When we study ecosystems, we sometimes forget about the first metre of soil that supports just about everything above it as well as the rich life that is in the soil. Animal decomposers such as worms, beetles, and other insects as well as microbial life such as bacteria and fungi are busy at life. Such wonder under our feet!
Soils for different ecosystems provide the abiotic component of the system. Soils are generally heterogeneous mixtures that can be separated physically by using water and heat. There are numerous opportunities to demonstrate particle theory within these mixtures/separations and it makes a very nice way to explicitly link several strands together! Students should have prior knowledge that solubility is a property of substances, that the amount of solubility varies between substances, and that salt readily dissolves in water.