By Bob Feurer
A simple comparison of physical and chemical processes is possible for students during their study of weathering. Chalk, vinegar, water and test tubes, Petri dishes or aluminum dishes are usually readily available to most classrooms and are the materials needed for an activity on chemical and physical weathering.
To demonstrate some of the differences between chemical and physical weathering processes in rocks and minerals.
Chalkboard chalk (white or yellow as both will work), white vinegar, water, a hammer or mortar and pestle, and containers like test tubes, culture dishes, Petri dishes, small aluminum plates or other suitable containers, whatever is available.
- Assemble the materials as indicated by your teacher. Each student or student team will need about a piece and a half of chalk, three containers, a quantity of vinegar and water.
- Place approximately half of a piece of chalk in the first two containers. Cover the first container with vinegar and the second with water. Label the containers so you will be able to remember which is which at a later time.
- Check with your teacher about where to do the next portion of the procedure. You are to slightly crush the remaining half piece of chalk and place it in the third container.
- Now observe the three pieces of chalk. Create data collection table with enough space that will allow you to collect data for a couple of days as the water and vinegar evaporate. Note colors, smells, any changes in the chalk that may be visible at this time. Note also the contents of the dish itself. continue your observations until both the water and vinegar solutions have evaporates from the respective dishes.
- What changes, if any did you note during your observations about each piece of chalk? Discuss these in writing in a separate paragraph about each experimental set up.
- Based upon your observation and experience which of the experimental setups would indicate a chemical change, that some new material was created? What evidence exists for your conclusions?
- Speculate where in nature each of these processes might occur in a similar fashion.
- What effect might these processes play in the formation of soil?
- What do you think? Are these processes a good or bad thing? Why?
- Certain stone Egyptian artifacts have been moved from Egypt to this country. The artifacts that remain in Egypt are still in very good condition while those transferred to this country's east coast have suffered terrible damage due to erosional processes. What mechanism(s) do you believe might be the cause?