Worlds of David Darling > Children's
Encyclopedia of Science > From Glasses to Gases > Chapter 6
FROM GLASSES TO GASES:
The Science of Matter
a book in the eXperiment! series by David Darling
6. New Materials, New Properties
More new substances are
being developed today than ever before. With the help of computers, scientists
can now see what materials might be like even before they actually make
them. They can design molecules that have specific properties. Then, they
can build these molecules, atom by atom, in the laboratory.
Often, important new materials are made by putting together other substances
that have useful properties. Plastics combine with nylon, for example, are
stronger. A mixture of two or materials is called a COMPOSITE. One of the
most widely used composites is carbon-fiber-reinforced plastic (CFRP), made
by embedding tough carbon fibers in a type of plastic known as epoxy resin.
Because it is strong and light, CFRP has proved to be an ideal material
for high-performance sports equipment, artificial limbs, and aircraft parts.
The amazing variety of new substances currently being created and tested
in laboratories around the world will have a huge effect on people's lives
in the future. But not every discovery finds a practical use. Sometimes
a material is found that has fantastic properties, but no one knows what
to do with it.
Crazy, Mixed-Up Matter
You will need:
What to do:
Roll the Silly Putty into a ball and drop it on a hard floor. What
happens? Compare how well it bounces with the balls you used in the
"Bouncing Back" experiment.
Pull the Silly Putty apart slowly. How does it behave? Pull it apart
quickly. Is there and difference? Experiment pulling the substance
apart at various rates. Can you find a point at which its behavior
Roll the Silly Putty into a ball again, place it on a hard floor,
and strike it sharply with a hammer. What happens?
Taking it further:
Try these tests again after placing the Silly Putty in the freezer
for 15 to 30 minutes. Try them again after the Silly Putty has been
warmed on a radiator for a few minutes. Invent your own experiments
to find out more about Silly Putty's strange properties.
Silly Putty was discovered accidentally by scientists who were trying
to develop other substances, such as silicone rubber, resins, oils,
and greases. This is a good example of the fact that science rarely
moves ahead in well-planned steps. Often, researchers have only a
vague idea of where their research may lead. The trick is to be able
to recognize when something new and potentially important turns up.
Silly Putty was certainly new – and very strange – but
it has never been used for anything important. For several years after
its discovery, its only practical use was as a kneading material to
help strengthen hands that were crippled. Then a big rubber company
began using it as the core material for its golf balls. Silly Putty
rebounds higher and faster than natural rubber, so the new center
allowed the balls to be driven further.
It is as a toy, however, that Silly Putty has made its name. Its strange
properties come from the fact that this freak form of silicone is
really a slow-moving liquid. Its molecules simply can't flow past
one another above a certain speed. If you pull or hit Silly Putty
hard, the molecules snap apart. On the other hand, if you pull gently,
the molecules easily slide over one another. In between these two
extremes, Silly Putty molecules display a springiness that allows
them to bounce back if they are thrown against a wall or hard floor.
Along with new types of metals, plastics, and composites, a lot of work
is being done to develop new ceramics. A ceramic material is basically a
piece of clay that has been heated, or fired, to a high enough temperature
to make it permanently hard. People have been making clay pots for over
10,000 years, and today almost every home contains a range of ceramic materials
– in the form of bricks, tiles, and china plates.
The most important property of a ceramic is its ability to withstand heat.
Until recently the problem has been that ceramics were very brittle. A kitchen
tile, for instance, will shatter if dropped and will crack if its temperature
changes too quickly. The new ceramics are harder, stronger, more heat-resistant,
and better able to stand up to sudden temperature changes than ordinary
Among the new materials are the aluminum-oxide ceramics used to make the
insulators of engine spark plugs and the heatshields of spacecraft. These
can survive temperatures of up to 3,800°F (2,073°C). In the future,
ceramics will play an increasingly important part in our everyday lives.
Metal car engines may soon become a thing of the past. Metal is heavy and
it cannot stand up to the high temperatures at which future engines will
run. Already some car engines run three times hotter than they did a decade
ago, enabling them to use less fuel and cause less pollution. Instead of
steel and aluminum, their high-temperature parts are made of advanced ceramics.
Other new materials will form the outer parts of future cars. The body may
be made of tough composites that are as strong as steel but lighter in weight.
Another possibility is the use of "smart" materials that can sense when
they have been damaged and then heal themselves like human skin.
You will need:
- A collection of materials, including candy wrappers, a sheet
of newspapers, a paper tissue, a piece of cardboard, a plastic
garbage bag, an apple core, an empty can, a plastic bottle, fast-food
containers, old plastic toys, pieces of different metals, an old
bicycle inner tube, and any other waste items you wish to test
- Sticks, for use as markers
- A permanent marker pen
- A spade
- A spare patch of ground
- A set of scales
What to do:
Cut the materials (except those made of metal and hard plastic) into
pieces of roughly the same size. Choose a patch of ground, in your
yard or at school, that will not be disturbed. Ask permission first.
Dig a hole 1 foot deep and place one of the materials in it. Fill
in the hole and press down the soil. Push a stick in above the material
and label it with the marker pen. Bury and label each of the other
materials in an orderly arrangement nearby. After one month dig up
the materials and see whether or not they have changed. Record your
Taking it further:
This experiment could be continued over a longer period of time to
study the gradual decay of the buried substances. Which materials
do not seem to change at all? In what type of ground do materials
decay fastest and at what time of year?
Back to Nature
Substances that break up in the ground and disappear harmlessly are called
BIODEGRADABLE. One big problem today is that much of the waste that we throw
out in huge amounts does not decay when it is buried.
Plastic waste is especially hard to deal with. It can survive in the ground
almost unaffected for many years. Because of this, researchers are now developing
new types of plastics that will quickly break down. Some of these new plastics
are turned to powder by exposure to sunlight. Others can be eaten by microbes
in the soil.
The latest type of polythene carrier bag looks and feels a bit unusual.
This is because it has starch molecules mixed in with the long chains of
polythene molecules. When the bag is buried in the ground, the starch is
eaten by bacteria in the soil. The rest of the plastic bag then falls apart
so that little of it remains after about 18 months.