Science teachers demonstrate the effects of chemical weathering on rock forms by placing samples of stones into different solutions. Provide three samples of five rock varieties, such as limestone and marble, for student observation. Place each rock in a clear plastic cup and label the type of stone. For the first sample of each stone type, add enough tap water to cover the rock. Prepare a solution of salt dissolved in water and submerge the second samples in the solution. Add carbonated water to the remaining cup. Allow rocks to sit overnight before observing and discussing the results of weathering with the class. Students will see some rocks show signs of disintegration while others appear unchanged. Rocks that contain calcium carbonate undergo chemical weathering when the carbon dioxide in the water reacts with the calcium and changes it to soluble bicarbonate, which breaks down the rock from the inside.
Use scissors to punch six small holes across the bottom of an 11-by-13-inch foil baking pan along one of the 11-inch sides. Line the bottom of the pan with soil from the yard. Place the hole-punched end into a second aluminum tray of the same size and prop the opposite 11-inch edge on two textbooks to create a slant. Fill a watering can and pour over the elevated side of the dirt-filled tray. Observe what happens. Discuss changes in the physical appearance of the soil and identify natural formations that are caused as a result of soil erosion over an extended period of time.
Deposition is, in some ways, the reverse of erosion. While shorelines are eroded as water carries away soil and stone, deposition leaves new sediment along boundaries of rivers and streams. High school students learn about environmental conditions and natural processes by measuring soil deposits using a deep bowl with a sieve or cloth filter inserted approximately halfway into the basin. Place the filter in a nearby stream or river at various points to compare soil deposition in areas of high and lower water velocity, as well as upstream and downstream from large rock formations. Determine which areas are likely to see less shore erosion based on test results. Students will observe that soil and sand continue to be swept along in faster-moving water, but settle in areas where the flow is slower. Rocks tend to trap sediment, so the shoreline upstream from stones will erode at a much more gradual rate than shores downstream.
Cut a steel wool pad in half and dampen one piece. Set each sample in a plastic freezer bag and label the bags "wet" and "dry." Seal the bags and leave them undisturbed for four days. Record observations of both steel wool samples before opening the bags. Remove the dry piece and attempt to pull it apart, then roll it between both hands over a paper plate. Repeat with the wet sample and compare the results. The chemical reaction between oxygen atoms in water and metal, called oxidation, will cause the damp wool to disintegrate so that it sheds large amounts of fibers onto the plate when the student rolls it and comes apart with less resistance than the dry pad.