Suppose you could step inside a time machine and go back 60 or 100 years. You may easily convince yourself a day without cars, telephones, and television—maybe even computers—might be kind of fun. Have you thought about the little things, though? Little things are often what are missed the most.

Imagine a day without touching something made of plastic!

People were cleaning their teeth before there was a choice of red, blue or purple plastic toothbrushes, but would you really want one made from metal or wood? Milk and shampoo used to be sold in glass bottles, and that wasn’t a problem unless you dropped one and it broke. What a mess!

The word plastic comes from the Greek word plastikos, meaning "able to be molded." That characteristic, or what scientists call "property," makes plastic perfect for things like action figures and dolls. What other properties does plastic have that make it a good choice for particular products? Try these experiments, then use what you learn to list 10 or even 20 good candidates for plastic.

Materials

• pieces of aluminum, plastic, and wood about the same size (approximately 2’ long, 1" wide, and 1/8" thick (rulers or yardsticks might work)
• two 6" stacks of books
• a 2-pound canned good item
• a 4-foot length of string
• a tennis ball
• a plastic and a paper grocery sack.

Place the two stacks of books about 9" apart. Lay the aluminum strip across the books, making a level bridge. Lay the string parallel to the strip. Next place the canned good in the middle of the strip. Use the string to measure the deflection (bend) in the strip and write down your observation.

Repeat the process with the wood and plastic, then discuss what you have observed about the strength and stiffness of each material. (Which material would you choose for a toothbrush handle? How about the toothbrush bristles?)

Next, soak the tennis ball in water until it is thoroughly wet. Place it first in the plastic sack and then the paper one, letting it sit in each for 5 minutes before shaking each bag vigorously. Which bag stays dry? Does the water cause the paper bag to sag and even break? What can you conclude about how each material repels or absorbs water? Which bag would you choose to carry your carton of ice cream?

The information, or data, you’ve gathered from your experiments is just what a scientist uses to decide what material to use in an engineering design!