Physical and Chemical Weathering in the Wildlands

Grade Levels: 3rd - 12th. (Note: This experiment can be simplified or made more challenging depending on the developmental levels of your students. See Teacher Information.)

Approximate Time Involved: Over a period of three weeks, there will be one 30 minute session every Friday to examine and discuss results.

National Science Standards Addressed:

Content Standard A: As a result of activities in grades K-12, all students should develop

Abilities necessary to do scientific inquiry
Understanding about scientific inquiry

Program Standard D: The K-12 science program must give students access to appropriate and sufficient resources, including quality teachers, time, materials, and equipment, adequate and safe space, and the community.

Good science programs require access to the world beyond the classroom.

Teacher Information:

Different objects are affected by weather in different ways. Your students will be observing the physical and chemical changes that occur due to weathering. This experiment will be done in two parts. For part I your students will be comparing different kinds of materials, and for part II they will be comparing different types of metal. This experiment will be held in the Wildlands. Be sure to place the hanging items/materials up high enough to not be disturbed by the other school children or neighboring children. If you have a digital camera in the classroom, you may want to photograph the items being observed each week so that the students can look back at what changes occurred.

This should become a team exercise where your student groups might each develop and write a hypothesis, list the materials they would use (cloth, plastic, leather, cardboard, paper, wire or rope, clothes pins or paper clips), the number of each item, and a procedure. An excellent way to assess this activity is to have the teams repeat each other's experiment to see if they achieve the same results. This will also replicate the real world challenges facing a research scientist.

When the students are ready to develop their own extensions, they could see which side of the school protects the items the most, or spray the items with water repellent, etc.

Challenging Your Students to Be Problem Solvers:

Which substance-plastic, paper, cardboard, material from cloth, leather-will change the most due to physical or chemical weathering when left on the playground for three weeks?

Needed Materials:

Part I: 8 ½" x 11" sheets of material (plastic, paper, cardboard, cloth and leather), wire or rope, and clothespins or paper clips. HINT: Use bright colorful materials!

Part II: Same as in part I, but materials hung on the rope should be different sheets of metal. (copper, aluminum, and brass are easily obtained in large craft stores.)

Safety Rules: Do not allow your students to climb or stand on chairs to reach the hanging wire or rope. If hanging out a second story window, do not allow your students to lean out the window. Tape any sharp metal edges. Avoid falls as much as possible!

Procedure :

Separate your students into five groups. Each group will be responsible for recording one of the materials

Student Information: You are to observe the physical and chemical changes due to weathering. For part I of this activity you will be looking at physical changes in the materials listed for part I. Different metals will be observed for chemical changes in part II. For each part you will need to have a control group that should be hung indoors. You will observe the changes each week for three weeks. To record these changes you will need to prepare a plastic grid ahead of time. This is done by making a copy of graph paper (cm squares) on overhead plastic sheets. If your teacher is able to provide a digital camera, you may want photograph the items each week so that you can look back at the changes that occurred.

Procedural Steps for Conducting the Investigation

Part I: Physical Weathering

1. Draw a fold line 1" from the top of each item so the items are folded consistently.

2. Stretch a rope/wire high above the heads of students somewhere outside near your classroom.

3. Using clothespins or metal paper clips secure the items to the rope or wire.

4. A control set should be hung indoors in the same manner.

5. After one week take the items down to record any physical changes that have occurred. To determine physical changes, you will have prepared a plastic grid to place over the items. This is done by making a copy of graph paper (cm squares) on overhead plastic sheets.

6. Place grid over one of the exposed items and using a light color marker color the squares where there seems to be a change (different color, tear, rust, etc.).

7. Count the colored squares for each item, record in a chart, and make a graph.

8. Repeat steps 6 and 7 for each item.

9. Return the items to the rope/wire to hang in the same manner as before.

10. Repeat steps 5 - 9 for the control set.

11. Repeat steps 5 - 10 for two more weeks (skip step 9 on the last week) so that you have three weeks worth of data.

Part II: Chemical Weathering

1. Repeat the steps above but hang different sheets of metal on the rope. Still include a control set indoors.
2. You will color the squares in the grid that cover a chemical change in the metal. (Ex. rusting or corrosion)

Below is a list of questions that can be used to stimulate student discussions. If your students are at a developmental level where you are able to challenge their higher level thinking skills, then only present them with the first set of questions from each group below. Use the second list of questions as a way to stimulate thinking when you students seem unable to expand their knowledge on their own.

Examining Results

Discussion Questions that Require More Critical Thinking Skills:

What were your conclusions for this experiment?
What could you infer based on your conclusions?
How would you design this experiment differently the next time?

Discussion Questions that Require Less Critical Thinking Skills

What types of changes did you find on the items?
Did using rope or wire increase the number of changes on the items?
If the answer to the above question is "yes", did the rope or wire help develop more changes?
Did the outside temperature have any impact on the changes of the items?
Would you expect to find the same changes of each item? How could you test your predictions experimentally?

Physical Change Links

Exploring Science.Com Highly interactive science activities for students and educators.

Chemistry Weekly chemistry articles and chemistry Web links for students and teachers

Sub-Tropical Testing Service See how they test products to see how well they last out in the elements.

Effects of Physical Changes on Objects Here is another activity you can try with your students.

Weather.com Check the forecast for the week.