(Woman) :
We’ve been considering various useful hydrocarbon compounds, and today, we’re going to look at one of the most useful of all of these. That’s right, I’m talking about coal. There probably wouldn’t have been an Industrial Revolution in the eighteenth century without coal. Even today life would be very different if we didn’t have coal. So, where does coal come from? Well, imagine what the earth was like say, 300 million years ago—during the Carboniferous period. Much of the land was covered with luxuriant vegetation, especially ferns—ferns big as trees. Eventually, these plants died and were submerged in the waters of swamps, where they gradually decomposed. And we’ve seen what happens when plants decompose—the vegetable matter loses oxygen and hydrogen atoms, leaving a deposit with a high percentage of carbon. In this way, peat bogs were formed. Then, as time went on, layers of sand and mud are settled from the water over the peat bogs. These deposits grew thicker and thicker, and the pressure increased, and the deposits were compressed and hardened. And so you have—coal! All grades of coal have uses. Lignite, the lowest grade of coal, is often burned in furnaces for heat. Most bituminous coal, which has higher carbon content, is used by utility companies to produce electricity. Anthracite, which has the highest carbon content, is often distilled to produce coke. Coke is almost pure carbon and is used in the manufacture of steel. And coal tar, one of the by-products of producing coke, is used to make many different types of plastic.
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