Hands-on Activity How Full is Full?

Learning Objectives

After this activity, students should be able to:

• Make predictions and use appropriate tools to conduct an investigation of soil sample porosity and permeability.
• Use data based on observations to determine scientific relationships of soil and groundwater.
• Compare data collected in the lab to what happens in nature.
• Explain why engineers need to measure the porosity and permeability of different soils.

Educational Standards

Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.

All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).

In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

NGSS: Next Generation Science Standards - Science

Common Core State Standards - Math

International Technology and Engineering Educators Association - Technology

State Standards

Materials List

Each group will need:

• 2 paper cups (one with a hole in the bottom, and one without)
• 2 – 5 different types of soils (with varying grain sizes), labeled Sample 1, Sample 2, etc. (Note: write on a popsicle stick and stand it up in the dirt or affix a sticker to the outside of the cup.)
• access to water (faucet or pitcher/jug of water)
• large beaker or other type of container to collect water
• graduated cylinder or measuring cup
• large waste container for wet soil
• stopwatch
• plastic spoon or other utensil for scraping
• safety goggles, one per student
• 1 copy of the Porosity and Permeability Worksheet

Worksheets and Attachments

Pre-Req Knowledge

Some knowledge of multiplication and division.

Introduction/Motivation

(Show students a full cup of soil.) Do you think we could add anything else to the cup? The answer is yes, we could. Quite a bit of space exists between each of the grains (filled with air now); these spaces are called pores. We could add water to the soil to fill in the pores. Essentially, this is what happens when it rains. Have you ever noticed the difference between really dry soil on a hot day and the same soil after it has rained? What is the soil like when it is wet? (Answer: Soggy, damp, etc.) Does the soil take up more space? No, because the water flows through the pores of the soil.

How do you think you could measure the volume of the pores in the soil? (Most students will think of pouring water into the cup and measuring how much water fits into the cup.) The ratio of the volume of pores to the total volume the soil fills (pores plus soil grains) is called the porosity. Permeability is the measurement of how easily water flows through soil and is related to the porosity.

Engineers need to find the porosity and permeability of a soil to know where to place a well for bringing up groundwater from an aquifer for drinking water. They also need to develop technologies for drinking water systems to filter harmful germs and chemical spills. Even though a harmful spill may not occur right over a drinking water source, porosity and permeability allows the contaminants to travel through various soils into an aquifer. Today, we are going to find the porosity and permeability of different soil samples and use this information to understand groundwater flow.

Procedure

Before the Activity

• Gather materials and make copies of the Porosity and Permeability Worksheet (one per group).
• Set up lab stations: one station for each student group in an area of the classroom that will not be damaged if the area gets a little wet or dirty. If there is not space for separate lab stations, then students can conduct experiment at their seats.
• If following the traditional procedures lab, use the tip of a pencil to poke a small hole in the bottom of one paper cup per group (holes should be roughly the same size for each group).

Note: This lab is written both as an inquiry-based project and a traditional procedures-led lab. Instructions for both methods are provided below.

With the Students

1. Write the purpose of the activity on the board:

• Purpose: To study the characteristics of different kinds of soil by measuring pore space and permeability.

2. Review groundwater flow, aquifers, porosity and permeability with students (see Introduction section).

To complete activity as an inquiry-based project:

1. Write porosity and permeability on the board as vocabulary terms and define each.

• The porosity of a material is a measurement of how much of its volume is open space (also called pore space). Porosity is usually expressed as a percentage of the material's total volume. The permeability is a measurement of how easily liquid flows through a material (or soil).

2. On the board, list the following materials that will be available to the students:

• 2 paper cups (1 with a hole and 1 without a hole in the bottom)
• graduated cylinder
• large jar
• soil samples
• spoon/scraper
• stopwatch or other timing device

3. Ask students how they think porosity and permeability are related. Ask them how they would set up an experiment to test the porosity of a soil.
4. Ask the students what types of measurements they would need to be able to find the porosity of the soil. (Answer: Lead them towards volume: volume of soil, volume of water.) What measurements would they need for permeability? (Answer: Lead them towards time, volume.)
5. Have students pose different questions about the different soil samples and their porosity or permeability; write these questions on the board. (Example: What would you like to learn about these soil samples?)
6. Have students break into groups and report to their labs stations (or designated lab area).
7. Pass out materials or have students gather materials from a designated area.
8. Instruct student groups to pick or come up with a question that they would like to answer about the porosity or permeability of the soils.
9. Have them record a hypothesis/prediction in their lab notebooks or on a piece of paper.
10. Ask students to record sample number, porosity and permeability in the Data Table on their Porosity and Permeability Worksheet as well as any other measurements they need during this activity.
11. For students that are struggling, ask them to think about how they could use the given materials to measure the volume of water in a soil. Would they use a known volume of soil and water? Porosity is a percentage of pore space. How would you calculate that? etc.
12. Share and discuss findings with the class.
13. Ask students to answer the following questions when they have shared all of their findings with each other.

