Chemical Reactions: What is Plastic Made From?
2 days (drying time for casein plastic)
Area of Science
Chemical reaction, polymerization, plastic, properties of matter
Svenja Lohner, PhD, Science Buddies
Video narration by Jennifer E Paz
Free for a limited time thanks to individual donors
Chemical reactions can result in interesting products! In this lesson, students learn how plastics are made by conducting a polymerization reaction in a simple milk-to-plastic transforming experiment. During their experiments, students will be able to compare the physical properties of their reactants (milk and vinegar) and their resulting organic casein polymer.
- Explain what plastic (a synthetic polymer), is made of on a molecular scale.
- Describe how a chemical reaction, like polymerization, can change the properties of a substance.
- Reflect on the consequences of using natural resources for industrial purposes.
For teacher preparations:
- Milk (enough for each group of students to have 1 cup; about 1 gallon for 15 student groups)
- Stove and pot (1) or microwave and microwaveable container (1) to heat up the milk
- Thermos or insulated container big enough to hold all the hot milk
- White vinegar (enough for each group of students to have about 4-5 tsp.; about 2 cups for 15 student groups)
- Measuring cup
- Optional: food coloring, small cookie cutters, and/or markers
- Styrofoam® or another heat-resistant cup (12 oz. or bigger)
- Mini cup with lid (2 oz.)
- Paper towels (6)
- Spoon (1)
- Student worksheet
- Print out a worksheet for each student.
- Heat all the milk you need for your class (1 cup per student group) in a pan on a stovetop or burner until the milk is steaming. Alternatively, you can microwave the milk in a microwaveable container by warming it at 50% power (two minutes at a time) and watching it to make sure it does not overflow. The milk will be steaming when it is sufficiently hot.
- Store the steaming hot milk in a thermos until it is needed. It should stay warm enough for at least two hours.
- Prepare a materials station for students. Place the measuring cup, the thermos with the hot milk, and a bottle of distilled vinegar at the station so that students can measure out these materials during class. Optional: if you decide to use decorative materials such as small cookie cutters, food coloring, and/or markers, place these at the materials station as well.
- For the explore part of the lesson, provide the students with a work surface that can get damp.
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