请在这里输入关键词：
科目：高中英语
阅读下列短文, 从所给的四个选项中, 选出最佳答案。　　
　　&&& Milan, the second largest city of Italy, has won an undesirable　　
(不受欢迎的) world record. Of the 54 big cities studied by the World　　
Health Organization and the United Nations, Milan was considered to　　
have the worst air pollution.　　 　　
　　&&& According to these two 10-year studies, the level of air pollution　　
in Milan is twice as high as the levels in Paris and Beijing and three　　
times those in Tokyo and London, and four times that in New York.　　
　　 &&& The reason for Milan's bad pollution, according to the scientists,　　
is that the city is situated in a valley that holds back the poisonous　　
　　 &&& Though Milan has taken some measures to lower the level of　　
pollution, the situation is still worrying. People joke about each　　
other, &If you're travelling to Milan, be sure to bring your gas mask.&　　
(1) &Which&is&not&mentioned&in&the&passage?&&
A.&The&reason&for&the&air&pollution&in&Milan.　　
B.&The&measures&taken&by&Milan&to&solve&the&problem.&&&
C.&The&city's&air&regarded&to&be&worst&polluted.&&
D.&The&conclusion&that&the&air&in&Milan&was&badly&polluted.　　
(2) &Which&of&the&following&correctly&shows&the&level&of&air&pollution&
in&Milan?&
　　&&A.& 　　
　　B.& 　　&
&&& C.& 　　 & &&D.& &&&
(3) &Why&is&the&air&pollution&in&Milan&so&serious?
A.&Because&the&city&lies&in&a&place&where&it&is&difficult&for&&&polluted&air&to&move&away.
B.&Because&too&many&cars&are&being&driven&in&the&city.
C.&Because&the&city&has&some&mountains.&
D.&Because&Milan&has&taken&some&worrying&measures.&&
(4) This&passage&tells&us&__________.&
A.&it&is&quite&easy&to&breathe&the&air&in&Milan
B.&it&is&dangerous&to&breathe&the&air&in&Milan
C.&it&is&impossible&to&travel&in&Milan&without&a&gas&mask
D.&it&is&funny&to&travel&in&Milan&with&a&gas&mask
科目：高中英语
______ with a gas lighter than air, a balloon can float in the air．
A．When filled 　　　B．Filling
C．Having filled 　　D．When filling
科目：高中英语
来源：浙江省金华一中学年高二上学期期中考试英语试题（中加班）（人教版）
Reading Comprehension
　　Men always wanted to fly．For hundreds of years they watched birds flying and wished that they could fly too．Birds fly very easily．They beat the air with their wings and climb up through the air．The air keeps them up．
　　Men knew how to make kites hundreds of years ago．Kites could stay in the air for many hours．“If birds and kites stay up in the air, perhaps we can,” they thought．
　　At first they made wings like birds．Then they jumped off high buildings and tried to fly．Many men did this but they failed to fly．They crashed to the ground．Some were killed and some were badly hurt．After many times they stopped trying to fly with wings．Then two brothers tried another way．They tried balloons．“Hot air is lighter than cold air,” they said．“That is why hot air goes upwards．If we fill a balloon with hot air it will go upwards．”
　　They built a balloon．It was made of thin cloth and paper．They lit a fire beneath it．Up into the air it went! It reached a height of 1, 800 meters．Then the air inside the balloon became cool and it slowly downed and gently rested on the ground．
　　A few months later the brother sent up another balloon．This time there was a basket hanging underneath it．In the basket there were three animals： a sheep, a duck and a hen．The balloon traveled through the air to a place two and half kilometers away．Then it came down safely to earth．Now it was time for men to fly! In October 1783 another of the brothers’ balloons went up．This time a man went with it．The balloon did not rise very far．It went, only to twenty－five meter．It was tied to the ground by a rope．A month later two men went up in a balloon full of hot air．This time there was no rope! A great crowd of people watched．The balloon rose to a height of 900 meters．The wind blew it along for nine kilometers．Then it came gently back to earth．Men had traveled through the air for the first time．
　　Other men filled the balloon with a gas called hydrogen．Hydrogen is much lighter than air．Balloon filled with it were able to travel long distances．But the men in the basket underneath could not steer them．They went where the wind took them．
　　Later balloons were made in the shape of a cigar．These were called airships．They had engines to drive them alone, and they could be steered a little．But they were still blown about by the wind．The hydrogen gas was dangerous, too．It caught fire very easily．There were many accidents and many people died．At last they stopped making airships．
When some men tried to fly with wings, ________．
a few of them succeeded
none of them succeeded
many of them succeeded
all of them succeeded
The first balloon were filled with ________．
Balloons were not a good way to travel because they ________．
went too high
went too low
had to be tied to the ground by a rope
could not be steered
Hydrogen was not a good gas for airships because it ________．
was the wrong shape
was too heavy
was too light
caught fire easily
科目：高中英语
1.&&&&& When filled with a gas lighter than air,a balloon can_____in the air.
