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Akron Global Polymer Academy Lesson Plans

Stretch Your Students' Imaginations - Rubber Band Contest

Grades: 5-8
Author: Dr. Carin A. Helfer
Source: Original


Abstract

Students will explore the properties of polymers using a poly putty made from glue and borax. Physical and chemical changes, conservation of energy, and kinetic friction will be explained. An extension of the lesson allows the students a fun opportunity to enter the AGPA Rubber Band Contest for Young Inventors. The entire lesson allows teachers to meet science content standards and introduce polymers and science concepts using the Best Teaching Practices Hands-On/Minds-On Learning and Authentic Problem-Based Learning.


Objectives

What should students know as a result of this lesson?

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


Materials


Procedures

Engagement

In advance of class, make a batch of the poly putty at 60% glue concentration (see Table in Exploration section). For a video on making poly putty, see below:


At the beginning of class, show the students the poly putty. Ask the students if they had previously made or seen glue putty. If so, ask them to describe this material. Write their comments on the board.

Next, make a ball with the putty and ask the students what they expect will happen when you drop the ball a set height from the table. Drop the ball to determine if it meets their expectations.

Explain to the students that you made the poly putty with 60% glue and 40% water. The concept of concentration will need to be explained at the appropriate level for the age of your students. Ask the students, "What do you expect will happen if the glue concentration is 75%? What will happen if the glue concentration is 50%?" Write their guesses on the board.

Tell the students that they will work in groups to make poly putties of different glue concentrations to investigate the materials' properties.

Assessment: The assessment is informal at this stage. The students should all be involved in the discussion.

Exploration

  1. Students can be placed in groups of 2, 3, or 4, whichever works best for your class.
  2. Pass out worksheets to each student.
  3. Assign each group a sample number that determines the concentration of glue as given in the table below.

Stretch Your Students' Imaginations Lesson

Measuring the glue and glue dilution:

  1. For measuring the glue, it is best to use a small plastic cup that has been marked for 42 ml. First, use the graduated cylinder to measure 42 ml of water. Transfer water into the small plastic cup and mark with a permanent marker a line at the level of 42 ml. Dump out the water after marking the cup.
  2. Use the marked cup (with line for 42 ml) to measure the glue. Dump the 42 ml of glue into a large plastic cup.
  3. Measure the necessary amount of water for your sample choice in the graduated cylinder and add this water to the glue in the large plastic cup. Stir with craft stick.
  4. Food coloring can be added to the glue and water. A drop or two is sufficient.
  5. Have the students record the selected concentration on the worksheet.
  6. Have the students record observations of glue and water on the worksheet.
  7. Have the students answer the question regarding physical or chemical change on the worksheet.

Note: the different concentration of glue will result in poly putties with different final properties.

Making the borax solution:

  1. Fill the plastic cup for the borax solution with 120 ml (approximately 1/2 cup) of warm water.
  2. Add 5 grams (approximately one teaspoon) of borax powder to the water. Stir with a spoon until nearly all of the borax powder is dissolved. Note that some borax will remain out of solution.

Making the Poly Putty:

  1. Have the students use the measurements in the table below to determine the amount of the borax solution to add to the glue and water solution.

Stretch Your Students' Imaginations Lesson

  1. Using a graduated cylinder, measure and add the appropriate amount of borax solution to the cup filled with glue and water.
  2. Stir the mixture until it reaches a point that it can be removed from the cup and kneaded.
  3. Have the students answer the question regarding physical or chemical change on the worksheet.
  4. Have the students describe the properties of the poly putty on the worksheet.
  5. Have the groups break their poly putty into two pieces and trade one piece of their poly putty with another group to examine a poly putty made with a different concentration of glue. You should have the trades pre-determined so that each group will have a concentration that differs from their original concentration.
  6. Have the students compare the properties of the poly putty that they made with the properties of the poly putty made with a different concentration of glue on the worksheet.

Assessment: See that students are following proper laboratory procedures. Monitor the groups and make sure they are recording all their observations and data.

Explanation

As a class review/discuss the worksheet.

