Author: Sandy Van Natta
Students discover the effect of placing additives in a glue-based putty to alter the physical properties of the putty. They are then challenged to use their knowledge to design the best bouncing ball possible from the simple materials available to them.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
For the engagement demonstration:
For all other sections, at least several of the following:
For all groups:
Note: A saturated solution of laundry borax in water is needed for the activities below. To make a saturated solution add the borax to warm water while stirring. Keep adding the borax until no more powder dissolves, and the borax starts to settle out on the bottom of the container or dissolve 20 g of borax in 500 mL of water.
In this phase, you want students to start thinking about what types of materials are used in the manufacture of balls, as well as, what might make some balls bounce higher than others. Tell students you are going to drop a number of different objects and have them predict if the objects will bounce. If they predict the object will bounce, ask them to predict how high or how well the object will bounce.
You may want to title your demonstration "Will It Bounce?" Place a meter stick perpendicular to the surface on which you will drop the objects. Drop (do not throw down) all of the objects from the same height next to the stick. Allow your students to make quick visual observations of the height of the bounce of each object. The meter stick can be used as a reference for determining the height of a bounce.
Students will probably accurately predict which objects will bounce but may have trouble predicting which will bounce the highest. Use the students' observations to divide the objects bounced into two groups, the poor and the good bouncers. Students will determine the criteria for "good" and "poor" bouncers. Lead the discussion toward examining the properties of the better bouncing objects. Students should conclude that the better bouncers are all made out of some type of elastic material. Depending on their background, students may even describe the elastic materials as some type of polymer.
Assessment: Assessment is informal at this time. Have all students to write down their observations during the bounce tests and encourage them to take part in the follow-up discussion.
Tell students that the temperatures and conditions needed to form many elastic substances, found in balls used in the demonstration, are difficult or impossible to reproduce in the classroom. However, they are going to make their own elastic substance, a glue putty, from glue, water, and laundry borax. They will then be asked to determine how well the glue putty bounces. They will also be asked to make some modifications to the putty and determine if the "bounce" is altered.
Goggles should be worn at all times when making and working with the putties. If any chemical in this activity should contact the eye, rinse the affected area with water for 15 minutes and seek medical attention.
There is usually no danger in handling the glue putties but students should wash their hands after use. Borax may cause allergic reactions in some people. Students can determine their sensitivity to the putty by touching a small amount. If redness or itching occurs, wash the affected area with mild soap solution and avoid further contact.
Students may work in groups of 3 to 4 for the following procedures:
Making Basic Glue Putties
Additives for Glue Putty:
Have students make at least 2 additional putties using additives such as oil, talcum powder, and calcium carbonate.
Assessment: Make sure students are following proper laboratory procedures. Monitor students and make sure they are recording information on their worksheets.
After completion of testing, recording of data, and drawing graphs, students should report their findings and determine if the additives in the putty had any affect on the bounce height. There are no wrong answers here as long as students can back up their statements using evidence for their data and graphs. However, students will probably find that the 75/25% putty bounces higher than the 50/50% putty. The additives placed in the 50/50% putty will only have a slight affect on the bounce. Point out to students that the amount of water can be considered an additive also.
You may now wish to discuss the glue itself, pointing out to students that it is a polymer called polyvinyl acetate. Polymers are long chain-like molecules made up of repeating units. The original glue chains were sticky and runny. Adding the borax, a crosslinker, tied some of the polymer chains together, restricting their flow and creating the putty like material students worked with. The crosslinking of the polymer is an example of a chemical change. The polymer chains are bonded together changing the properties of the polymer to make it more viscous (flows more slowly) and more bouncy.
When industry adds a chemical to alter the final properties of a polymer, it is called compounding. In this activity, students were trying to alter the amount of bounce in their polymers. Industry can use compounding to alter properties such as strength, color, electrical conductivity, fire resistance, UV light resistance, and even to reduce static "cling".
If you wish, you may talk about the actual bouncing of a ball. A ball has potential energy at the top of its bounce. The potential energy is converted to kinetic energy as it falls toward the ground. After collision with the ground, the ball rebounds but does not return to its original height. This is due to the fact that some of the energy in the bounce is converted to sound and heat during the collision. The ball itself also deforms during a collision. The ball must reform before energy can be returned to the bounce. The more the ball stays deformed, the less kinetic energy is available for the bounce.
