Description
Give your students a fun, hands-on experience in protein denaturation with this easy milk plastic activity. By adding heat and acid, students turn whole milk into biodegradable milk plastic!
To get the most out of doing this lab, your students will want to have a basic understanding of proteins. Check out this resource! It is one of my favorite hands-on activities that really gives kids a solid understanding of how proteins fold, and denature!
If they do not know why proteins denature in acid, that is okay! This activity can be used as a starting point for research or class discussion.
Materials for the Milk Plastic Activity
- Milk (whole is best but 2% works)
- Vinegar
- Heat source (hot plate, microwave)
- Cheesecloth or strainer
- Food coloring
Denaturing Milk Proteins
When heat and acid are applied to milk, the casein proteins denature and separate from the whey. The long polymer strands of denatured protein are malleable, and can be colored and molded into fun shapes.
One cup of milk yields about 1/3 cup of milk plastic. I allow my students to work in pairs. At the end they divide the milk plastic into two balls so that each can choose their own color and shape.
Students can knead food coloring (and glitter!) into the curds and mold it into whatever shape they want! I like to do this experiment close to Christmas and use the milk plastic to make ornaments for our classroom Christmas tree!
This Free Resource Includes:
- Lab instruction sheet
- Student question sheet
- Key for question sheet
- Detailed teaching guide
Biodegradable Plastic
This project gives you a chance to discuss sustainability and the issues with typical plastic waste. What kinds of applications are there for biodegradable plastics like milk plastic? What are the limitations?
After a few weeks in the classroom (after Christmas break) I allow students to take home their creations, or donate them to science! We place the donated milk plastic shapes outside in various conditions to observe how biodegradable they really are.
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*** Stay Curious! ***
