单项选择

When the temperature of a liquid is raised enough, the liquid boils. This means that bubbles of vapor, containing millions of molecules, form below the surface. In order for such bubbles to be produced, the pressure of the vapor inside them must be equal to the pressure of the air upon the surface of the liquid. If the air pressure is greater, the bubble will collapse. The boiling point of a liquid, then, is the temperature at which the vapor pressure of the liquid is equal to the atmospheric pressure upon the liquid at the surface.
The pressure of the atmosphere at sea level is about one kilogram per square centimeter. We call this pressure one atmosphere. The boiling point of a liquid, therefore, is the temperature at which its vapor pressure equals one atmosphere. The boiling point of water is 100 Celsius; of ethyl alcohol 78.5 Celsius; of mercury, 356.9 Celsius.
If the pressure on the surface of the water is reduced, the boiling point will be lower. Now the higher up we go from sea level, the lower the atmospheric pressure becomes, since there is less air to press upon us. Hence, while water boils at sea level at a temperature of 100 Celsius, its boiling point on a mountain three kilometers high is only 90 Celsius. Since the temperature of water does not rise as a result of boiling, it would take you longer to cook potatoes or carrots in boiling water on the mountain than it would at sea level.

Which statement of the following is correct according to this passage（）

A:The boiling point of a liquid is the original temperature. B:The higher the pressure on the surface of the liquid, the quicker the boiling point will be reached. C:The boiling point of a liquid is 100 Celsius. D:Both Ｂ and Ｃ.

When the temperature of a liquid is raised enough, the liquid boils. This means that bubbles of vapor, containing millions of molecules, form below the surface. In order for such bubbles to be produced, the pressure of the vapor inside them must be equal to the pressure of the air upon the surface of the liquid. If the air pressure is greater, the bubble will collapse. The boiling point of a liquid, then, is the temperature at which the vapor pressure of the liquid is equal to the atmospheric pressure upon the liquid at the surface.
The pressure of the atmosphere at sea level is about one kilogram per square centimeter. We call this pressure one atmosphere. The boiling point of a liquid, therefore, is the temperature at which its vapor pressure equals one atmosphere. The boiling point of water is 100 Celsius; of ethyl alcohol 78.5 Celsius; of mercury, 356.9 Celsius.
If the pressure on the surface of the water is reduced, the boiling point will be lower. Now the higher up we go from sea level, the lower the atmospheric pressure becomes, since there is less air to press upon us. Hence, while water boils at sea level at a temperature of 100 Celsius, its boiling point on a mountain three kilometers high is only 90 Celsius. Since the temperature of water does not rise as a result of boiling, it would take you longer to cook potatoes or carrots in boiling water on the mountain than it would at sea level.

Which statement of the following is false according to the passage（）

A:The boiling point of water on a mountain three kilometers high is only 90 Celsius. B:It would take you longer to cook potatoes in boiling water on the mountain than it would at sea level. C:When the temperature of a liquid is raised enough, the liquid boils. D:The boiling point of water on a mountain six kilometers high is 95 Celsius.

When the temperature of a liquid is raised enough, the liquid boils. This means that bubbles of vapor, containing millions of molecules, form below the surface. In order for such bubbles to be produced, the pressure of the vapor inside them must be equal to the pressure of the air upon the surface of the liquid. If the air pressure is greater, the bubble will collapse. The boiling point of a liquid, then, is the temperature at which the vapor pressure of the liquid is equal to the atmospheric pressure upon the liquid at the surface.
The pressure of the atmosphere at sea level is about one kilogram per square centimeter. We call this pressure one atmosphere. The boiling point of a liquid, therefore, is the temperature at which its vapor pressure equals one atmosphere. The boiling point of water is 100 Celsius; of ethyl alcohol 78.5 Celsius; of mercury, 356.9 Celsius.
If the pressure on the surface of the water is reduced, the boiling point will be lower. Now the higher up we go from sea level, the lower the atmospheric pressure becomes, since there is less air to press upon us. Hence, while water boils at sea level at a temperature of 100 Celsius, its boiling point on a mountain three kilometers high is only 90 Celsius. Since the temperature of water does not rise as a result of boiling, it would take you longer to cook potatoes or carrots in boiling water on the mountain than it would at sea level.

The liquid boils only when （）

A:the temperature is raised B:the bubbles of vapor form below the surface C:the temperature of the liquid is raised enough D:the temperature of the liquid is near 100 Celsius

The liquid boils only when ______.

A:the temperature is raised B:the bubbles of vapor form below the surface C:the temperature of the liquid is raised enough D:the temperature of the liquid is near 100 Celsius

If you made a list of all the jobs performed by the different kinds of energy, you would fill many pages.
Nuclear energy is used in some areas of the United States. But there are dangers. Waste materials from nuclear (51) would destroy life if they leaked (52) the land. When nuclear energy is produced, a lot of (53) is produced, too, so a flow of lake or ocean water is used to cool the operations. Then the water (54) to its source. If the returning water were too hot, it would destroy fish and other (55) .
Cow manure is being used to produce a kind of (56) . The manure from farms is put into a machine to convert it to a liquid. Then the gas is formed (57) a natural process. If the converter were not so (58) at the present time, it would be used in many places to provide (59) .
Garbage has become an energy source. It (60) to oil, steam, or electricity, or it is used on the land.
But recent (61) about power supplies has led to increased interest in the use of wind (62) a source of electrical power. Windmills are clean and they (63) no waste. And they use a (64) resource. Some scientists consider that wind energy systems can fulfill a valuable (65) in meeting the energy needs of industrialized nations and of the developing world.

