Investigating Polymers: Comparing Two Liquid Glue Based Polymers

This activity is designed for students to conduct a controlled experiment and to enhance their skills in observation and the recording of their observations.
Key concepts:
The students will understand that a polymer is a long chain of molecules.
The students will give examples of physical properties.
The students will make observations of the properties of the two polymers.
Vocabulary: polymer, molecule, variables, physical properties, elasticity

This activity is designed to be part of the study of matter and may be used after students have been introduced to properties of matter and molecules, or as part of a lesson on polymers. The experiment may be conducted in pairs or small groups in a lab or classroom setting and will take approximately 40 minutes. Grades 3-6.

You will need the following materials:
Elmer's or other liquid white glue
Borax
Liquid laundry starch
Water
Paper towels
Small plastic cups (4 per group)
Straws or craft sticks for stirring (2 per group)
Measuring spoons

Before beginning the experiment, review properties of matter. Students should have a basic understanding of molecules and polymers.

Polymer One (glue and liquid laundry starch)
1. Pour 1 teaspoon of glue into one cup. Pour approximately 3 tablespoons of liquid laundry starch into another cup. Students should record their observations of the two liquids in their science notebooks.
2. While stirring with the craft stick, slowly add the liquid laundry starch to the glue until it forms a glob.
3. Remove the glob and knead it. Excess starch may be patted off with a paper towel.
4. Students should stretch and manipulate the polymer, then record their observations in their science notebooks noting how the properties have changed.

Polymer Two (glue and Borax solution)
1. Create a saturated Borax solution in one cup by mixing 2 teaspoons of water and ¼ teaspoon Borax. Stir until as much Borax dissolves as possible.
2. Place 1 teaspoon of glue in another cup (some directions call for 1 teaspoon of water to be added also). Students should record their observations of the two liquids in their science notebooks.
3. While stirring with a craft stick, slowly add Borax solution until a thick glob forms. This will take just a small amount of solution.
4. Remove the glob from the cup and knead it. Excess solution may be removed with a paper towel.
5. Students should stretch and manipulate the polymer, then record their observations in their science notebooks, noting how the properties have changed.
6. Compare the two polymers. How are they alike or different?

When all of the students have finished the experiment, discuss their observations as a class.

Students should wear safety goggles during this experiment.
Be careful not to get it on clothing or carpet.

If time is limited, the cups of Borax solution and liquid laundry starch could be prepared ahead of time by the teacher. You may want to double the amounts of glue and solutions used in the experiment to provide a larger sample for students to work with.

Polymer One has the consistency of Silly Putty and the students love to play with it. I have often had students make a lump of their own putty. Each student is given about 20ml of liquid laundry starch in a cup and adds glue until a glob of putty forms. I have found that the measurements don't need to be exact. If someone adds too much glue, we just add a little more starch. We sometimes remove the excess starch from the putty by rinsing under cold water, but be sure none of the polymer goes down the drain. It may be colored using markers. Using the blue gel school glue creates a more rubbery polymer. Putty should be stored in an airtight container or bag. I always forewarn my students that it is quite possible someone's putty won't form and will remain a gluey mass, even though everything was done according to instructions.

I have not tried this activity in this format but feel confident of its success. The experiment is more controlled, and comparing the two polymers will provide a more comprehensive experience for the students.

Assessment will be based on observation of student participation in the experiment and thoroughness of written responses in their science notebooks.

5.I.A.1.2- clear communication of findings
5.I.B.1.1- perform a controlled experiment

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