CHM 110 - CHEMISTRY AND ISSUES IN THE ENVIRONMENT
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Home Laboratory # 6
C. Ophardt, Elmhurst College, c. 2004
PROPERTIES, CLASSIFICATION, AND RECYCLING OF PLASTICS
PRE-LAB: SOLID AND HAZARDOUS WASTE ASSESSMENT (5 pts)
:
1. Calculate/estimate the solid waste that you or your household produces on a
yearly basis.
2. Appreciate the fairly large amounts of wastes produced by your life-style.
3. Recognize methods for decreasing your production of wastes.
OBJECTIVES
INTRODUCTION :
In this exercise, you will be introduced to various solid wastes which are
produced to support the lifestyles that we are accustomed in the United States.
You will calculate the amount of solid wastes that you personally produce, as
well as, the amounts calculated on a per capita basis. The per capita amounts
are produced indirectly by you because of the manufacturing, industrial,
mining, and agricultural activity needed to support society in general. For the
per capita calculations, assume that the population of the United States is 250
million. Take whatever figure is given for the entire U. S. and divide by 250
million to get the per capita amount.
Large amounts of waste products are produced by agriculture and logging.
Much of this waste is left in place and is eventually biodegraded. However,
agricultural (animal and crop) wastes can cause serious water pollution
problems if concentrated by very large farms. Mining activities result in huge
piles of tailings, overburden from strip mines, smelter slag, and other residues.
Depending on what is done with them they can have large impacts on the
environment. A rule of thumb is that it takes 20 pounds of raw material to
produce 1 pound of useful product. In this survey, we will concentrate on
household or municipal wastes.
Source of Solid Waste: 6.67 Billion tons of solid waste produced per year
Graphic # 1:
QUES. 1: a. Calculate the total tons of waste per person per year if 6.67 billion
tons are generated nation wide. Assume a population of 250 million.
(Approx. ans. = 10-50 tons)
b. Convert the tons of waste per person per year to pounds. 1 ton = 2000
pounds.
(Approx. ans. = 25,000-100,000 pounds)
Composition of Municipal Waste: 159 Million tons municipal waste
(excluding commercial) per year
Graphic # 2:
QUES. 2: Calculate how many total tons and then pounds of municipal or
household garbage is produced per person per year.
(Approx. ans. = 500-2000 pounds)
QUES. 3: Calculate how many pounds of paper per person are thrown away
per year.
(Approx. ans. = 100-1000 pounds)
INVENTORY # 1: Weekly Garbage Survey
Devise a method to calculate the pounds of garbage thrown away for one/two
weeks. Since most of you probably have a bathroom scale, use this to weigh the
garbage. First find your weight, then hold a bag of garbage and reweigh
yourself. The difference is the weight of the garbage. Note: If you do not have a
bathroom scale, an alternative is to do some type of volume measurement for
the inventories.
QUES. 4: Weight of garbage week # 1: _______ Weight of garbage week # 2:
________
Weight of garbage per household / year: _______
INVENTORY # 2: Recycling
Another way to dispose of waste products is through recycling. An increased
public and municipal awareness has resulted in a variety of recycling efforts.
Measure the pounds of recycled materials collected in a one/two week period.
Then pro rate them to a yearly number. Choose any TWO of the following four
categories.
QUES. 5a: DATA
Material
Pounds/ week
Pounds/year
Paper
Aluminum
Glass
Plastic
Total lbs. recycling
QUES. 5b: How much do you currently recycle and what specific methods
could you use to increase the amount that you recycle?
HAZARDOUS AND TOXIC WASTE IN HOMES
Toxic commonly refers to a narrow group of substances that are poisonous
which cause death or serious injury to humans and animals. Hazardous , a
broader term, includes all wastes that are dangerous, including those that are
toxic. They present immediate or long term health risks or pose a threat to the
environment.
Legally, a hazardous waste is any discarded material, liquid or solid that
contains substances in the following four categories:
1. Fatal to humans or laboratory animals in low doses.
2. Toxic, carcinogenic, mutagenic, or teratogenic to humans or other life forms.
3. Ignitable with flash points less then 60 degrees Celsius.
4. Corrosive - Strong acid, bases, or oxidizing or reducing agents.
5. Explosive or highly reactive (undergoes violent chemical reactions).
Although most households do not accumulate large quantities of hazardous
wastes, we all have materials in our homes that are both toxic and hazardous.
Many solvents, paint thinners, old cans of paint, car batteries, flashlight
batteries, cleaners, pesticides, fuels, used motor oil, and other materials are just
as dangerous as their industrial counterparts. When we discard them in the
sewers, garbage, or on the soil, they combine with those of our neighbors to
make a significant quantity.
Develop a plan of action to safely use, store, and dispose of the hazardous
wastes in your house. Should you put them in the normal garbage for pick-up?
