Temperature
Three scales of temperature, each of which permits a precise measurement, are in concurrent use: the Fahrenheit,Celsius, and Kelvin scales. These three different temperature scales were each developed by different people and have come to be used in different situations.
The scale that is most widely used by the general public in the United States is the Fahrenheit scale. In 1714,Daniel Gabriel Fahrenheit, a German physicist who was living in Holland and operating an instrument business, developed a mercury-in-glass thermometer and the temperature scale that still carries his name. His original scale had two fixed points: 0° was the lowest temperature that he could achieve in a solution of ice, water, and salt, and 96° was what he believed was the normal temperature of the human body (though this was later determined to be 98.6°).Based on this scale, he calculated that the freezing point (or ice point) of water was 32°; in later studies, it was determined that the boiling point of water (the steam point) was 212°. The Fahrenheit scale came to be accepted as the standard measure of temperature in a number of countries, including GreatBritain, and from there it was spread toBritish colonies throughout the worlD、Today, however, the United States is the only major country in the world that still uses the Fahrenheit scale.
The scale that is in use in many other countries is theCelsius scale.AndersCelsius (1701-1744), a Swedish astronomer, developed a thermometer in 1741 that based temperatures on the freezing and boiling temperatures of water. On the thermometer thatCelsius developed, however, 0° was used to indicate the boiling temperature of water, and 100° was used to indicate the freezing temperature of water.After his death, the scale was reversed by a friend, the biologistCarl yon Linne(1707-1748), who achieved acclaim for his development of the Linnean classification system for plants and animals. On the new scale after the reversal by yon Linne, 0° indicated the freezing temperature of water, and 100° indicated the boiling temperature of water.
At around the same time thatCelsius and yon Linne were working on their thermometer in Sweden, a similar thermometer was being developed in France.
After the French Revolution, the scale developed in France was adopted as part of the metric system in that country under the name centigrade, which means "a hundred units" and from there it spread worldwide.
In 1948, an international agreement was made to rename the centigrade scale theCelsius scale in honor of the scientist who was first known to use a 100-degree scale, though it should be remembered that the scale thatCelsius actually used himself was the reverse of today’s scale.

A、third scale, the Kelvin scale, is generally used today for scientific purposes. This scale was first suggested in 1854 by twoEnglish physicists: William Thomson, Lord Kelvin (1824-1907) and James Prescott Joule (1818-1889). The Kelvin scale defines 0° as absolute zero, the hypothetical temperature at which all atomic and molecular motion theoretically stops, and 100~ separates the freezing point and boiling point of water, just as it does on theCelsius scale. On the Kelvin scale, with 0° equal to absolute zero, water freezes at 273°, and water boils at a temperature 100° higher. The Kelvin scale is well suited to some areas scientific study because it does not have any negative values, yet it still maintains the 100° difference between the freezing point and boiling point of water that theCelsius scale has and can thus easily be

Air Pollution andAcid Rain
The increasing variety and prevalence of pollution presents the world with many extremely daunting problems, air pollution in particular ranks among the most serious. In the following text, air pollution and acid rain caused by automobiles will be discusseD、Certain solutions to the problem will be provided in the conclusion.
It is widely known that cars are the main cause of air pollution in cities, accounting for 60% to 90% of all air pollution. This will get worse as the number of cars increases in urban areas. How do cars cause air pollution First we must examine how a car works. There’s a mixture of petrol in the car’s internal combustion engine which create the force for the automobile to move. Unfortunately, in this process there are some poisonous chemicals which remain; these poisonous chemicals mainly come out of the car through the exhaust, it’s not just what comes out of the car exhaust that is dangerous, the brake system also causes pollution.Brakes on cars release asbestos, it is a highly dangerous substance and it can kill humans.Also, the tires themselves give off small rubber particles which are not very healthy.
Acid rain caused by air pollution has strongly influenced people’s lives. It is almost impossible to describe the mathematical relationship between what goes up as pollutant emissions and what comes down as acid rain. However, we do know the primary source of acid rain is the pollution released by power plants. The pollutants combine with moisture in the atmosphere and then fall as an acid rain. Germans often call it royal water, because it can break down golD、
The royal water falls in the form of rain or snow on the GermanBlack Forest and attacks the soil. Microorganisms within the soil perish and metals harmful to trees like aluminum leak into the grounD、At the same time, the acid rain attacks the trees’ leaves and dissolves their waxy coating. The leaves then shrivel and die.About one in every ten trees in theBlack Forest is a fir. 76% of all firs in theBlack Forest are dying. 41% of all spruce are diseased, 43% of all pine are diseased, 26% of beech trees and 16% of all other trees are dying.Environmental groups like Green Peace campaign aroundEurope trying to stop the causes of acid rain.
We need to find solutions to this problem. First, we should try and discourage the overuse of cars. We could do this by raising taxes on petrol or by making cars more expensive.
Second, we can encourage alternative methods of transportation. For example, in Shanghai recently, a subway has been built underground, which takes some of the pressure off the roads. Some people would rather use the underground than drive their cars. Next, we could develop and use cleaner fuels instead of petrol. For example, we might use natural gas in the future or we might experiment with battery powered cars.
Finally, the actual by-products of vehicle emissions must be manageD、
A、[■] Scientists and engineers are now trying to use mechanical means for reducing the amount of chemicals that are emitted from cars’ exhaust pipes.
B、[■] Germany is now leading the way in attacking this part of the problem.
C、[■] In order to clean up motor vehicle emissions, all new cars in Germany must now meet new emission standards and be fitted with a device called a catalytic converter.
D、[■] This is a device that is fixed over the exhaust and controls the carbon monoxide and other dangerous chemicals that cars give off. Like Germany, the United States also introduced strict clean air-controls on motor vehicle emissions in the mid-70s as part of their efforts to reduce acid rain. It’s unlikely that any one of these solutions will work on its own. It will take a combination of all four of these solutions to help solve the air pollution problem. Look at the four squares

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