Obviously, boiling water isn't exactly like composting conditions or the slow, natural process of biodegradation. However, you can simulate (to some extent) the way certain materials break down compared to others when energy such as heat is applied to the system. This activity is great for teaching about recycling and composting.
Since two components of biodegradation are moisture and heat, we can attempt to simulate these conditions using boiling water for a simple activity you can do with kids to show them how easy or how difficult it is to degrade, or break down, certain substances. You can test any material you want. Good ideas of things to try are plastic, "compostable" plastic, cardboard, card stock, regular paper, food, aluminum foil, glue sticks, and more!
Step 1: Make the Object Clips
You want to make sure you have an easy way of getting the objects out of the water at the desired time points (explained in a later step) for weighing or tracing. So you want to take a binder clip and tie a string through the loops. The object will be clipped by the binder clip and lowered into the water.
Step 2: Check the Length of Your Strings
Make sure the clips lower all the way into the beaker with lots of overhang for the strings. These keeps little hands away from the heat source, a very important safety precaution!
Step 3: Choose Your Objects and Clip Them
In this picture I have chosen 4 objects to compare: a piece of recycled card stock, a piece of regular white copy paper, a piece of PLA corn plastic, and a banana chip. You may choose any objects you want to compare. Another thing worth doing which I did not do here is compare the PLA plastic to a piece of regular plastic, such as from a disposable "clam shell" to-go container.
The objects were cut into 1 inch squares so we can measure them against a grid and see how they change over time.
Step 4: (Optional) Get a Baseline Weight of Your Objects
You may want to make this experiment a little more interesting if you have access to a scale that goes out to two decimal places. You can get a baseline weight of all your objects, and weigh them at each time point to see how their weight changes over time spent in the boiling water.
Pro Tip: Get your objects wet first because they will be wet when you weigh them at the end and the water will significantly add to the weight.
Step 5: Get the Water Boiling, Then Add the Objects
If you have access to a lab, you can use the picture on the right with a real hot plate and borosilicate glass beaker. But if you're doing this at home, the picture on the left is a measuring cup (that looks like a beaker) from IKEA and a ceramic cook top stove. Any hot plate will do, as well, if it can get hot enough to keep the water boiling. A clear glass container is not required but it makes it easier to see what's going on.
Lower the objects into the boiling water and start the timer.
Step 6: Set Up and Fill in Your Data Sheet
Make a grid of 1 inch squares and laminate it. This will be your data sheet. This keeps it from getting wet, and you can then write on it with a dry erase marker and use it again and again! Take photos of it as you go, to log your results.
At each time point, record the size of the object by placing it on the grid and tracing around it. See in the example of what each object looked like at different time points.
Step 7: (Optional) Final Weight
Get a final weight on each object by unclipping it and putting it on the scale. You can do this at the beginning and at the end, or throughout the experiment for extra data points. Then you can plot it on a line graph for advanced classes, and see the trend for each object!
Step 8: Follow Up Questions
Ask the students:
- Are you surprised by the results? Why or why not?
- What do you think would happen if we boiled them for an hour? Two hours?
- How does boiling water simulate composting conditions?
- What is different about boiling water and compositing conditions? What factors are missing?
For even more follow-up questions, worksheets, our grow kit, and related activities, you can buy our lesson plan workbook and kit package that is aligned to the Next Generation Science Standards for 3rd to 5th grade and can be modified for multiple grade levels.
Visit www.growgreenspace.org/growkit for more information