Bridging to Polymers

Contributor
Teach Engineering from the National Science Foundation
Type Category
Instructional Materials
Types
Instructor Guide/Manual , Experiment/Lab Activity
Note
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be “fully aligned,” the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.

Reviews

Description

This review focuses on the lab activity identified in a series of lessons that explore the basic characteristics of polymers through the introduction of two polymer categories: thermoplastics and thermosets. In the lab activity, students act as engineers to create a thermoset material from a epoxy-amine mixture and then mechanically test them by applying different stresses. Each student group makes a unique polymer using a different ratio of epoxy and hardener so that class data can then be used to optimize the ratio to fabricate the thermoset to the desired conditions. The full lesson sequence begins with teacher demos in which students observe the unique behaviors of thermoplastics and discuss the fundamentals of thermoset polymers are discussed, preparing them to conduct the associated activity in which they create their own thermoset materials and mechanically test them. The introductory demonstration and discussion activities for the lesson, “Close Encounters of the Polymer Kind,” are available here: https://www.teachengineering.org/view_lesson.php?url=collection/uoh_/lessons/uoh_polymer/uoh_polymer_lesson01.xml These intro lessons are very teacher-directed. If used, the teacher should consider how to adapt them to better engage students in the learning.

Intended Audience

Educator
Educational Level
  • Grade 12
  • Grade 11
  • Grade 10
  • Grade 9
  • High School
Language
English
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

HS-PS2-6 Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.

Clarification Statement: Emphasis is on the attractive and repulsive forces that determine the functioning of the material. Examples could include why electrically conductive materials are often made of metal, flexible but durable materials are made up of long chained molecules, and pharmaceuticals are designed to interact with specific receptors.

Assessment Boundary: Assessment is limited to provided molecular structures of specific designed materials.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
The activity of creating a variety of plastics of varying strength and flexibility provides a good example of understanding the role of molecular-level structure for to the functioning of designed materials. To emphasize this concept, it is important to engage students in thinking about how desired properties are achieved in the design of polymers. During the post-lab discussion, teachers should emphasize questions of understanding the ratio of amines-to-epoxy optimize strength/flexibility and what stoichiometric ratio between the epoxy and amine that corresponds with and why. Encourage students to refer back to the bridge analogy when explaining their reasoning.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Students make a claim about how the ratio of epoxy to amine hardener affects the strength and flexibility of the resulting polymer. To better emphasize the use of scientific knowledge in combination with the student-generated evidence from the lab data, teachers should ask students to defend their claim with an explanation for why the pattern in the data is reasonable based what is known about how the polymer forms in the given reaction. Students can use information about polymers provided in the “Close Encounters of the Polymer Kind” lesson that precedes this lab and the “Chemical Bridges” slides provided in the presentation materials in the current lesson to explain the pattern in the data and justification for the design of polymer materials with specific properties.

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
Students examine the data from the flexural tests of the thermoset material they have developed to identify the design characteristics of the polymer that optimize for strength or flexibility. The post-lab questions ask students to address questions about this. A discussion of results should include opportunities for all students to connect the results of the flexural tests to an understanding of using these results to designing a polymer material to meet specified criteria. The lesson could then be extended to allow for students to test their optimized design solutions to the criteria.

Disciplinary Core Ideas

This resource was not designed to build towards this disciplinary core idea, but can be used to build towards it using the suggestions provided below.

Comments about Including the Disciplinary Core Idea
The discussion resources and student questions included in this lab activity include the analogy of comparing polymers to molecular bridges. A closer analysis of the bridge analogy would allow the discussion to go deeper to understand how different functioning molecules are created due to the interactions between the varying ratios of epoxide and amine reactants. It would be valuable to reference the Chemical Bridges slide from the lesson presentation materials for this discussion. In order to fully address this disciplinary core idea, the discussion of the reaction will need to more deeply explore how the properties of the designed materials are a result of the attraction and repulsion forces at the atomic scale.

Crosscutting Concepts

This resource appears to be designed to build towards this crosscutting concept, though the resource developer has not explicitly stated so.

Comments about Including the Crosscutting Concept
The questions posed in the lab ask students to consider the pattern, or general trend, observed in the class data showing how the strength and flexibility of the thermoset varies based on the ratio of epoxy to hardener used in creating the material. To further emphasize how the information is used by engineers, students should be presented a design challenge at the start of the activity, designating particular criteria desired for a new material. Then, after analyzing the class data, students would specify the ratio needed to meet the design criteria. If sufficient materials are available, students could also create the final material in the ratio they selected and then test the material against the criteria.

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
A tip above describes ideas for better supporting students in making a claim about how the ratio of epoxy to amine hardener affects the strength and flexibility of the resulting polymer. It is important to emphasize the relationship between the polymer’s molecular structure and the observed properties of a sample. Information about polymers provided in the “Close Encounters of the Polymer Kind” lesson that precedes this lab and the “Chemical Bridges” slides provided in the presentation materials in the current lesson are resources that can be used to support students in making that connection.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This resource is an opportunity for students to use knowledge of polymers together with evidence generated from the lab activity to propose a design solution to a problem. Patterns in the lab data is emphasized as a crosscutting concept connecting the investigation to the design process, helping to demonstrate the relationship between science and engineering. Teachers are encouraged to consider how to further emphasize the understanding of the core idea of why different properties result from changing the ratio of reactants used in the synthesis reaction and how the resultant polymer structure relates to those properties.

  • Instructional Supports: Students are initially engaged in thinking about the varying properties of plastics they are familiar with in their everyday experiences. The lesson could better build on the prior knowledge of students by presenting them with a design challenge with criteria needed to drive their investigation of the properties of the polymers created through the reaction between the epoxide and amine. A teacher could introduce the design challenge by having students examine sample plastic materials available in the classroom to describe what properties differentiate the different plastics and what properties would be important within their design challenge - a selection of plastic products would need to be supplied by the teacher. This would also allow the teacher to further differentiate the lesson for learners at different levels. The design challenge would provide an opportunity for students to develop deeper understanding of the work of material scientists in designing materials to meet specific needs in properties - a key idea in the disciplinary core idea in the performance expectation. Moreover, using some samples of other plastic materials and understanding of their properties may allow for students to design their own tests of physical properties of the polymer samples they create in this experiment to use in addition to or in place of the given tests.

  • Monitoring Student Progress: Questions are provided to assess student proficiency using, class discussion and written lab work. Teacher should consider opportunities for formative assessment for monitoring student progress throughout instruction that emphasized the disciplinary core idea and crosscutting concept, including during the experiment and data analysis. This may include holding short conferences with each group, posing questions such as, during the synthesis of the polymer: “how do the properties of the polymer differ from the properties of the reactants? how can you account for the differences?” and while groups are analyzing the class data:“what patterns do you notice in the data?” or “what does the data mean for designing new materials?” and then following with further probing questions to uncover students’ thinking. The conferences provide an opportunity for the students to prepare to communicate their results during the whole class discussion and provides the teacher with data to use in planning appropriate ways to support students in practices of argumentation in ways that connect to the disciplinary core ideas and crosscutting concepts and provide ongoing feedback to students.

  • Quality of Technological Interactivity: This review pertains to the written lab activity and not additional reference materials linked from the resource.