Material Porosity Experiment

Environmental Geology, GLG110, Fall 2006

Due Tuesday, November 14^th

Purpose: to test how certain earth materials hold, release, and store water differently.

Materials:

• Three plastic cups
• Tap water
• Gravel (>2mm), sand (<2mm), dirt (~50% organic material mixed with ~50% sand or mud), and clay or finest material possible

Tasks:

1. Read the steps below before performing.
2. Obtain three clear plastic cups from your professor, or use the cups from the last experiment. The volume of this cup is ______ milliliters.
3. Fill one cup with one of the four materials (gravel, sand, and dirt) to about half full. Do gravel first, sand second, dirt third, and clay (if you have) sample last for the following steps.
4. Compact the sediment in a cup (no holes in the bottom) with your fingers until you cannot compact it anymore. This represents natural compaction of sediment on natural surfaces.
5. Fill the other cup with normal cold temperature tap water. You will have to graduate your cup to the nearest 10 ml so you know how much water it takes to fill the sediment full of water.
6. Pour the water into the other cup, but not so fast that it erodes a hole in the top of your sediment, until water is filled up to the top of the sediment. Measure how much water you poured into the sediment cup by subtracting from the known amount you had in the source-water cup. Record your data and complete the math to determine the porosity of the material.
7. For the other cup, use and ice pick type tool and make about 20 holes (not slices) in the bottom of one cup, each hole being about 1/8^th inch in diameter.
8. Dump the sediment water mix from the first cup into the cup with the holes and collect the water that comes out with the last cup. When water has finished draining out of the sediment/water mix, measure how much water came out. Record in your data table and complete the math.
9. Redo the previous steps for the other materials and complete your table below. And bring to class on Tuesday for a class discussion of your data.

Name __________________ Date _________

Data Table for Porosity and Water Retention in Different Materials

Type of Material	Volume of sediment (milliliters)	Volume of water used to fill water to top of sediment (ml)	Percent porosity of sediment [(ml water ÷ ml sediment] * 100%)	Volume of water drained from sediment (ml)	Volume of water remaining in sediment (ml)	Percent of water retained in sediment (water drained ÷ water remained)*100%	Notes
Example	240	40	17%	15	25	60%	Color of water dark brown when retaining. Method was controlled well.
Gravel
Sand
Dirt/Sand Mix
Clay

Answer the following questions on the next page.

List and state one hypothesis before performing one experiment:

Explain the difference, if any, between your hypothesis and the results:

What did you like about this experiment?

Where there any difficulties while performing this experiment?