Home Experiment #1

Second Semester: 2008

Plastics and Recycling

You will be doing two home experiments this semester. Each one will count 75 points.

The total number of points earned on the two home experiments will be recorded at the end of the semester.

Purposes

• To learn about polymers

• To learn about how plastics are made
• To learn about the different types of plastics

• To test different types of plastics and see if they can easily be separated on the basis of differing densities.

Directions

For the background section of the project (pages 1-3) type the answers below the question and print the pages. Then write up the lab report (see last page for requirements) and attach the two halves. NOTE: TYPE THE ANSWERS TO THE QUESTIONS IN BOLD FONT OR ANOTHER COLOR (IF YOU HAVE A COLOR PRINTER) TO DISTINGUISH THEM FROM THE QUESTION.

Note: Your textbook is a good source of information on basic polymer chemistry.

See pages 1084-1089.

Background

1. Plastics are types of polymers. Define polymer. Include the relationship (or difference) between a monomer and a polymer.

2. Polymers can be natural or man-made. Give examples of two natural polymers and two man-made polymers.

1. Natural-

2. Man-made-

    3. Polymers can be classified as addition polymers or condensation polymers depending on the type of reaction used to form them.

            A. Addition polymers: An example of an addition polymer is polypropylene used to make bottles, carpets and textiles. Show the reaction of 3 monomers of propylene to form a short chain of polypropylene. (See textbook. You may want to draw this by hand.)

            B. Condensation polymers: Condensation polymers are formed when the –OH group of one monomer reacts with the –H of a neighboring monomer to form water. When the water molecule forms, the two monomers covalently bond to each other.  Give two examples of condensation polymers.

      4. Plastics are polymers. Many plastics are made from the monomers ethylene and propylene. The monomers ethylene and propylene come from crude oil. List four other products or items around the home that are produced from various components of crude oil.   http://www.priweb.org/ed/pgws/uses/uses_home.html

     5. Different plastics are made by combining different monomers. Changing the chemical make-up of the monomer can completely change the properties of the plastic produced. Using your textbook, draw in the monomers used to make these plastics and some common uses.

6. Once the tiny beads of polyethylene or polypropylene are made, they can be turned into plastic items using three main methods. Briefly summarize the methods below and what types of objects/items are made using each method.

 http://www.teachingtools.com/Slinky/methods.html

http://www.plasticsresource.com/s_plasticsresource/sec.asp?TRACKID=&CID=126&DID=228 (end)

            A. Extrusion molding:

            B. Injection molding:

            C. Blow molding:

       7. There are six categories of plastics involved in recycling. Each type is given a different recycling code that can often be found on the bottom of the container in a triangle or surrounded by arrows. Fill in the chart below listing each type of plastic including its code number, chemical name, abbreviation and uses. The first one has been filled in for you. Look at each site for a wide range of uses. For your experiment, you will need a sample of each so the more examples, the better!

http://www.eia.doe.gov/kids/energyfacts/saving/recycling/solidwaste/plastics.html

http://www.wastecare.com/Information-Links/a2-types-of-plastics.htm

http://scifun.chem.wisc.edu/chemweek/polymers/polymers.html (good list at the bottom)

Comparing Plastics

An Experiment

Background

To reuse plastics, we have to separate different types of plastic from another so all compatible plastics can be combined into one group and reprocessed as a whole. One way to sort them is to take advantage of the differences in their densities. In this experiment, you will attempt to separate a series of plastics by placing them in various liquids and observing whether the plastic sinks or floats in each liquid. (If the plastic floats, its density was less than that of the liquid. If the plastic sinks, its density was greater.) You will also be comparing the plastics’ transmission of light and flexibility.

Purpose

To compare 6 categories of recyclable plastics in terms of their transmission of light, finish and density.

Materials

A sample of each type of plastic (Code 1 to Code 6) each cut into a 2 cm x 2 cm square

            (Using a permanent marker, write the corresponding code number on each sample. You will    turn these in to your teacher at the end of the experiment). Record the source of each plastic 

(milk jug, etc.) for your data table.

4 medium sized drinking glasses

1 bottle of rubbing alcohol (obtained from a grocery store or pharmacy)

Salt

 Procedure

1. Transmission of Light: The six plastics vary in how transparent or opaque they are.

        A. For each plastic classify its ability to transmit light as one of the following:

a. transparent- can easily see through the plastic

b. opaque- cannot see through the plastic at all

c. translucent-can see through the plastic a little, but it’s somewhat cloudy.

        B. For each plastic, classify its finish as one of the following:

a. glossy-shiny

b. matte- not shiny

2. Flexibility:
Test the flexibility of each plastic i.e. how easily does the sample bend? As you bend the samples, observe if fine lines appear in the plastic after bending. The formation of these lines is called “crazing”.

Classify the flexibility of each plastic according to the following choices:

     a. Rigid, brittle- these would be hard to bend and might snap when bent

     b. Stiff but will bend

     c. Flexible-easily bent

     d. Crazes- bends forming lines in the plastic

3. Density Test:

A. Prepare the four glasses with the following:

1/2 cup of rubbing alcohol (Density of rubbing alcohol = 0.94 g/mL)

1/4 cup of rubbing alcohol and 1/4 cup of water (Density = 0.97 g/mL)

1/2 cup of water (Density of water = 1.00 g/mL)

1/2 cup of water containing 2 teaspoons of dissolved salt (Density = 1.20 g/mL)

B. To the cup of rubbing alcohol, add the Code 1 plastic. Does it sink or float? (Put the plastic in the liquid, edge first, or push it below the surface with your finger so it is not floating on the “skin” at the surface of the water i.e. make sure you break the surface tension of the liquid!) Record your observations. Remove the plastic, and test the other six samples. Record your observations. Dry off the samples of plastic before testing them in the next step.

C. To the cup of 50:50 alcohol/water, add each of the samples (one at a time), and record your observations. (Does the plastic sink or float?)

D. Test your samples in the water and then the salt-water solution, as before. Record your observations.

E.  The liquids may be discarded in the sink.

F. PUT YOUR PLASTICS IN A ZIP-LOCK BAG TO TURN IN TO YOUR INSTRUCTOR.

Lab Report

Title

Purpose

Data Tables

Table 1: Include a data table with columns for

• The plastic code
• Source of plastic (milk jug, saran wrap, etc)

• Transmission of light (use descriptions given in the directions)
• Finish (glossy or matte)
• Flexibility (use descriptions given in the directions)

Table 2: Include a table that indicates for EACH plastic tested:

• whether or not it sank or floated in EACH liquid or mixture
• The range for the density of each plastic (i.e. a minimum and maximum value).

Post-Lab Questions

            A. When the plastics you recycle get to the recycling plant, they must first be separated. Using the results of your experiment, explain how various plastics can be separated from the others based on their relative densities.

            B. For three of the plastics tested, describe how one of its properties (density, transmission of light, finish or flexibility) makes that plastic ideal for its particular use(s).

TURN IN TO YOUR INSTRUCTOR

1. Pages 1-3 with answers inserted.

2. Lab report

3. Zip-lock bag with plastic samples.

Sources: experiment adapted from  http://faculty.dbcc.cc.fl.us/swansoj/Plastics_and_Recycling.htm

                                       http://www.elmhurst.edu/~chm/onlcourse/chm110/labs/lab6H97.html