Begin by placing some soil in one of the cookie sheets. Pack down generously.
In the other cookie sheet, add some sod to half and some soil to the other half, packing down generously.
Poke several holes in the bottom of the gallon jug.
Make an incline with some wood blocks, books, etc and place the cookie sheets on them at an angel. Place them in the 9x13 pans. Secure with a push pin if needed to prevent them from sliding.
Loosen the lid on the gallon jug a bit and let it "rain" on the cookie sheet with only dirt. Notice how the soil moves with the water and how much sediment is collected at the bottom of the 9x13 pan.
Next, let it "rain" on the cookie sheet with the grass strip (make sure the grass strip is at the bottom of the pan).
Notice how the grass filters out much of the sediment and how much clearer the water is that has collected in the 9x13 pan.
Optional: dump water from the 9x13 pans and observe how much sediment is in each one. (the one with only the soil will have less)