Author: Beth Kennedy, Elaine Ulrich, Roberta Gangl, Susan Franz, Chris Bode, Kathie Owens
Source: Worms Eat My Garbage Website, Using Trash - How You Can Rethink, Reuse, Reduce, Recycle, and Rebuild, Scholastic Science Place
Students will bury organic and man-made materials, some of which are polymers, to see if they decompose. They will observe the materials and record their results. After seeing that the polymer of the six-pack rings does not disintegrate at all after being buried, they will learn that these can photo degrade. They will then design and perform an experiment to photo degrade the six-pack rings and record their results.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
Show the students the items that will be the objects of the investigation (pop bottle cut into pieces, steel can, piece of aluminum foil, a lettuce leaf, an apple core, a piece of bread crust, a piece of newspaper, a piece of plastic wrap or plastic sandwich bag, and six-pack rings). Ask students to describe the physical properties of each item. Make a record of students' descriptions (the before data) for comparison with the physical properties of these items after the experiment.
Ask students to predict what might happen to each item if it was buried for a day, a week, a year, or 100 years. Record students' predictions on the chart paper along with the physical descriptions.
Pose the question: What will happen to these items if they are buried for a period of time?
Have soil and bottles ready to distribute to each group.
Assessment: Monitor the students' answers to the questions and discussion. Before proceeding make sure that they have a descriptive knowledge of physical properties and decomposition. Make sure that they understand the problem to be tested.
Remind students of lab safety (handle materials properly, wear gloves when handling soil, keep soil out of your mouth and nose, wash hands thoroughly after finishing the activity).
Direct students to bury each of the items in the soil. Water the soil until damp.
Water the soil for three days. After at least three days (you can certainly wait longer if you have the time), dig the items up and see what has decomposed and how much. Have students list the physical properties of these items.
Assessment: Monitor the work of the students. Are they carrying out the procedures safely, and discussing possible findings in their group?
Have students report their findings. Encourage class discussion to compare the before and after list of properties. Which of the items changed or did not change? Did some items change faster than others? Which ones? Did the students' findings agree with their predictions?
Discuss with the students that some materials buried in the soil enrich it while others ruin the soil and make it unfit for farming. Discuss reusing items rather than throwing them away.
Assessment: Ask the students to draw a picture of items that would disappear completely into the soil if they were given enough time. Draw another picture showing items that we throw away that do not decompose into the soil.
Help students design experiments to find out how long it takes for light to degrade six-pack rings. The rings can be put into plastic bags and hung in a window, outside on walls, set on window ledges or other sunny places. Another option would be to use a UV grow light to hasten the photo decaying process. Otherwise, it should take about three months for them to decay. Students can discuss the benefits and disadvantages of such a long decay time.
Also discuss with students recycling of waste materials. Show examples of materials that can be recycled. Show examples of items made with recycled materials.
Assessment: Help the students write letters to their parents encouraging them to buy products that can be recycled or products made from recycled materials.
Be aware that K-2 students may have no idea what happens to items when they are buried. Some may think that items do not change at all; others may think that decomposition occurs quickly and that every trace of the item has disappeared.
About 20% of the garbage that ends up in a landfill is organic matter that decays or rots. The decay is brought about by bacteria, earthworms, and fungi. Items that do not decay stay virtually untouched for thousands of years or longer. Most plastic items do not decay. In the presence of sunlight some polymeric materials degrade.
Much of our garbage could be recycled and, therefore, save valuable space in the landfill for items that cannot be recycled. Examples of materials that can be recycled include: paper, glass, aluminum, and motor oil.
Investigate the recycling facilities in your community and share information about these places with your students.
Wash hands after burying the items.
Students will be able to practice recycling, reducing and reusing.
Have ready for inspection additional items similar to the ones used in this experiment and ask the students to predict the fate of these items if they were buried in a similar way and for the same length of time as the ones in the experiment. Using their findings from the experiment, have students tell you why they predicted as they did.
Pacing/Suggested Time: Two science periods.; Decomposition will take anywhere from 3 days to as long as you desire.