INTRODUCTION TO LABORATORY:
Within the last 15-30 years, a large variety of plastics have found many uses in
the consumer market including bottles and containers, wrappings, and
packaging. What happens to the millions of plastics items that are discarded
each day? There are a variety of methods to deal with this solid waste
including: source reduction, reuse, recycling, landfill, and incineration.
The purpose of this laboratory is to use both physical and chemical properties,
to identify and classify various plastic items, and finally to devise a method to
separate and recycle the plastic.
EXPERIMENTAL PROCEDURES: At home collection of lab data (Ques
6-10 - 4 points)
Characteristics of Polymers Chains:
1. Cold Drawing of Plastic Films:
When polymer films are stretched (cold-drawn), the chains orient themselves.
This is similar to the molecular changes that occur in a rubber band when it is
stretched. However, polymer films such as plastic wrap, generally are not cross
linked and thus do not have a restoring force that is observed in rubber bands.
Orientation (alignment ) of macromolecule chains also occurs during the
processing that occurs prior to use by consumers. As a result, plastic films tend
to have more of the chains lined up in one direction than the other. If polymer
chains are all aligned in the same direction, then they should stretch longer, and
more easily. In this part of the experiment, we will try to determine the
orientation of the chains in a plastic film.
a. Cut several strips about 1 in wide and about 10 in long from one edge of a
large plastic trash bag. (Carefully keep track of the direction of the cut.) Grasp
the strip firmly between the thumb and fore finger of each hand so that your
hands are about three inches apart.
b. Pull the film by moving the hands apart slowly. Notice how the sample
narrows (necks) as the molecules align within the sample. Notice any changes
in the amount of pressure required to pull the strip - initially and as the strip
necks. Continue to stretch the film until it breaks. Place the two broken ends
next to each other and use a ruler to estimate the total length that the film
stretched before breaking. Repeat the procedure one or two times to see if the
observed lengths are reproducible. length ___________
c. Cut several similar strips from the plastic bag, but along an edge that is
perpendicular to the first strips that were cut. (Carefully keep track of the
direction of the cut.) Repeat the procedure in (#b) on these strips. length
______
QUES. 6: Lengthwise stretch ________; Crosswise stretch ___________
Which strip direction in the bag were the polymer molecule chains more
closely aligned i.e. are the polymers running lengthwise or cross wise?
2. Ripping a Newspaper: A newspaper is made of cellulose polymer chains of
glucose units.
QUES. 7: Are the cellulose polymer chains in a newspaper randomly
distributed or are they aligned in a particular direction? Which direction does a
newspaper rip more easily with less jagged edges? If so which direction? Rip
the newspaper in various ways until you can answer the question. Definitions:
The vertical direction is the up/down direction as you read the newspaper. The
horizontal direction is when you rip it crossways left to right as you hold it to
read the paper.
Give the name of the newspaper you are using such as Tribune, Sun Times, etc.
Pre-Laboratory Collection of Representative Plastic Samples:
Most plastic items have a recycle code stamped or printed on them in the form
of a triangle and number. Try to find at least one sample of each of the six
types of plastics that have recycle codes. Cut the samples into smaller pieces
about 1 inch square.
QUES. 8: Use the textbook to look up the abbreviation, such as PVC, and the
chemical name of the plastic that corresponds to each recycle number.
Recycle Code
Abbreviation
and Chemical
Name of Plastic
Types of Uses and Examples
1
Clear, 2 liter beverage bottles
2
Milk jugs, detergent bottles, some water bottles
3
Saran wrap, plastic drain pipe, shower curtains, some water bottles
4
Plastic bags, garment bags, coffee can lids
5
Aerosol can tops, rigid bottle caps, candy wrappers,
bottoms of bottles
6
Hard clear plastic cups, foam cups, eating utensils,
deli food containers, some packing popcorn
-
Biodegradable, Some packing popcorn
3. Density of Plastics:
Set up one cup and put about 1/2 to 3/4 cup of water in it. Test the density of
each of the samples in the water as described below.
****At home collection of lab data ****
a. Density in Water: Drop the plastic sample into water. Try various ways of
putting the piece into the water, including pushing it below the surface if it
appears to float; so that surface effects and air bubbles are minimized. If the
sample floats, it has a density of less than 1.0 g/ml. If the sample sinks, it has a
density of greater than 1.0 g/ml. List/describe.
****All Data for Part 3 b and c are given online****
****You do not actually have to complete these procedures. Dr. Ophardt did
them for you and took pictures of the results. You should read the procedures to
see what was done, record the data, and answer the questions.*****
b. Density in Saturated Salt Solution: Test the density of the plastic in
saturated salt solution that has a density of 1.20 g/ml. List/describe.
c. Density in Rubbing Alcohol: Test the density of the plastic in rubbing
alcohol (70% isopropanol/water), with a density of 0.94 g/ml.
List/describe.
QUES. 9: RECORD the density behavior in the DATA TABLE. Such as
floats on water, sinks in alcohol, etc.
****Click on the number to get the online computer data on the behavior of
the plastics in alcohol and salt water.****
Add your own data on the density behavior in water.
