- Large bucket or tank full of water. A clear tank or aquarium is ideal.
- Disposable plastic bottle with lid
Either demonstrate while taking suggestions from the class, or have sets of materials that groups or individuals
can investigate on their own. This activity can be done with minimal instruction if students are used to
What are the properties of a plastic bottle as it interacts with water? Does it sink or float? Can it also do
the opposite? Students will discover that the plastic bottle sinks and the plastic lid floats. (This is usually
true, but check your chosen materials.) Most plastic consumer items have a "chasing arrow" symbol containing a
number. Some people think this means the item is recyclable, but it actually tells you what kind of plastic it's made from. Most water and soda bottles are #1 (PET, polyethylene
terephthalate) or #2 (HDPE, high density polyethylene). These plastics sink in water (although students may
discover that they can make the bottle float). Lids are often #5 (PP, polypropylene), which floats in
water. What are the implications of these properties? What animals might come into contact with these different
types of plastics? Two examples are albatross (ocean birds that collect their food from near the surface) and
gray whales which feed by stirring up the sediment on the sea floor. In fact, bottle caps
are commonly found in the digestive systems of Laysan albatross on Midway Island. Can your students come up
with conditions that would cause a polypropylene item to sink?
After this investigation you may follow up with the activity You Are What You Eat from Waves, Wetlands, and Watersheds
and direct students to the webpage The Problem with Marine Debris.
You can download a slideshow from Gilroy
High School teacher Jeff Manker, reflecting on his experience visiting Midway
Island, showing the impact of plastic pollution on the Laysan albatross that nest there, and how choices that
students make on the mainland can help address the problem.
Provides Support for NGSS Performance Expectations:
- MS-ESS3-3. Apply scientific principles to design a method for monitoring
and minimizing a human impact on the environment.
- MS-ESS3-4. Construct an argument supported by evidence for how increases in
human population and per-capita consumption of natural resources impact Earth's systems.
- MS-LS2-4. Construct an argument supported by empirical evidence that changes
to physical or biological components of an ecosystem affect populations.
- HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of
human activities on the environment and biodiversity.
- HS-ETS1-1. Analyze a major global challenge to specify qualitative criteria
and constraints for solutions that account for societal needs and wants.