Hardware cloth and two glass jars are all you need for this demonstration.
Cut the hardware cloth so that it will support a soil clod at the top of a jar filled with water.
Choose two soils which you suspect will have different organic matter contents (garden versus lawn, no-till crop field versus conventional tilled crop field). Observe the different stability of the soil material.
A soil clod high in organic matter will stick together. The water will be clearer (left). A soil clod low in organic matter will slake rapidly. The water will soon be cloudy (right).