• Which sample had the greatest porosity?
• Which sample did the water pass through most quickly? That is, which had the highest permeability?
• As an environmental engineer, where would you recommend placing a drinking water well (i.e., in which sample)? (Answer: the sample with greatest porosity)
• As an environmental engineer, which soil sample had the greatest risk of transferring harmful chemicals into a drinking water aquifer? (Answer: sample with greatest permeability)
• What factors would you consider when locating your drinking water well? (Answer: proximity to potential chemical hazards, porosity of soil, permeability of soil, other factors such as pH of soil, depth of aquifer, etc.)

To complete the activity as a traditional lab:

1. Ask students how they think porosity and permeability are related. Ask them how they would set up an experiment to test the porosity of a soil.
2. Pass out the worksheets.
3. Have them record a hypothesis/prediction on their worksheets.
4. Divide the class into groups of four students each and have teams report to their individual lab stations or designated lab area. Pass out materials or have students gather materials from a designated area.
5. Direct students to follow the steps found on the worksheet (also duplicated below):

A. Measuring Porosity of Samples

• Pour 100 mL of water into your cup and draw a line where the water comes up to. Write 100 mL in the total volume column in your Data Table on the Porosity and Permeability Worksheet. Dump out the water.
• Fill the cup to the marked line with your first soil sample.
• Using your graduated cylinder, slowly and carefully pour the water into the cup until the water reaches the top of your sample. Write the volume of water remaining in the graduated cylinder in your Data Table.
• Subtract the volume remaining from the total (original) volume of water in the cup. This is the amount of water you added to your sample. Write the volume of water added to the sample in your Data Table – this is the pore space.
• To determine the porosity of the sample, divide the pore space volume by the total volume and multiply the result by 100. Write the porosity in your Data Table. (Note: % pore space = pore space / total volume x 100)

B. Measuring Permeability of Samples

• Hold the empty cup with a hole in it over a jar or an empty cup/container. Carefully pour your sample into the cup with the hole, allowing the water to drain into the jar.
• Pour 100 mL of water into the cup with your sample. Time how long it takes from when you begin pouring until when the water drains out of the sample. Write this time down in your Data Table.

6. Repeat parts A and B for all other soil samples.
7. Have students complete their worksheets.

Assessment

Pre-Activity Assessment

Question/Answer: Lead a general discussion of porosity, permeability and groundwater. Ask students the following questions:

• What is groundwater? (Answer: water underground, that is mostly flowing very slowly through ground soil.)
• What is an aquifer? (Answer: Layer of soil or rock containing water that yields measurable water when pumped.)

Activity Embedded Assessment

Question/Answer: Ask students questions and have them raise their hands to respond. Write answers on the board and discuss as a class.

• What is porosity? (Answer: The measurement of how much pore space is in between different particles of soil.)
• How is porosity calculated? (Answer: by dividing the volume of pore space by the total volume of soil)
• What is permeability? (Answer: Permeability is how easily water flows through soil.)

Porosity and Permeability Worksheet: Have students record measurements in their data table and follow along with the activity on their worksheet. After students have finished their worksheet, have them compare answers with their peers. Review their answers to gauge their mastery of the subject.

Post-Activity Assessment

Prediction Analysis: Have students compare their initial predictions with their test results, as recorded on their worksheet. Ask the students to explain why some soils had a better permeability to water than others.

Problem Solving: As an environmental engineer, which of the following soils would you recommend as the best for placing a drinking water well? (Answer: Soil #3, since it has the highest porosity and fastest permeability. Water flows through soils with high porosity more easily.)

1. Soil with porosity of 30% and permeability of 30 seconds through 100 mL.
2. Soil with porosity of 50% and permeability of 15 seconds through 100 mL.
3. Soil with porosity of 70% and permeability of 5 seconds through 100 mL.

Drawing and Class Discussion: Have students depict their subject area knowledge gained by sketching and labeling some of the concepts or activities. For example,

• Have each group draw or graph their results of different soil porosity and permeability. Compare the groups' results as a class and discuss the validity of each drawing.

Safety Issues

• Students should follow classroom lab rules at all times.
• Students should wear safety goggles.

Troubleshooting Tips

If holes get clogged by sand, students can use a pencil to unclog the holes.

If water flows through cups too fast, have students repeat and pay more attention to start time. (Note: students may be able to avoid problem if holes are made in advance with the tip of a pencil.)

If water takes too long to flow through the hole, have students use exactly half as much water.

Activity Extensions

Have students time how long it takes to fill a gallon jug with a water tap on low then calculate the flow rate. (Note: flow rate equals volume; i.e., 1 gallon divided by time in seconds). Then calculate flow rate of a water tap on high.

Have students sample the soil from around your school and calculate the porosity of the soil.

Have students research the groundwater in your area.

Activity Scaling

• For younger students (grades 4-6), provide detailed verbal instruction for the experiment procedure and just have students calculate porosity.

References

Copyright

Contributors

Supporting Program

Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.