  1. Water added to the glue is a physical change. The water can be evaporated to return to the glue, if desired.
  2. Borax added to the water is a physical change. The water can be evaporated to return to the borax powder.
  3. Adding the borax solution to the glue and water is a chemical change. A crosslinked network forms with hydrogen bonds being formed.

See: http://chemistry.lsu.edu/site/Outreach/item1739.pdf for additional information on the chemistry that occurs when making poly putty.

Physical change: A new substance is not created, only the form of the substance is changed. Physical changes can be reversed.

Chemical change: A chemical reaction occurs and a new substance is formed. Chemical changes cannot be easily reversed. Energy is either given off or absorbed during the process. See: http://www.ric.edu/faculty/ptiskus/chemical/ for additional information.

Conservation of Energy: Remind the students of the beginning of the lesson when you dropped the ball of poly putty on the table. Use this event to discuss the conservation of energy: the gravitational potential energy was converted to kinetic energy. Gravitational potential energy is the energy that an object possesses because of its position in a gravitational field. Kinetic energy is the energy of an object because of motion.

For older students, the elastic potential energy is the potential energy that an object possesses because of its deformation. When a rubber ball is dropped, the gravitational potential energy converts to kinetic energy, as mentioned above. The ball bounces back up because on impact the kinetic energy converts to elastic potential energy as the ball compresses. This elastic potential energy then converts into kinetic energy. The ball does not return to its original height because as the ball compresses, some energy is lost to thermal energy.

For #4 and #5 of the worksheet, the students will have various properties of the poly putty to share. Polymers are quite unique materials. The AGPA's "What are Polymers?" multimedia presentation at http://uakron.edu/cpspe/agpa-k12outreach/what-are-polymers/multimedia-presentation-intro-to-polymers/whatarepolymers.html is a good introduction to polymer materials.

Rubber elasticity - the ability to undergo large deformations of the material and completely recover (think of a rubber band).

Polymer flow - the students should have observed that when a ball of putty is set on the table, over time the ball will flatten as the chains slide past each other under the force of gravity.

High coefficient of friction - The students may not have thought about friction when observing the poly putty. If the students did not mention this property in your discussion, ask them if the putty is easily slid on the desktop. Discuss why many sports shoes have rubber soles. Kinetic friction is a force that occurs when two objects in contact interact by sliding past one another.

Assessment: An informal assessment can be done, such as an oral review of the concepts presented. Alternatively, or in addition, a traditional assessment, such as a short quiz, can be done to determine if the students understand the concepts presented.

Elaboration

As a final project, have the students create an invention to enter in the AGPA Rubber Band Contest for Young Inventors. See http://rubberbandcontest.org/ for Official Rules and Entry Form.

Entries entered in the Science & Engineering Division will challenge the students to do engineering design. The Engineering Design process differs from the Scientific Method and includes the following steps:

Stretch Your Students' Imaginations Lesson

Assessment: A rubric is included for grading the students' inventions and essays. The students can also give oral presentations to explain their inventions to the class.


Prerequisites

Students need to know how to use a graduated cylinder. See:


Best Teaching Practices


Alignment with Standards

NGSS Standards:

Common Core Standards:

National Standards:

Ohio Standards:


Content Knowledge

Content knowledge added into Learning Cycle as appropriate. Additional basic polymer information can be found at The Macrogalleria, a Cyberwonderland of Polymer Fun: http://www.pslc.ws/macrog/maindir.htm


Safety


Applications

Polymer materials, both naturally occurring and man-made (synthetic), are very significant to our everyday lives. Therefore, understanding these unique materials and their properties is important.

Friction is a science concept that we encounter every day.


Assessment

Using the Internet or library resources, have students research an item that did not exist 50 years ago. Have the students should report to the class the benefits to society of this invention and possible disadvantages because of the invention.


Other Considerations

Grouping Suggestions: Ideally, small groups of students are preferable to allow the students more hands-on experience. However, the students can be placed in groups of 2, 3, or 4, depending on what works best for your class.

Pacing/Suggested Time: 45 minutes for Engagement, Exploration, and Explanation. If the students will work on their rubber band inventions in class, multiple 45-minute class periods will be necessary.


Printable PDF Worksheets

Stretch Your Students' Imaginations Worksheet

Stretch Your Students' Imaginations Rubric