Porosity

Purpose

To measure the amount of water stored in the pore space of a soil sample.

Background
Soils are made of particles of different types and sizes. The space between particles is called pore space. Pore space determines the amount of water that a given volume of soil can hold. Porosity is the percentage of the total volume of soil that consists of pore space. This is an important measurement in areas where drinking water is provided by groundwater reserves.

Key Words

Soil

Particle

Pore space

Porosity

Saturation

Groundwater

Materials

Dry soil sample or sand

Two 500 ml beakers

Water

Procedure

1. Fill one beaker, up to the 500-ml mark, with dry soil or sand. Place it on a table or flat workspace.

2. Fill the other beaker, up to the 500-ml mark, with water.

3. Slowly pour the water from the second beaker into the soil sample. Stop pouring when the water level reaches the top of the soil. The soil has reached saturation and cannot hold any more water.

4. How much water is left in the second beaker?

5. How much water is now held in the pore spaces of the soil sample?

6. Use your answer from question 5 to compute the porosity (the percentage of pore space) of the soil sample.

http://www.soest.hawaii.edu/spacegrant/class_acts/Porosity2.html