A:gas B:liquid C:solid D:air

If you made a list of all the jobs performed by the different kinds of energy, you would fill many pages.
Nuclear energy is used in some areas of the United States. But there are dangers. Waste materials from nuclear (51) would destroy life if they leaked (52) the land. When nuclear energy is produced, a lot of (53) is produced, too, so a flow of lake or ocean water is used to cool the operations. Then the water (54) to its source. If the returning water were too hot, it would destroy fish and other (55) .
Cow manure is being used to produce a kind of (56) . The manure from farms is put into a machine to convert it to a liquid. Then the gas is formed (57) a natural process. If the converter were not so (58) at the present time, it would be used in many places to provide (59) .
Garbage has become an energy source. It (60) to oil, steam, or electricity, or it is used on the land.
But recent (61) about power supplies has led to increased interest in the use of wind (62) a source of electrical power. Windmills are clean and they (63) no waste. And they use a (64) resource. Some scientists consider that wind energy systems can fulfill a valuable (65) in meeting the energy needs of industrialized nations and of the developing world.

A:oil B:liquid C:power D:fuel


? ?阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。

{{B}}? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?The Discovery of Penicillin (青霉素){{/B}}
? ?In the autumn of 1928, a Scottish scientist Alexander Fleming was searching for a substance that would kill fatal germs(细菌). On his desk were small plates containing the germs. {{U}}?(51) ?{{/U}} evening, he forgot to cover one of the plates. When he arrived the next morning, he found a spot of green mould(霉菌)in one plate. This is not strange because the room was rather damp(潮湿) ,with {{U}}?(52) ?{{/U}} one window. But Fleming did not throw out the spoiled plate, be cause something unusual caught {{U}}?(53) ?{{/U}} attention.
? ?On the uncovered plate, near the green mould, the germs {{U}}?(54) ?{{/U}}. That meant that the mould had killed the germs there. Fleming watched the mould grow {{U}}?(55) ?{{/U}} several days. As the green mould spread, it killed more and {{U}}?(56) ?{{/U}} germs.
? ?Fleming began to study the mysterious mould. It grew and grew. Then he noticed tiny drops of liquid on the surface of the mould. Perhaps this was the chemical that was destroying the germs.
? ?Fleming drew off the liquid, drop by drop. He put this liquid in a test tube, and it {{U}}?(57) ?{{/U}} the germs in the tube. He called the {{U}}?(58) ?{{/U}} penicillin.
? ?Fleming published his finding in a British medical journal {{U}}?(59) ?{{/U}} 1929. But for ten years, while he continued to experiment with penicillin, his discovery was largely ignored near the medical world.
? ?Then in 1938 a team of British scientists happened to {{U}}?(60) ?{{/U}} about Fleming’s findings in an old medical journal. They made further {{U}}?(61) ?{{/U}} with the drug. They tested it on animals and then {{U}}?(62) ?{{/U}} human beings. In 1941, it was declared safe for use on humans. Soon penicillin was produced in large quantity and was used to {{U}}?(63) ?{{/U}} many infections(感染).
? ?Penicillin is a very powerful drug. {{U}}?(64) ?{{/U}} can treat many kinds of infections. However, it has some bad effects. Sometimes it causes a skin problem or a light fever. And it can be fatal for people {{U}}?(65) ?{{/U}} are allergic(过敏性的)to it. That is why before you take a penicillin shot, the doctor gives you a test shot first.

A:test B:liquid C:tube D:place

Volcanoes

There are thousands of volcanoes (火山) all over the world. What makes volcanoes What happens
The inside of the earth is very hot. Because it is very, very hot, the rock has melted like ice. It has become liquid, like water. It is always boiling, like water in a kettle. If you have seen a kettle boiling, you know that the steam and boiling water try to get out. The very hot melted rock inside the earth also tries to get out. Usually it cannot because the outside of the earth is too thick and strong.
But in some places the outside of the earth is thin and weak. Sometimes a crack appears. The hot melted rock, which we call "lava" (熔岩), pushes out through the crack and bursts through. Steam and gas shoot up into the air and the hot melted lava pours out. Big pieces of rock may be thrown high into the air.
After a while the volcano becomes quiet again. The melted lava becomes hard. Later the same thing happens again and again. Each time more hot lava pours out on top of the cold lava and then becomes hard. In this way a kind of mountain is built up, with a hole down the middle. Perhaps the volcano will then be quiet. Perhaps it will start again hundreds of years later.
Vesuvius is the name of a very famous volcano in Italy. It first came to life many, many years ago. It was quiet for hundreds of years. Then in the year 79 it suddenly burst. A great cloud of smoke shot up into the sky with great burning rocks. Hot lava poured down its sides. About 3,000 people were killed.
This has happened again many times since that year. Sometimes no damage was caused, or only little damage. But there was serious damage in the years 472, 1631, 1794, 1861, 1872 and 1906. You can see that a volcano can stay alive for many years. There was also serious damage in 1914 but there has not been any since that year.
When lava cools, it becomes ______.

A:liquid B:water C:smoke D:hard

微信扫码获取答案解析
下载APP查看答案解析

您可能感兴趣的题目