Read the following activity and answer the following questions:
 
The students perform the following observations:

1. Light the candle and observe the melting wax and the burning flame.
2. Observe the rusted iron nail.
3. Examine the small stone and discuss how rocks become soil over many years.
4. Observe the potted plant and discuss how its roots may slowly crack rocks.
5. Sprinkle a little water over the soil and discuss how flowing water may carry away soil during heavy rainfall.

The students then record their observations and answer the following questions.
 
1. During the activity, which observation represents a slow natural change?
 
2. Which process observed in the candle activity is a physical change?
 
3. Why does planting more trees help reduce soil erosion?
 
4. Which conclusion can be drawn after completing this activity?