Challenge the students to make the best bouncing ball possible using a basic glue and borax mixture with or without the addition of other additives. Place all the additives and items you think the students might wish to use on a table.
You will need to have some basic rules to maintain order and consistency in the classroom. Suggested rules are given below:
Allow your students to be creative in this stage. They may want to try a straight glue and borax mixture without water or alter the amount of borax solution used. They may wish to put oil and talcum powder in the same mixture. They may wish to put rubber bands in the core of their ball or wrap their ball in plastic wrap to help keep its shape. Since it will take time for students to make and test all their putty balls, have students keep their formulations in zipper type plastic bags overnight. Remind them to clearly label the contents on the bag with a magic maker. Each individual bag can be placed in a larger plastic bag so that all the groups' samples are stored together between classes.
Assessment: Have students write a short report of their findings. This report can be given orally to the class. If an oral report is given, have students show any graphs or data tables created to back up their findings.
An Alternative Elaboration: Have students search the web to find how various types of balls are made as well as their individual characteristics.
Assessment for the Alternative Elaboration: Students can then compose a report on their findings. You may choose to have students report their findings orally to the class.
Students need to be able to read a ruler, perform simple math calculations and draw graphs.
Common Core Standards:
Students can find information on the make up of different types of balls and how they relate to a given sport on the web.
The simplest definition of a polymer is something made of many units. The units, or monomers, are made up mostly of carbon and hydrogen atoms and are linked together to make a chain from at least 1000 atoms to many 1000's of atoms in a row. While some polymers, like polyvinyl acetate (Elmer's Glue) can exist in the liquid state at room temperature, they can be made more solid or gel-like by the addition of a crosslinker. A crosslinker is a small molecule or ion which bonds to two different polymer strands and restricts the movement of the individual polymer strands. This causes the characteristics of the polymer to become more gel-like and less fluid. Since a new substance is formed by the addition of the crosslinker, a chemical change has taken place.
Scientists continue to develop cheaper, stronger, and better polymers. One method of accomplishing this is through compounding, or the addition of a variety of materials to a polymer during the manufacturing process. The goal is to make the best product possible and assure trouble-free manufacturing of the product. Additives change the properties and/or improve the ease of processing the polymer. The final product performs better and can be offered at lower cost to the consumer. Additives may be fillers (extending agents), reinforcers, antioxidants, heat and ultraviolet stabilizers, flame retardants, plasticizers, colorants, lubricants, foaming agents, and antistatic agents. The borax used in this activity, a crosslinker, can be considered an additive here.
Goggles should be worn at all times when making and working with the putties.
If any chemical in this activity should contact the eye, rinse the affected area with water for 15 minutes and seek medical attention.
There is usually no danger in handling the glue putties but participants should wash their hands after use. Borax may cause allergic reactions in some people. Participants can determine their sensitivity to the putty by touching a small amount. If redness or itching occurs, wash the affected area with mild soap solution and avoid further contact.
"Used" putties can be placed in the trash. All testing equipment can be returned for re-use.
Numerous sports are based on the throwing, hitting, or kicking of balls. Some balls are designed to move through the air with great speed but bounce relatively poorly, such as a football, while bounce is more important in balls such as racket and tennis balls. Students should realize that each ball is constructed of a different elastic material with different properties. In this activity, students are learning how to alter the physical properties of an elastic polymer to gain the best bounce possible.
Tell each group of students that they are a toy manufacturer trying to market a new product, a bouncing putty. Have them design an advertising campaign that promotes the properties of their putty compared to the putties created by other groups (toy manufacturers) in their class. Students must use actual data to back up their campaign.
Grouping Suggestions: Be aware of students' abilities and ethnic backgrounds when choosing groups. Try to place students of varying abilities and backgrounds in each group.
Pacing/Suggested Time: This activity will take several 45 minute class periods. It will probably take 1 class to perform the Engagement activity and make the first set of putty samples to be tested. It will take a second period to test the samples, record and graph data, and plan the mixtures each group will try when allowed to create formulations on their own. A third, and possibly a fourth class, will be needed to test the new formulations, draw conclusions and write the assessment report.