Demonstrate chemical weathering: drop vinegar (acid) onto limestone or chalk and watch it fizz — the acid is reacting with and dissolving the rock, just as acid rain slowly wears away limestone. Recap biological weathering (tree roots, mining) from Lesson 9.
Then introduce the three-step movement of material with the slide deck's animated flow: erosion (pieces picked up), transportation (carried along) and deposition (dropped somewhere new). Model the tray set-up: sand and dyed salt, moved with water (a watering can) and wind (a straw).
Groups run the erosion model: build a small slope of sand with dyed salt, then use water and wind to erode, transport and deposit it, observing where the material ends up. Discuss with guiding questions: What moved the material? Where did it settle? What would happen to a farm's topsoil in a big storm? How could we slow it down?
Students complete the Wearing Away worksheet: ordering and describing the three steps, describing their tray-model observations, explaining the weathering/erosion difference, explaining why topsoil erosion threatens food, and suggesting a way to slow erosion.
Exit ticket: give one example each of weathering and erosion and explain the difference.