A.fly　 B.float　
C.wander　
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ttuiwol361
ut the jailer closed the doorit could not be worse than it is now
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出门在外也不愁Universal Industrial Gases, Inc...Nitrogen N2 Properties, Uses, Applications -
Gas and Liquid
(N2) Properties, Uses and Applications
Nitrogen Gas and Liquid Nitrogen
Interesting
and Information about Nitrogen (N2):
Nitrogen (N2) is a colorless, odorless and tasteless gas that makes
up 78.09% (by volume) of the air we breathe.& It is nonflammable and
it will not support combustion.&&
Nitrogen gas is slightly lighter than air and slightly soluble in water.&
It is commonly thought of and
but it is not truly
inert.& It forms nitric oxide and nitrogen dioxide with oxygen,
ammonia with hydrogen, and nitrogen sulfide with sulfur.& Nitrogen compounds
are formed naturally through biological activity.& Compounds are also
formed at high temperature or at moderate temperature with the aid of catalysts. At high temperatures,
nitrogen will combine with active
metals, such as lithium, magnesium and titanium to form nitrides.&
is necessary for various biological processes, and is used as a
fertilizer, usually in the form of ammonia or
ammonia-based compounds.& Compounds formed with halogens and certain organic
compounds can be explosive.&
Nitrogen condenses at its boiling point, -195.8o C (-320.4o F), to a colorless liquid that is lighter than water.&
More nitrogen is used by customers than any other industrial gas.&
It is used in a broad range of industries, including chemicals,
pharmaceuticals, petroleum processing, glass and ceramic manufacture,
steelmaking and other metals refining and fabrication processes, pulp and
paper manufacture, and healthcare.& Aside from N2,
nitrogen may be referred to as GAN or GN in its gaseous form, and LIN or
LN in its liquid form.
Nitrogen is produced in large volumes in both gas and liquid
smaller volumes may be
produced as a gas by
.& Cryogenic processes
can produce very pure nitrogen.& Adsorption and diffusion processes are
typically used to
make lower purity product in relatively small amounts.& This is attractive
to users when purity
is not critical and alternatives (purchase of bulk liquid nitrogen, cylinders
of high pressure nitrogen, or local cryogenic production) are more
expensive or impractical.&
Gaseous nitrogen is valued for .&
It is used to shield potentially reactive materials from contact with
Liquid nitrogen is valued for .& When liquid nitrogen is vaporized and
warmed to ambient temperature, it
absorbs a large quantity& of heat.& The combination of inertness and its
intensely cold initial state makes liquid nitrogen an ideal coolant for
certain applications such as food freezing.& Liquid nitrogen is also used
to cool materials which are heat sensitive or normally soft to allow
machining or fracturing.& Examples are used tires, plastics,
certain metals and even pharmaceuticals.
English Units&
Normal Boiling Point
Gas Phase Properties
@ 32°F & @1 atm
Liquid Phase Properties
@ B P& @ 1 atm
Triple Point
Critical Point
Heat of Vaporization
Specific Gravity
Specific Heat (Cp)
Specific Gravity
Specific Heat (Cp)
BTU/lb °F
&Metric Units&&
Boiling Point
@ 101.325 kPa
Gas Phase Properties
@ 0° C & @ 101.325 kPa
Liquid Phase Properties
@ B.P., & @ 101.325 kPa
Triple Point
Critical Point
Heat of Vaporization
Specific Gravity
Specific Heat (Cp)
Specific Gravity
Specific Heat (Cp)
kJ/kg ° C
kJ/kg ° C
Nitrogen (N2)
Multi-Industry Uses for Nitrogen:
The inert properties of nitrogen make it a good
blanketing gas in many applications. Nitrogen
blanketing is used to protect flammable or explosive solids
and liquids from contact with air. Certain chemicals, surfaces of
solids, and stored food products have properties that must be protected from
degradation by the effects of atmospheric oxygen and moisture.& Protection
is achieved by keeping these items in (under) a nitrogen atmosphere. &Inerting& or
&padding& are other terms used to describe displacement of air and
nitrogen blanketing.
