The best examples of chemical weathering are monuments in cities and historic sites. Try to differentiate among the change in appearance only, and change in composition. The students should have discussed these types of changes. It is a difficult concept to some and may take ten minutes to review. Ask the students if chemical weathering would occur in a damp environment or in a dry one.
Mechanical erosion can occur in dry and damp environments.
The students' workbooks do not have the pictures of erosion that are in the teacher guide. These pictures of different agents of erosion on different landscapes are accessible from the Education page on the park's website. These pictures can be printed to pass out to the students to show various examples of erosion. If you have ensured that the students understand this topic, group the students into 4-5 members and supply them with two pictures. Have the students decide if erosion has occurred in each picture and what type of erosion.