Look through the text
and complete the gaps.Materials That Changed History
Where would
we be without wood, ceramics, glass, iron? Here, look at 10 materials that were
very important for humanity, ranging from the most ancient ones to the 21st
century.
пустоFIBER & CLOTH
Before
stone there was wood. We humans are, after all, products of the forests. Our
material world was once one of logs, sticks, bamboo, and many other forms that
wood takes in nature.
Wood
allowed humans to transform rivers and seas from barriers to highways; to build
fences, homes, and walls, even when little stone was available; and to furnish
their lives with everything from beds and chairs to buckets and barrels. In the
last century wood extended to new forms, including slices, laminates,
particles, and chips.
пустоCERAMICS
In the 21st
century, we don’t think much about pots made from fired clay. But back in the
times, ceramics was one of indicators of a society's development. An
"aceramic" society had few ways of storing food or water, and thus
its agriculture was limited and primitive.
Clay can be
shaped and then hardened by drying, but only when it is baked to high
temperatures, it can keep its shape over a range of conditions. Combining clays
with other minerals and then firing the mixture resulted in brilliant colors.
пустоPLASTICS & RUBBER
While a
limited number of "fibers" exist in nature, there is no cloth. And
the fibers that do exist—silk, cotton, or wool, for example—have to be transformed
before they can be made into cloth. How humans learned to take the hair of a
sheep or goat and twist hundreds or thousands of individual hairs together to
make wools is one of the great mysteries of our early history.
The variety
of cloth has not stopped the application of modern chemistry. While some of the
earlier efforts at fashioning clothing from synthetic materials such as
polyester became jokes, today it is a rare wardrobe that does not feature some
cloth whose history began in a test tube rather than on a farm.
пустоWOOD
The first
metal that humans could make use of was copper. But bronze, an alloy of copper
with small amounts of tin, is a much more useful form.
As the
first alloy, bronze started the use of metals, mainly for weapons. The first
swords had bronze blades with sharp edges.
пустоIRON & STEEL
Even in the
21st century, no more important metal exists than iron, and this has been true
for as much as 3,000 years. Workable ores of iron are in almost every part of
the world, and different techniques can produce forms of the metal with a great
range of properties.
For the
last century and half, the most important form of iron has been steel. Steel is
actually a great range of materials, whose properties depend both on the amount
of carbon contained—typically between 0.5 and 2 percent—and on other alloying
materials.
пустоPAPER
The first
glass was probably made by accident, as sand found its way into an oven and
then melted. While we think of glass as normally clear, it took centuries of
experience and experiment to produce a clear glass.
Glass is
made by heating sand with a "flux," which is a mineral that will
lower the melting point of the mixture.
пустоBRONZE
Humans tried
to write for thousands of years before they had paper—writing can be put onto
stone, clay, wood, cloth, skin, and other surfaces. But even with so many
alternatives and electronic media, a world without paper would be very
different.
Paper is
one of a number of inventions that came out in China about 2,000 years ago.
пустоGLASS
For
thousands of years, people liked a small number of materials distinguished by
their appearance: ivory, tortoiseshell, and horn were luxury items. In the
1800s, the growth of markets and understanding of chemistry made it possible to
produce such items in great quantities at low cost. The first commercial
plastic was celluloid, made from nitrated cotton and camphor. When this
combination was heated under pressure, it was made into everything from combs
to dolls and ping pong balls.
Closely
related to plastics was rubber, which started out as a natural product brought
to Europe from South America. The Europeans adapted the production techniques.