In this demonstration students will see what porosity is by observing the filling of pore space by a liquid. Fill one jar completely with marbles. Keep bottle of colored water hidden until ready to use. Procedure Introduce the concept of oil reservoirs. Oil is found naturally in porous sedimentary rocks.
Porosity is the space around the mineral grains that make up the rock.
Add marbles to fill the jar half full. The class may already have the concept of filling the pore spaces. Bring out the bottle of colored water and slowly pore it into the jar of marbles. Proceed with the analogy that the marbles are like the grains of sand in a sandstone and that crude oil is found within these pore spaces. This is a reservoir.