Name ___________________________ _________
Class ___________________ Date _____________
Investigating the Permeability of Soils
The permeability of soils affects the way groundwater moves—or if it moves at all. Some soils
are highly permeable, while others are not. In this lab, you will determine the permeability of
various soils, and draw conclusions about their effect on the movement of water underground.
Problem How does the permeability of soil affect its ability to move water?
Materials
• 100-mL graduated cylinder (2)
• Small pieces of cotton
• Samples of coarse sand, fine gravel, and coarse gravel
• 3 small funnels
• Clock or watch with a second hand
Skills: Observing, Measuring, Comparing and Contrasting, Analyzing Data,
Interpreting Data
Objective: To demonstrate the effects of particle size on permeability by measuring the
amount of water which exited each cylinder and calculating the percentage of water
each sample retained, as well as the rate of drainage.
Pre-Lab Discussion
Read the entire investigation. Then work with a partner(s) to answer the following
questions.
1. Connecting Concepts: Define porosity and permeability. How do they compare?
2. Inferring: Which sample do you think will be the most permeable, or drain most
quickly? Which sample do you think will drain most slowly? Explain your reasoning.
Procedure
1. Place a small, clean piece of cotton in the neck of the funnel. Fill the funnel above the
cotton with coarse sand. Fill the funnel about two thirds of the way.
2. Pour water into the graduated cylinder until it reaches the 50-mL mark.
3. With the bottom of the funnel over another graduated cylinder, pour the water from
the graduated cylinder slowly into the sand in the funnel.
4. In the Data Table, keep track of the time from the second you start to pour the water
into the funnel. Measure the amount of time that it takes the water to drain through the
funnel filled with coarse sand.
5. Record the time (measure the time in seconds) it takes for the water to drain through
the sand, in the Data Table.
6. Empty and clean the measuring cylinder, funnel, and beaker.
7. Repeat Steps 1 through 7, first using fine gravel, and then using coarse gravel.
Time Needed for Water
to Drain Through Funnel
Water Collected in
Beaker (mL)
Coarse Sand
Fine Grained
Gravel
Coarse Grained
Gravel
Analyze and Conclude
1. Comparing and Contrasting: Of the three materials you tested, which has the
greatest permeability? Which had the least permeability?
2. Analyzing Data: Why were different amounts of water recovered in the beaker for
each material tested?
3. Interpreting Data: What effect would the differences you observed in this lab have
on the movement of groundwater through different soils?
4. Calculating: Calculate the percentage of water retained by each sample by
subtracting the amount of water drained into the graduated cylinder from the 50 mL of
water originally added. Divide this difference by the original 50 mL to find the decimal
amount, then multiply by 100 to obtain the percentage:
Retention (%) = Volume of Water Added – Volume of Water in Graduated Cylinder
Total Volume of Water Added
Drainage Rate = For each sample, divide the number of milliliters of water that drained
by the number of seconds it took for it to drain. This will give you a drainage rate in
milliliters per second. A larger number indicates a faster drainage rate.
Sample
Drainage Time
Volume of Water
Retention (%)
Drainage Rate
Coarse Sand
Fine Grained
Gravel
Coarse Grained
Gravel
5. Inferring: Based upon your result which sample do you believe would be best for an
aquifer? Explain why you believe the sample you selected would be best.