Click here to print this page.

Akron Global Polymer Academy Lesson Plans

Young's Modulus: An Investigation of Stress Versus Strain Using PDMS Polymer

Grades: Grades 11-12
Author: Jesse Groff
Source: This material is based upon work supported by the National Science Foundation under Grant No. EEC-1161732.


This Lesson is based upon Young's Elastic Modulus. Young's Elastic Modulus (E) closely relates itself to the spring constant (K) used in traditional classroom physics when teaching Hooke's Law. This is outlined in detail in the power point for further information. Through this construction, this lesson can bridge the gap between the engineering scope and traditional physics concepts taught in the classroom. By using a silicone base polymer, we will investigate young's elastic modulus by changing the chemical composition. This polymer used comes from the Sylgard company. This comes as a mix and pour kit of silicone polymer with a cross linking agent (Sylgard 184).

By creating different weight percent solutions students can vary dimensions and physical properties easily. By mixing the two ingredients, a silicone polymer base and a curing agent, and based on the ratio of the two ingredients; changes in shape/length can be identified and measured based on an applied external force. Also by increasing the thickness of the sample itself, the change in the cross sectional area, can cause changes in shape and length when an applied external force is applied. Students will apply this external force by hanging masses from binder-clips that are attached to the created samples and measuring length changes in the sample. This lesson does not require high tech material and only the silicone polymer would have to be ordered by an outside source, available on the internet.

***Secondary Option: The same principal can be applied to rubber bands so cost can be kept minimal while still investigating the same concept. To facilitate this, different grades of rubber bands can be purchased from a store; this would change the modulus of the material. Secondly, one could keep the same grade of rubber bands and vary the thickness, thereby affecting the cross sectional area.


What should students know as a result of this lesson?

What should the students be able to do as a result of this lesson?


***SAMPLES: This lesson is to have SIX samples for each group. Students will be able to choose from the following variables to research: Sample Thickness (cross link ratio constant 20:1). Sample Cross-link Ratio ( Thickness held constant 5mm).



Day 1:

Students will be given a choice of a variable to study:

**Direct Instruction Lecture Power-point with guiding questions attached.

**Demonstration worksheet attached with slide timeline.

Day 3:


Day 1:

Day 2:

Day 3:

Day 4:


Day 1:

Day 2:

Day 3:

Day 4:


Day 3:


Day 4:

As individuals, have students complete a lab reflection packet including


Students must know the following in order to actively participate in this lesson:

  1. A good understanding of the metric system and how to convert between units.
  2. An understanding of the scientific method as it pertains to engineering.
  3. What a polymer is and how PDMS is one of those polymers.
  4. An understanding of cross-linking between molecules, and what cross-linking does.
  5. An understanding and how to find/define cross sectional area.
  6. An understanding on how to define/calculate stress and strain, in script and mathematically.
  7. An understanding on how to calculate density.

Best Teaching Practices

Alignment with Standards

NGSS Standards:

Common Core Standards:

Ohio Standards:

Content Knowledge


Safety Equipment Needed:

Safety Procedures Reminder:


This content is applied to the real world by relating the lesson to testing materials for engineering purposes. Engineering seeks to find uses for inventions and innovations that can make life be easier and have better quality. Materials must be tested and scrutinized before consumers can have a chance to buy and use the new technology. This testing is a skill that must be learned and developed and this lesson gives a window into that process. Students who go on into the engineering field need to be able to do this process of testing and analyzing in order to meet a certain goal.



Other Considerations

Grouping Suggestions: I have about 25-30 students. I am grouping my students in groups of 5. I think that five is a good number for this lab because materials are costly and there is going to be a high number of samples. In order for this lesson to go smoothly I think larger groups are better than groups of two or three unless you are working in a system that has small class sizes, then groups of two or three would be ideal. It basically comes down to amount of samples and cost for materials.

Pacing/Suggested Time: My classes are 47minutes in length. I will spread this lesson out over four days.

DAY 1: Lecture with quick demos to build pre-requisite knowledge, choosing a variable to study, (thickness/cross-link ratio). Engagement/Exploration/Explanation

DAY 2: Reminder of class goal timeline, Creating of samples, develop a plan for testing their samples, Exploration/ Explanation.

DAY 3: Reminder of class goal timeline, Finish plan for sample testing, test half their samples, discuss problems, guide groups to help properly test remaining samples, Collect data. Engagement /Exploration /Explanation /Elaboration.

DAY 4: Analyze data, prepare simple graphs on boards, present findings to the class, and discuss findings, Exploration /Explanation /Elaboration / Evaluation.

Printable PDF Worksheets