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Mystery Powders

Grades: 5-8
Author: Diane Salamon
Source: Original


Abstract

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.


Objectives

What should students know as a result of this lesson?

  • Students will state that some natural substances are polymers
  • Students will describe and give examples of a physical change is

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

  • Students will safely handle unknown substances
  • Students will make hypotheses
  • Students will record physical properties of matter
  • Students analyze observations and form conclusions
  • Students work in cooperative groups

Materials

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.


Procedures

Engagement

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.

Exploration

  1. Hand each group a sheet of wax paper that has eight sections drawn and numbered on it. (egg carton can be used in place of wax paper)
  2. Place wax paper on a cafeteria food tray.
  3. Each group measures half a teaspoon of each substance and places it on their wax paper in the appropriate numbered square.
  4. Students write observations of the dry powders in the appropriate part of the data sheet (see attached)
  5. Each group has a small cup of water, a few toothpicks, and a pipette or dropper. Students add about a half teaspoon of water one at a time to each substance. Use the toothpicks to stir the powder and water, but do not contaminate from one square to another. Some substances are super absorbers and the students can keep adding water to them. (#2 & #8)
  6. Each group will record their observations on a data sheet. Record observations after adding water. Students are required to use descriptive terms. Ex. Grainy, crystal, smooth, silky, sticky.
  7. Groups will make inferences to try to identify the polymers.

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.

Explanation

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.

Elaboration

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:

  1. What are the physical properties of dry powdered cornstarch?
  2. What are the physical properties of cornstarch after water is added and mixed into it?
  3. Hypothesize or elaborate on why or how water can change the physical properties of cornstarch.

Prerequisites

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.


Best Teaching Practices

  • Learning Cycle
  • Hands-on/Minds-on Learning
  • Science Process Skills

Alignment with Standards

NGSS Standards:

  • MS-PS1-1 Develop models to describe the atomic compostion of simple molecules and extended structures.
  • MS-PS1-2 Analyze and interpret data on the properties of substances before and after the substances interact to determine if a chemical reaction has occurred.
  • MS-PS1-3 Gather and make sense of information to describe that synthetic materials come from natural resources and impact society.

Common Core Standards:

  • RST.6-8.1 Cite specific textual evidence to support analysis of science and technical texts.
  • RST.6-8.3 Follow preciesly a multistep procedure when carrying our experiments, taking measurements, or performing technical tasks.
  • WHST.6-8.2 Write informative/explanatory texts, including the narration of historical events, scientific procedures/experiments, or technical processes.

National Standards:

  • Content Standard B
  • Content Standard E
  • Content Standard F
  • Content Standard G

Ohio Standards:

  • Physical Science: 6th, #2 and #4
  • Scientific Inquiry: 7th, #2 and #7

Content Knowledge

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.


Safety

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.


Applications

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!


Assessment

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.


Other Considerations

Grouping Suggestions: Two to four students to a group.

Pacing/Suggested Time: 40 minutes.


Printable PDF Worksheets

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