Plastic Polymers: Investigating Their Flexibility

Gloria Brandt, Grade 3
Oak Crest Elementary - Belle Plaine, MN
Based on a unit of study from the Houghton Mifflin Science Series (2007) - chapter titled "Matter Changes", pages E2-E29.
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Summary

Students will use their prior knowledge about atoms and molecules plus changes of matter, including physical and chemical changes, from the Houghton Mifflin science curriculum. Students will create a hypothesis to test the physical properties of materials such as plastic (polymers) and how its chemical properties allow it to have unique physical properties.

Learning Goals

This activity is designed for students to:
  • Develop a hypothesis and take part in a controlled scientific experiment
  • Compare data and draw conclusions based on the experiment
  • Apply the knowledge to their daily life


Process skills used in the investigation include: observing, questioning, comparing, predicting, and recording.

Context for Use

Grade level - 3-5: Groups of 2 or 4
Class size 24-30; Rural Public School Facility
2-3 lessons (including Lecture/Vocabulary, Classification Activity, Model Building, Experimentation, Application, and Assessment)

The experiment part of the lesson may be conducted indoors using tubs or sinks to catch water, or may be conducted outdoors if weather permits.

This activity is to build upon and enrich their prior knowledge of atoms and molecules as they relate to physical/chemical properties and changes.

Description and Teaching Materials

Materials

Plastic examples from students' homes
Polymer Pet head and body form with magnetic backs
Balloon
Plastic Ziploc bags
Long, sharpened round-edge pencils
Water
Containers to catch water in (large plastic tubs)
Science notebook
Ball of yarn

Experiment & Demonstration

Review with students what is a polymer and characteristics they show (dense, strong, and flexible). Also review the Polymer Pets and how their chain-like structure stays connected yet can be moved by other objects. Demonstrate with a magnetic version of a polymer pet on the board. Share with the students how we are going to investigate the properties of polymers with a balloon and air & a plastic bag full of water and a pencil.

Introduction activity

  • Show a balloon with air and ask what would happen if we pushed a sharpened pencil through it? Have students write down their predictions in their science notebook.
  • Demonstrate to them what happens. Discuss the results. Have students write down their observations in their notebook as well.

Experiment

  • Start a basic O/K/W/H/L chart on the Smart Board as students also create one in their science notebooks (guiding them through the observations, knowledge, want to know sections).
  • Take a Ziploc bag and inflate it by blowing air into it and then seal it. Write down observations and predictions. Push a pencil through the bag. Discuss what happened and again write down observations.
  • Unseal the bag and half fill it with water. Zip it closed. While holding the bag over a plastic tub or container, have students try inserting a pencil through a bag of water so the point goes in one side and out the other (or ask a volunteer). What happened to the water in the bag? Add more observations to the chart. (Polymer chains with their flexibility and strength allow the material of the baggie to mold around the pencil and keep water from pouring out).
  • While the bag is still over the plastic tub, slowly remove the pencils. What do they observe? Can we reverse the process? (Polymers are not capable of sealing themselves back together).
  • Allow students to hypothesize about other things they could try on the plastic bag (to test polymer structure) - examples: place more pencils through bag, different positions, different objects, amount of water, different bag types.
  • Regroup to discuss hypotheses tested and what they learned.
  • If possible use a ball of yarn to show how yarn can be pierced by a pencil and the fibers remained gathered together around the pencil.

Web sites
http://www.americanchemistry.com/s_plastics/hop_jr/activities
http://web.archive.org/web/20111215045930/http://www.stevespanglerscience.com/experiment/00000049
http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/polymer.html

Books
Jancie VanCleave's 204 Sticky, Gloppy, Wacky, & Wonderful Experiments. 2002 Jossey-Bass.

Houghton Mifflin Science (2007).

Lilly's Purple Plastic Purse by Kevin Henkes

http://www.americanchemistry.com/s_plastics/hop_jr/activities

http://www.stevespanglerscience.com/experiment/00000049

http://www.reachoutmichigan.org/funexperiments/agesubject/lessons/polymer.html

Teaching Notes and Tips

Students need to be reminded that this is a hands-on scientific investigation and that appropriate behavior and handling of materials (especially water) is expected. Also note that when puncturing the bag the pencil should enter and exit the bag in one straight motion. The plastic bag does not leak when the pencil point is pushed through one side and out the other in one continuous motion. Removal of the pencil shows that the hole left by the pencil appears stretched around the edges (not torn) and is slightly smaller in diameter than that of the pencil.

Assessment

Students can be assessed in the following way:
  • Science journal (observations, questions, hypothesis, data, and response to hypothesis)
  • Completion of O/K/W/H/L chart in science notebook

Standards

3.1.A.1 (Scientific World View) Student will explore the use of science as a tool that can help investigate and answer questions about the environment.

3.1.B.1 (Scientific Inquiry) Students will ask questions about the natural world that can be investigated scientifically.

References and Resources