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1.2: Chemicals Compose Ordinary Things

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    53685
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    Before humans had any understanding of chemistry, they used whatever they could find in the world around them. One type of material that was easily accessible to early civilizations, at least in small amounts, was metal. Native gold, silver, and copper, and compounds of tin and iron can all be found occurring naturally in cliffs and caves (in fact, the discovery of natural gold in El Dorado County, California is what lead to the great Gold Rush of 1849) and, as a result, these metals became very important to people in early times.

    Many ancient civilizations fashioned tools, jewelry, and weapons out of metal that they scavenged from rocks around them. After a while, however, people discovered that by mixing naturally occurring metals with other substances, they could create new materials that often had superior properties.

    375px-Assorted_bronze_castings.JPG

    Figure \(\PageIndex{1}\): Bronze castings.Image used with permission (public domain)

    Some of the oldest materials produced by man include mixtures (or more specifically solutions) of metals known as alloys. One of the earliest alloys ever discovered was bronze. Bronze can be made by heating chunks of tin and copper until they are liquid and then mixing the two pure metals together. Bronze was very important to early civilizations because it was more resistant to rust than iron, harder than copper, and could hold an edge and be sharpened to create tools and weapons.

    Another alloy, produced early in the history of civilization, is steel. As you learned in an earlier section, steel is an alloy of iron and carbon (or charcoal). Steel, particularly Wootz steel (which required a special technique that involved the addition of glass), was especially strong, and could be fashioned into very sharp edges, perfect for swords. Another old material whose production was known to early civilizations is brass. Again, brass is an alloy, made of two pure metals, copper, and zinc. Early Romans knew that if they melted copper, and a zinc ore known as calamine together, they could produce brass, which was both shiny like gold, and resistant to rust. Brass was a common material used to make coins.

    What you might notice about these "old" materials is that they are mainly alloys. At the time when bronze and brass and steel were discovered, people didn’t know much about the composition of matter or about how matter was assembled on a microscopic scale. As a result, inventing materials was largely a matter of trial and error. Towards the end of the 19th century, however, scientists were beginning to understand the make-up of matter, and this understanding led to new insight into how to develop materials with desirable properties.

    One of the huge breakthroughs in recent history has been the discovery of plastic and plastic products. Initially, plastic was made by chemically modifying cellulose, a naturally occurring chemical found in plants. As chemical knowledge developed, however, scientists began to realize that plastics had special properties because, on a microscopic scale, they were composed of thousands of tiny chains of molecules all tangled up together. Scientists reasoned that if they altered the chemicals in these chains, but still managed to keep the chains intact, they could make new plastics with new properties. Thus began the plastic revolution!

    Plastic_household_items.jpg

    Figure \(\PageIndex{2}\): Various household products made of plastic. Image used with permission (CC-SA-BY-3.0; ImGz)

    Semiconductors are another class of "new" materials whose development is largely based on our improved understanding of chemistry. Because scientists know how matter is put together, they can predict how to fine-tune the chemical composition of a semiconductor in order to make it absorb light and act as a solar cell or emit light and act as a light source. We've come a long way from our early days of producing bronze and steel. Nevertheless, as our understanding of chemistry improves, we will be able to create even more useful materials than we have today.

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    1.2: Chemicals Compose Ordinary Things is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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