Recyle Number
Abbreviation
Alcohol
Water
Salt Water
Density Range
1
2
3
4
5
6
DENSITY RANGES: From the density behavior tests, develop a range of
densities for each example of plastic. Record on the Data Table - below and
above. If the sample floats, the density is less than the solvent. If the sample
sinks, the density is greater than the solvent. To determine the density ranges
for the plastics the following concepts may be useful. Think of the behavior and
densities of water, a rock, and a piece of wood. The density of water is 1.0
g/ml, the rock sinks so its density is greater than 1 g/ml, the wood floats so its
density is less than 1 g/ml.
If the above three solutions are very carefully layered, the salt solution is on the
bottom, the water is in the middle, and the alcohol floats on top. To help
determine, the density ranges, list the plastics in the proper places on the
diagram. The plastics that float on alcohol are less than 0.94 g/ml. Click the
online example for help
QUES. 10: Density Column
Solvent Density
Plastic abbrev. and recycle number
Floats on rubbing alcohol
---0.94 g/ml rubbing alcohol--sinks in alcohol, but floats on water
example from Help:
# 2 - HDPE = dens. range 1.0-0.94
---1.0 g/ml water--sinks in water, but floats on salt water
---1.2 g/ml sat. salt water--sinks in salt water
PHYSICAL AND CHEMICAL PROPERTIES OF PLASTICS
Ques. 11-13 (4points)
****At home collection of lab data ****
First make a descriptive list of the pieces of plastic including recycle numbers,
if known. Try to have an example of each recycle number or type of plastic. (If
you can not find one recycle number, that will be OK.) Bottom line you need 5
or 6 different plastic plus the two types of "packing peanuts".
Then carry out the classification tests (4-6) below and record the results as
follows separated by spaces and commas:
QUES. 11: DATA Property Listing:
Recycle No., Abbreviation, Chemical Name, product name(example - milk
jug), transmission of light, flexibility, solubility in water, solubility in
acetone.
4. Transmission of Light:
Classify the plastic samples according to transparent, opaque, or translucent.
5. Flexibility:
How easily does the sample bend? Does it have fine lines after bending called
"crazing" after it is bent? List the properties as: Rigid, brittle; Stiff but will
bend; Flexible or "crazes"
6. Solubility in Solvents:
Materials may be soluble in a particular solvent depending upon the nature of
the interaction of the molecules in the solid state. A general rule that is
followed is that: "Likes dissolve Likes". This means that substances which have
a similar property such as polarity will dissolve in each other. Some familiar
examples include salt (ionic) and sugar (polar) which dissolve in water (polar).
On the other hand oil (nonpolar) does not dissolve in water (polar). Oil based
paint (nonpolar) dissolves in turpentine (nonpolar). Finger nail polish
(nonpolar) dissolves in acetone (nonpolar). Some substances are not soluble in
anything due to the structure of the solid (this will include many of the
plastics).
Most plastics are insoluble in water and insoluble in acetone.
Two types of packing "popcorn" are found in the lab equipment baggie (Sshape vs. C-shape. Conduct the following solubility tests ONLY on those.
Set up two porcelain or glass cups. Put about 1/2 cup of water in one and 1/8 to
1/4 cup of acetone or finger nail polish remover in the second. Test the
solubility of each of the packing "popcorn" samples in acetone and water. Stir
around and wait about 2-3 minutes to see if anything is going to happen, as
these may prove to be the most interesting. These samples were provided in the
"baggie". For some fun try a styrofoam coffee cup with acetone. One of the
packing "popcorns" is starch based and eventually will dissolve at least
partially in the water but not the acetone.
QUES. 12: Use the textbook to find the monomer or partial polymer chemical
structures for at least three of the polymers listed above. At least give a word
description of the monomers present in the polymers and some of the more
important atoms.
QUES. 13: Why can plastics not be recycled or reused as one large group of all
plastics such as glass or paper or aluminum cans? Or stated another way, why
must plastics be separated by recycle numbers before they can be recycled? Be
specific and incorporate something from question 12 in your answer.
SUMMARY ACTIVITY:
QUES. 14: (2 points)
Recycling Scenario: Form a plan to separate and recycle as many of the
plastics as possible. Start with a mixed batch of household plastic items that
might be present in the recycling bin for garbage pickup. The recyclables are
transported to a large recycling center. How are you going to separate all of the
different types of plastics after they arrive at the recycle center and are all
mixed up?
Remember that you have paper labels, possible metal rings on some bottles,
plastic caps, and aspirator assemblies.
Other items to keep in mind are that you will need to wash or clean the plastic,
probably crush or break it into pieces, some hand inspection or sorting is also
currently used. Although not previously considered, blowing air might be a
way to separate some items. Can you separate some of the plastics by the
solubility or density properties as found in this lab exercise?
For full credit, your plan must include an application of some of the concepts
and principles of this lab - mostly density. Be specific about the recycle
numbers and/or types of plastic that float, sink, or dissolve at various stages of
the operation.