Summary

In this lab, students will try to separate plastic spoons that have been attached together with different adhesive materials using a variety of solvents.

Grade Level

Middle school

NGSS Alignment

This lab will help prepare your students to meet the performance expectations in the following standards:

• MS-ETS1-2: Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem.
• MS-ETS1-3: Analyze data from tests to determine similarities and difference among several design solutions to identify the best characteristics of each that can be combined into a new solution to better meet the criteria for success.
• Scientific and Engineering Practices:
  • Asking Questions and Defining Problems
  • Planning and Carrying Out Investigations
  • Constructing Explanations and Designing Solutions

Objectives

By the end of this lab, students should be able to

• better explain the concepts of solvents and solutes.
• distinguish between adhesive bonding and chemical bonding.
• remove adhesives from a variety of surfaces.
• describe and differentiate between the chemical and physical changes taking place.

Chemistry Topics

• Solvents
• Solubility
• Physical Change
• Chemical Change

Time

Teacher Preparation: 60 minutes

Lesson: 40 minutes plus discussion afterwards

Materials

Each station will need:

• 4 sets of two clear polystyrene plastic spoons that have been glued together with Super Glue^®.
  • The teacher should prepare these in advance by putting one drop of Super Glue^® between two spoons and letting set for 1 minute.
• 4 sets of two white polystyrene plastic spoons that have been previously glued together with epoxy.
  • The teacher should prepare these in advance by putting a small amount of epoxy between two spoons and letting it set overnight.
• 4 sets of two black polystyrene plastic spoons that have been previously melted together with a flame (this will be the control sample).
  • The teacher should prepare these in advance by heating lightly on the edges of the two spoons with a lighter or Bunsen burner until they have welded together. This takes some practice.
• Four 50ml beakers
• Acetone (nail polish remover)
• Water
• Soapy water
• Rubbing alcohol
• Lab trays or Rubbermaid^® tubs to catch the mess (there will be a mess)

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• Clean up materials and dispose of chemicals as directed.
• Make sure you are working in a well-ventilated area; avoid inhaling the acetone and rubbing alcohol.
• Keep acetone and rubbing alcohol away from heat sources and direct sunlight.
• Replace lids on containers for both acetone and rubbing alcohol when they are not in use to minimize vapors and odor.

Teacher Notes

• Students should have already learned about and discussed chemical and physical changes as well as solubility and solvents.
• You should have separate containers ready to dispose of the used plastics spoons and the used chemicals.
• There will be a stink. If students are irritated or do not like the smell, they can go into the hall/leave the room. Open windows, and ventilate the area properly: turn on exhaust fans during the lab.
• We are looking for discovery and discussion in this inquiry lab. They should discover that the spoons themselves are dissolving in the solvent. This is an interesting discussion.
• The students should note that the acetone will easily break down the Super Glue, but it doesn't work quickly on the epoxy or welded control. They should also note the spoons themselves will begin to get very flexible and 'dissolve' as the polystyrene is soluble in acetone. This should lead to a further discussion on adhesives, how plastics are made, and consideration of how they are bonded together.
• I tell my students this is a challenge; I have ice cream, but they must separate the spoons so that they have something to eat it with. No spoon, no ice cream. At the end of the lab we eat ice cream (with new spoons) outside of the lab setting.