Question: Read "A Glance at Glass" by Lance Carson paying particular attention to the third paragraph. Given your understanding of the main idea of the passage, write a few sentences that describe the purpose and how it functions in the passage as a whole.

Story:

You probably see or use this material every day, and it's also been used by ancient craftspeople, famous artists, and cutting-edge modern scientists. It can be found in amazing technological inventions and in humdrum household objects. It can be solid or liquid, clear or colorful, and it can help people see, stay safe, and communicate. It is made mostly of sand but it can be blown up like a bubble or stretched for miles. This material is glass and it's truly one of the world's most remarkable and adaptable materials. "Glass is really an unsung hero of modern life," said Kerry Morelli, a tour guide at the Keller County Glass Factory. "We overlook it often—sometimes we literally look right through it!—but without glass our lives would not be the same at all." Morelli begins each tour by describing some of the many common uses of glass: windows, windshields, bottles, mirrors, television and computer screens, drinking glasses, eyeglasses, and even fiber-optic cables for computer communication. She often asks factory visitors to try to remember how many times they saw or used glass that day. The number is generally too high to even remember! The glass factory has a small museum that showcases the history of the material. "On display are some small glass beads manufactured in ancient Egypt," said Morelli. "They don't look special, just circles or cylinders of colorful glass, but they represent some of the earliest glassmaking technology known in history." Near the Egyptian beads in the display are two very rare examples of ancient Roman blown glass. The Romans discovered that artisans could use metal rods to blow air into blobs of melted glass. This technique of glass blowing could produce beautiful bottles, vases, pitchers, and jars. The discussion of early glassmaking prepares visitors for their trip into the glass factory itself. They can watch skilled workers producing glass and then turning the molten material into a wide array of attractive creations. Morelli narrates each step in the process. Many visitors are surprised to learn that glass is actually made of silica, a kind of sand, mixed with two other powdery ingredients known as lime and soda. "We turn this rough, gritty sand and powder into smooth, clear glass," said Morelli. "The trick is in heating it to extreme temperatures. If you think the sand at the beach is hot on your feet, you wouldn't like this hot sand at all! We raise the sand mixture to more than 1,500 degrees Fahrenheit to turn it into molten glass. That's hot enough to melt most kinds of metal." Sidebar: Natural Glass Not all glass is manufactured in factories. Some rare varieties of glass are actually made in nature. The heat of a volcano, for instance, can melt sand and other materials into a glasslike form. One volcano-made glass is the shiny, sharp, black obsidian. Sometimes the heat and impact of meteorites striking the earth can even cause glass to form!

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