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U5_Exam1-S10-INFO

U5_Exam1-S10-INFO - glass and ceramics Silicon carbide(SiC...

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Chemistry 152 Spring 2010- Exam 1 Information Sheet Dr. Pollard Silicon is the second most abundant element in the Earth's crust, after oxygen. However, it does not exist in pure form on our planet. Most rock consists of compounds of silicon, and sand consists largely of silica, or silicon dioxide (SiO 2 ). Silicon is a semiconductor material of enormous significance in the electronics industry. Most importantly, it permitted the invention of the transistor in 1947, which replaced the vacuum tube and thereby made possible electronic devices that are smaller by orders of magnitude and consume much less power. The silicon wafers used in electronic chips and photovoltaic cells are sliced from single crystals of pure silicon, grown artificially in cylindrical form. These cylindrical crystals can now be grown up to four feet long, with a diameter up to five inches, and an impurity content of less than a few parts per hundred billion. Compounds of silicon have other important uses. They are used in the production of metal alloys. Silica is the principal ingredient in
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Unformatted text preview: glass and ceramics. Silicon carbide (SiC) is used as an industrial abrasive. Quartz crystals vibrate at a constant resonant frequency when excited, and so they are used as timing devices in everything from wristwatches to radios. Silicon polymers, or silicones, are used to make caulk, electrical insulation, hydraulic fluids, anti-foaming agents, water-repellent coatings for fabrics, cosmetic implants, and many other goods. Motorcycle mechanics use silicone grease in applications that see high temperatures, for example on the backs of brake pads. Unlike petroleum-based greases, silicone grease does not liquefy and run away when heated. The central goal of this assessment is that you demonstrate that you can apply chemical thinking to explain and make predictions about the chemical reactivity of silicon and silicon compounds of central importance in modern society....
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