Questions 1 and 2 refer to the following information.
Teflon is a synthetic substance called a polymer. This polymer is a chain of thousands of small molecules of carbon and fluorine atoms. Teflon is used in the manufacturing of many items, including medical devices and cookware. It is useful because nothing will stick to it. This property of being non-sticky is the result of bonding the fluorine atoms to the carbon atoms. Once fluorine is combined with the carbon, the molecule becomes so inert and stable that nothing else will react with it. Teflon will not burn, no bacteria or fungi can grow on it, no acid will dissolve it, and it does not melt until the temperature reaches 620°F. It is so slippery that large sheets of Teflon have been used to make artificial ice-skating rinks.
During the process of making Teflon, chemists can alter the polymer by adding other chemicals. This gives the polymer new properties. For example, some Teflon is made that has one inert end and one sticky end. When it is applied to fabrics, it forms a protective coating because the sticky end binds to the cloth and the inert end prevents water, dirt, or oil from reacting with the material.
Questions 4 and 5 refer to the following information.
Errors in weather prediction occur for three main reasons. Weather forecasters do not yet understand all the physical interactions that occur when different portions of the atmosphere mix together. More problems occur because of lack of data. For example, there are large areas of North America where weather information is not collected. Incomplete information results in error because a slight weather change in one location can drastically affect the conditions in a nearby area. For the last forty years weather satellites have helped solve this problem, but even they do not cover the entire earth.
Surprisingly, computers used in forecasting weather also result in errors. Although the computers actually do their job very well, the necessary calculations are so complex and take so long that shortcuts must be used. These shortcuts are simplified programs that allow the calculations to be done more quickly, but the results seldom give a complete picture of the weather.
Despite these problems, most weather predictions are still useful. Weather forecasters can predict the temperature, wind direction, and speed fairly accurately. Weather predictions made one or two days ahead are usually accurate. Beyond seventy-two hours, though, they can be depended on only for general weather patterns.
Questions 6 through 8 refer to the following information.
The world appears to have enough low-cost light oil at the present time. However, these supplies will eventually be depleted. When this occurs, countries will have to recover their vast resources of heavy oil and bitumen from the earth and refine them into usable light oil. Bitumen is a very heavy, sticky oil that contains much sulfur. In North America, the Canadian province of Alberta contains the largest concentration of heavy oil and bitumen, which is found mainly in oil sands. How heavy oil and bitumen are recovered depends on how deeply they are buried.
Ten percent of the bitumen is close enough to the surface to be mined from open-pit mines. After the oil is removed, the sand is returned to the pit. Currently, 15 percent of Canada’s oil is produced from bitumen by open-pit mining.
Deeply buried deposits of bitumen make up about 90 percent of Canada’s heavy oil resources. However, it is very difficult to get this bitumen because it is so thick and sticky that it is almost a solid. The technology to recover it involves heating the bitumen deep in the ground and pumping it to the surface through wells before it cools. The process is somewhat like recovering light oil, except that light oil is easy to reach because it occurs naturally as a liquid in porous rocks beneath the ground.
The production of refined oil from bitumen and heavy oil is an expensive process and one that does not pay for itself at the current low price of conventional light oil. Alberta is working on the problem so that when the world’s reserves of light oil run out in the future, Alberta will be ready to produce synthetic light crude oil from its vast bitumen resources.
Questions 9 and 10 refer to the following information.
High tide occurs on Earth when the gravitational pull of the Moon causes a tidal bulge. The Moon’s gravitational pull raises millions of tons of water, which wash far inland across ocean shores. Large ships have taken advantage of tides for years to move in and out of harbors. But so far people have used tidal energy only occasionally to provide energy on land. Now scientists are taking a closer look at the power of tides.
Falling water has energy. As high tides recede, large amounts of water fall. Scientists think this action could generate power in several ways. For example, dams might trap high tides as they rise. Then, when the tide falls, the water could be channeled through turbines to generate electricity. Another proposed method would resemble the waterwheels people of earlier centuries used on many rivers. The tides could turn reversible paddlewheels when they came in, and then again when they went out.
Scientists predict that tidal energy will be clean and leave behind no waste products. They are still studying the effects tidal dams might have on ecology.