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LAB in Chemical Change, Exothermic & Endothermic, Kitchen Chemistry, Kitchen Chemistry - High School. Last updated October 15, 2020.

Summary

In this lab, students make homemade glue from milk and compare it to commercial glue.

Grade Level

High School

NGSS Alignment

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

  • HS-PS2-6: Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials. 
  • MS-PS1-2: Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred. 
  • Scientific and Engineering Practices:
    • Analyzing and Interpreting Data

Objectives

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

  • Convert measurements, given necessary equivalent factors.
  • Describe the meaning of coagulate.
  • Identify indicators of a chemical change.
  • Determine if a reaction is exothermic or endothermic.
  • Comparatively test the strength of glue created from a reaction with commercial glue.

Chemistry Topics

This lab supports students’ understanding of

  • Chemical Reactions
  • Chemical Change
  • Endothermic & Exothermic
  • Separating Mixtures

Time

Teacher Preparation: 10 minutes

Lesson: 45 minutes

Materials

  • Small sauce pan
  • Skim milk
  • Heat source
  • 25 mL vinegar
  • Coffee filter (or equivalent)
  • 1 g baking soda (1/2 tsp)
  • Stirring utensil
  • 25 mL water
  • Measuring cup

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.
  • Do not consume lab solutions, even if they’re otherwise edible products.

Teacher Notes

  • I use this lab experiment as a take home lab assignment. Find out more about my take home labs in the March issue of Chemistry Solutions or in the AACT Webinar archive.
  • The materials are commonly found at home, so have students to check for availability. If this is difficult, allowing students to complete the lab in the classroom before or after school is a good option.
  • This particular lab is designed as an extra credit opportunity. I offer Extra credit labs as optional and proactive— i.e., they are due before the test to which they will be credited.
  • In a lab like this, we use it as an opportunity to emphasize new terminology (such as coagulation) that isn’t traditionally required by the state and try to add a review of some required concept (like neutralization) as a part of the questions that accompany the lab.

For the Student

Background

Little Miss Muffet
Sat on a tuffet,
Eating of curds and whey;
Along came a spider,
And sat down beside her,
And frightened Miss Muffet away.

Purpose

You will make glue from milk and compare your glue with commercial glue.

Discussion

White glue is often made from the protein in milk called casein. The casein is separated from the milk by the processes called coagulation and precipitation. At a glue factory, the casein is dried and ground up before it is made into glue. Casein is also used in some paints and to make a type of plastic-like button.

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.
  • Do not consume lab solutions, even if they’re otherwise edible products.

Materials

  • Small sauce pan
  • Skim milk
  • Heat source
  • 25 mL vinegar
  • Coffee filter (or equivalent)
  • 1 g baking soda (1/2 tsp)
  • Stirring utensil
  • 25 mL water
  • Measuring cup

Helpful Equivalents

  • 1 tablespoon = 0.5 oz. = 15 mL
  • 3 teaspoons = 1 tablespoon
  • 1 cup = 250 mL (approximately)

Procedure

  1. Pour 125 mL of skim milk into your sauce pan.
  2. Add 25 mL of acetic acid (vinegar).
  3. Gently heat the milk, stirring continually, until small lumps form.
  4. Remove the pan from the heat and continue to stir until no more lumps form.
  5. Allow the lumps (curds) to settle.
  6. Filter the curds from the liquid (whey) by using the coffee filter.
  7. Gently press the filter paper around the curds to squeeze out the excess liquid.
  8. Pour out the whey and return the solids to the pan.
  9. Add 25 mL of water and stir to rinse.
  10. Add about ½ tsp. baking soda (NaHCO3). Stir and watch for any bubbles to appear.
  11. Filter again and congratulations, you have made glue!
  12. Test the adhesive properties of your product by make an “arts and crafts” item.
  13. Compare it with the adhesive properties of commercial glue. Bring your project to class.

Reactions

Coagulating the protein and neutralizing the vinegar are chemical changes. The coagulated protein, casein, is produced by adding acetic acid and gentle heat. The solid casein is the precipitate. The reaction of the baking soda and vinegar is as follows:

NaHCO3 + HC2H3O2 → NaC2H3O2 + H2O + CO2

Analysis Questions

  1. What is the meaning of the word “coagulate?”
  2. Is this reaction endothermic or exothermic? Justify your answer.
  3. What are curds and whey? (Rhetorical addendum: Why was Miss Muffet eating them?)
  4. What is the purpose of the baking soda?
  5. Would the reaction have worked if the baking soda was added at the beginning? Justify.
  6. How did your glue compare to the commercial glue?
  7. Have a parent sign your work.