Author: Diane Salamon
Students will observe physical changes by adding water to eight different polymer powders. They will record physical properties before and after adding the water. Students will analyze their observations to identify the powders. They discover polymers are more than just plastic.
What should students know as a result of this lesson?
What should the students be able to do as a result of this lesson?
Measuring spoons, cups, wax paper, droppers or pipettes, goggles, plastic gloves, toothpicks, permanent markers, water, posters of polymers, observation sheet, pencils, Ziploc sandwich size bags, food coloring, food trays or egg cartons.
A selection of natural and manmade polymers, such as: cornstarch, white corn meal, parmesan cheese , flour, baby rice cereal, clear gelatin, Ghost crystals, "artificial snow", instant potatoes.
Pre-bag polymers. #1 flour #2 ghost crystals #3 parmesan cheese #4 gelatin #5 white corn meal #6 cornstarch #7 baby rice cereal #8 "snow". Bags should be numbered but the labels kept hidden during the first part of the lesson.
Divide students in groups of two to four. Show pictures of the molecular structure of polymers on posters (cellulose, proteins, and starch). Have brief descriptions and definitions of polymers. Also have descriptions of physical and chemical changes. (This information placed on a tri-fold board.) Show students the 8 different polymer powder bags (numbered, but with labels hidden) and tell them they will determine the identity of each.
Assessment Pose this question to the students, "How will you determine the identity of these polymer powders?" The responses should include observations of the powders physical structures.
Discuss these safety issues: never touch, taste or smell an unknown substance - students must wear plastic gloves to handle the powders, students must wear protective goggles, and they may not smell the powders.
Assessment Monitor students' work to check that they are carrying out procedures carefully, making observations, and recording data accurately. Make certain that students are following safety procedures.
Each group discusses their observations and then shares their inferences with the class. Have groups collaborate together and agree on what the substances are called/named.
Share the identity of the polymers. (Place on the back of the tri-fold board.)
Assessment Ascertain students' knowledge of the powder identities by asking them how they determined what they called/named each one. Ask students how previous knowledge or use of the polymer powders is beneficial in identifying them.
Groups create Oobleck. Each group receives a Ziploc bag with a 1/2 cup of cornstarch. They add 1/8 cup of water and a few drops of food coloring. Ziploc the bag and mix or knead with their hands. They should touch the Oobleck after it has been mixed. (Oobleck is great to make when reviewing the states of matter)
Assessment Ask students the following questions:
Students will have had a lesson on lab safety rules.
Students should know how to measure.
Students should know that plastics are polymers.
Students should know that many substances are found in nature and others are manmade.
Common Core Standards:
Physical changes involve the change of a substance but no reaction occurs. A change in size state or appearance but appears to be the same matter. Examples: ice-water-vapor, changing your cloths, cutting your hair.
Chemical changes are changes in a substance through chemical reactions. The chemical reactants form a new product with equal mass. A change in the state of matter occurs. Examples: rust, fireworks, fall leaves.
Polymers are made up of many many molecules all strung together to form really long chains.
Glucose (starch) is a polymer. Examples: potatoes, bread, rice, wheat, flour, and pasta.(flour, corn meal, corn starch, baby rice cereal)
Protein (polyamide) is a polymer. Proteins are polymers of amino acids.(parmesan cheese, gelatin)
Cellulose is a polymer. Examples: paper, cotton, plants like carrots, apple trees, and flowers.
Ghost crystals are cross linked modified acrylic polymers. They are also recognized as super absorbers.
"Artificial Snow" is sodium polyacrylate. This is also recognized as a super absorber.
Enforce safety rules. Students must properly handle unknown substances; students must wear gloves (non-latex preferred) and goggles. Never touch, taste or smell an unknown substance. Have Materials Safety Data Sheets (MSDS) information on all powder substances. MSDS sheets can be obtained from Flinn Scientific (www.flinnsci.com). At end of activity wipe hands and work surface with wet wipe cloths; dispose afterwards.
Physical and chemical changes happen numerously in our daily lives. Polymers come from nature, some plants and animals have polymer chains and even our DNA!
Teacher observes and monitors activity. Group observation sheets are turned in. Students write an ESN paragraph. (Mary Harris Polymer Ambassador). Students write at least one sentence for each letter.
E - Explain the purpose of the experiment.
S - State the results of the experiment with data.
N - Name two new ideas that you learned.
Grouping Suggestions: Two to four students to a group.
Pacing/Suggested Time: 40 minutes.