• Strategy: Supporting Youth Development Through STEM
  • Skill: Connecting to Prior Knowledge & Experiences
  • Time: 60 Minutes

Plastics Density

Learn about recycling and investigate the different properties of plastics, how numbers on plastic are related to their properties and how they are recycled.

In this activity, youth will investigate how different numbered plastic have different properties.


Learning Objectives:

  • Youth will be able to describe how the properties of different plastics affects their density.
  • Youth will be able to identify the benefits of recycling plastics.



  • Examples of plastic number 1-7
    1. Plastic drink bottle with cap and plastic non-bottle;
    2. Plastic bottle with cap  and plastic bag;
    3. PVC pipe and container;
    4. 6-pack ring and plastic bag;
    5. Plastic container;
    6. Expanded Styrofoam coffee cup;
    7. Non-expanded plastic picnic-style disposable cup;
    8. PLA bio-based plastic; paper cup
  • Tubs of water for each youth group. Plastic storage bins work well.
  • Aluminum Foil
  • Salt
  • Hot tap water
  • 3 thermometers
  • Optional – pieces of fabric (fur, flannel, silk, cotton, synthetic fabrics)
  • Copies of worksheet and plastic types sheet for each youth.