Here are several investigation topics tailored for a fifth-grade level:

1. The "Decomposition Timeline" Simulation

Students often hear that plastic lasts "forever," but seeing the contrast is more impactful.

• The Investigation: Bury a plastic bag, an apple core, and a piece of paper in a container of moist soil.

• The Goal: Dig them up every two weeks to observe and document the physical changes. Use a "Degradation Scale" (1–10) to track which items are breaking down.

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2. The "Laundry Lint" Microplastic Hunt

Most people don't realize their clothes are a source of plastic pollution.

• The Investigation: Collect the lint from a dryer trap after a load of synthetic clothes (fleece, polyester) versus a load of 100% cotton.

• The Goal: Use a magnifying glass or a basic microscope to look for tiny plastic fibers. Students can hypothesize why synthetic fabrics shed more and how those fibers might end up in the ocean.

3. School Cafeteria "Trash Audit"

This turns the school into a living laboratory for data and statistics.

• The Investigation: With gloves and adult supervision, categorize the plastic waste from one lunch period (e.g., milk cartons, straw wrappers, chip bags).

• The Goal: Use the data to create bar graphs showing the most common types of plastic. Calculate how much of that waste could be eliminated if every student used a reusable water bottle for one week.

4. The "Packaging Engineering" Challenge

This moves from identifying the problem to solving it.

• The Investigation: Examine common grocery items (like a box of crackers) and map out every layer of plastic packaging involved.

• The Goal: Design a "Prototype" for a new way to package that same item using only compostable or reusable materials. Students can present their "Blueprints" to the class.

5. Water Filter Experiment: Can We Catch Microplastics?

A hands-on look at how difficult it is to clean up plastic once it's in the water.

• The Investigation: Create a "contaminated" water sample using glitter (which represents microplastics) and dirt. Build a tiered filter using sand, gravel, and coffee filters.

• The Goal: Measure how much "plastic" (glitter) makes it through the filter. This illustrates why preventing plastic from entering the water is easier than removing it later.