can nature "clean" water? - When dirty water percolated through the soil column it came out clearer than it was originally. When the red food coloring was added to the dirty water in the second experiment, the red dye came out with the water. Nature may be able to clean some water but there are other factors that have to be considered.
- What did the red food coloring represent in the second "dirty water" experiment? - The red dye represented chemicals and other contaminants that the soil could not filter out. Sometimes contaminates are in the soil and clean rainwater filtering through the contaminated soil picks up the contaminants and collects in the groundwater below.
Assessment: Assessment is ongoing as students respond to questions and ask additional questions that clarify or validate their own understanding.
- Prior to this section of the lesson, assign students to research the process by which water treatment plants process water for human consumption. Students should be encouraged to bring written notes to class.
- Play the short video downloaded from http://www.waterandwastewater.com/videos/view_video.php?viewkey=84325132fca8edcdfb40
- Provide each group of students with a bin of materials described in the Preparation for Elaboration section.
- Based on the video and their research, tell students that they are going to construct a model of a water treatment plant.
- Instruct the students of each group to collaborate and draw a diagram of the various steps in the water treatment process.
- Instruct groups to look at the materials in the bin and tell them they must use all the materials provided.
- Instruct them to indicate on their diagram where each of the provided materials will be used. (Refer to "Sample of creating a model water treatment plant" for some guidelines.)
- Ask one representative of each group to share the diagram with the entire class. Allow for positive interaction of the students in discussing the sequence of steps.
- Replay the video and allow groups to make final changes to their water treatment plant.
- Provide each group with 250 mL of dirty water and have them build and test their small scale water treatment model.
- Allow time for students to share and discuss their group's design and reasons for construction.
- Instruct students to dispose of materials in the designated areas.
Assessment: Assessment is ongoing as students record and illustrate observations and ideas as well as respond orally during the Elaboration phase.
Background knowledge of the rock cycle and weathering would be helpful but not required.
Best Teaching Practices
- Learning Cycle
- Science Process Skills
Alignment with Standards
- MS-ESS2-4 Develop a model to describe the cycling of water through Earth's systems driven by energy from the sun and the force of gravity.
- MS-ETS1-1 Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.
Common Core Standards:
- RST.6-8.1 Cite specific textual evidence to support analysis of science and technical texts.
- RST.6-8.3 Follow preciesly a multistep procedure when carrying our experiments, taking measurements, or performing technical tasks.
- WHST.6-8.2 Write informative/explanatory texts, including the narration of historical events, scientific procedures/experiments, or technical processes.
- Grades 5-8 Content Standard D
- Grades 5-8 Content Standard E
- Grades 5-8 Content Standard F
- Grades 5-8 Earth and Space Sciences Benchmark C
- Grades 5-8 Science and Technology Benchmark A
- Grades 5-8 Scientific Inquiry Benchmark A
Soil is a result of the weathering of rocks. Different types of soil and the minerals they contain are a result of the type of rock from which they originated. The more the rock has been weathered, the smaller the particle size and the rounder the particle shape. A soil profile may contain a layer of organic material at the top. As the profile extends downward, particle size INCREASES. These materials are least weathered. Water permeates through soils at varying rates based on their porosity, the percentage of space between packed particles, and how those spaces are interconnected.
Eventually, water reaches the bedrock, which varies in depth from region to region, and begins to accumulate. This accumulation of water is called an aquifer. The layers of water with pore spaces filled with water is called the saturated layer and the region above where the pore spaces contain air is the unsaturated layer. The zone between the saturated and unsaturated layers is referred to as the water table. The water table fluctuates based on environmental conditions and human consumption.
Water quality of the aquifer varies based on the quality of the water that initially percolated through the soil, contaminates in the soil, as well as many other factors.
- All soil samples can be collected in bins, dried, and reused
- Soil should not be washed down the sink drains
- Water can be disposed of outside
As our nation becomes more cognizant of the environment, there is a greater effort today to go "green". To support that effort, it is important for individuals to be knowledgeable in how nature takes care of itself. Water is precious and the cycle by which it travels from the atmosphere, biosphere, and lithosphere impacts all life on Earth.
The focus of this lesson is to begin to look at water as it reaches the Earth's surface and how it collects in the layers below. It is these pockets of water that most populations depend for their drinking water and daily activities. Studying the natural flow of nature helps provide understanding so that man can use materials and technology in ways that reduces his impact on the environment - "going green".
Grouping Suggestions Try to insure that all students have participated and expressed their ideas either verbally or through written comments. When working in pairs or groups try to make the groups as heterogeneous as possible being sensitive to specific needs of individuals.
Pacing/Suggested Time: Engagement: 15 minutes; Exploration: 35 minutes each part (3 parts); Elaboration: 60 minutes
Printable PDF Worksheets
Soil Exploration Worksheets
Recipes for Edible Dirt
Sample for Creating Model Water Treatment Plant sheet