6.21

Your metropolitan area has been warned by the EPA to lower sulfur dioxide and nitrogen oxide emissions or it will lose substantial federal funding. One citizen's group calls for conservation as a means of drastically reducing electricity consumption. A second group advocates curtailing the use of automobiles through a variety of means. Choose either of these or some other position to support. Research the position and present your findings by writing a couple paragraphs.

9.6

Gather up a variety of plastic items from your residence - plastic bags, soda bottles, whatever happens to be at hand. Make a list of the objects and note the properties of the plastics. Include color, transparency, flexibility, elasticity, hardness, and other properties that could be used to classify and identify plastics. Try to draw conclusions about which objects are made from the same material.

9.7

For each of these uses, specify the desirable properties of plastic and suggest the most suitable polymer or polymers.

a. a bread bag
b. a soft-drink bottle
c. "bubble" packaging around a toy
d. bottle caps
e. outdoor lawn furniture
f. a drinking water bottle

9.31

Plastics vary in density. When placed in a liquid, a substance, such as plastic, floats if its density is less than that of the liquid, and the substance sinks if it is more dense than the liquid.

The densities (g/mL) of four common are: high-density polyethylene 0.95-0.97; polyethylene terephthalate 1.38-1.39; polypropylene 0.90-0.91; and polyvinyl chloride 1.18-1.65. The six liquids and their densities are:

Liquid Density (g/mL)

Methanol 0.79

An ethanol/water mixture 0.92

A different ethanol/water mixture 0.94
Water 1.0

Saturated Solution of MgC1 1.34
2

Saturated Solution of ZnC1 2.01
2

Using the densities of liquid and of the plastics given, develop a procedure by which the individual plastics can be separated from a mixture containing pieces of all four plastics.