&Sparging&
with nitrogen is the bubbling of nitrogen gas through a liquid to remove
unwanted volatile components, including volatile organic compounds (VOC)
which may be necessary to meet pollution reduction regulations.
Certain substances are difficult to pulverize
or shred because they are tough or the materials will be degraded by the
heat generated by mechanical processes such as grinding.&
Liquid nitrogen can be used to freeze soft or tough substances prior to
their entering a size reduction process.& Cold vaporized nitrogen can
be used to keep materials cool (and in an inert atmosphere) during grinding.&
Cryogenic grinding is used in
diverse applications, including production of finely
ground pharmaceuticals, p and for shredding tires in
recycling plants.&
Manufacturing Uses for Nitrogen:
Nitrogen is used to treat the melt in the manufacture of steel and other metals and as a shield gas in the heat treatment of iron, steel and other metals.& It is also used as a process gas, together with other gases for reduction of carbonization and nitriding.
&“Flash” or “fins” on cast metal
can be removed by cooling with liquid nitrogen, making them brittle, allowing
then to be broken off by mechanical action.&
Manufacturing and Construction Uses:
Shrink fitting is an interesting alternative to traditional expansion fitting.& Instead of heating the outer metal part, the inner part is cooled by liquid nitrogen so that the metal shrinks and can be inserted.& When the metal returns to its normal temperature, it expands to its original size, giving a very tight fit.
Liquid nitrogen is used to cool concrete, which leads to better cured
properties.
construction operations must be done in soft, water-soaked ground such as tunnel construction underneath waterways, the ground can be frozen effectively with liquid nitrogen.&Pipes are driven into the ground, liquid nitrogen is pumped through the pipes under the earth’s surface. When the nitrogen exits into the soil, it vaporizes, removing heat from the soil and freezing it.
Chemicals, Pharmaceuticals and Petroleum Uses:
Refineries, petrochemical plants and marine tankers use nitrogen to purge equipment, tanks and pipelines of dangerous vapors and gases (for example, after
completing a pipeline transfer operation or ending a production run)
and to maintain an inert and&protective atmosphere in tanks storing flammable liquids.
Cold nitrogen gas is used to cool reactors filled with catalyst during maintenance work.&The cooling time can be reduced substantially.
reactors (and the materials inside) to low temperature allows better control of side-reactions in complex reactions
in the pharmaceutical industry. Liquid nitrogen is often used to provide
the necessary refrigeration as it can produce rapid temperature reduction
and easily maintain the required cold reaction temperatures.& Reactor cooling and
temperature control systems usually employ a
circulating low-temperature heat transfer fluid to transfer refrigeration
produced by vaporizing liquid nitrogen to the
shell of the
reactor vessel.& The liquid nitrogen is vaporized in specially-designed
heat exchangers that transfer refrigeration to the circulating heat
transfer fluid.
Liquid nitrogen is used during well completion to &frac&
natural gas bearing rock formations, in particular, tight gas formations,
including shale gas and natural gas from coal (coal bed methane)
where water based methods should be avoided.
Nitrogen is also used to maintain pressure in oil and natural gas
producing formations.& Unlike carbon dioxide, which is also used for
pressurization, nitrogen has little
affinity for liquid hydrocarbons, thus it builds up in and remains
in the gas cap.
Nitrogen is used an inert gas to push liquids though lines, to clear lines
and to propel &pigs& through pipelines to sweep out one material before
using the line to transport another material.
Rubber and
Plastics Industry Uses:
Materials become hard and brittle when cooled by to very low temperatures.& This property permits the removal of “flash” or “fins” on cast
plastics and rubber.& The castings are cooled by liquid nitrogen and the flash broken off by mechanical action.&
and Beverages:
The intense cold
liquid nitrogen allows very rapid freezing of food items, resulting in minimal
cell damage from ice crystals and improved appearance, taste and texture.
Well-designed cryogenic tunnel and spiral freezers efficiently capture
refrigeration from liquid vaporization and from the cold nitrogen gas as it flows
through the freezer.
When substances such as vegetable oil and wines are stored, the inert properties of nitrogen can be used to
protect against loss of quality by oxidation by expelling any air entrained in the liquid (“sparging”)
and protecting liquids in storage tanks by filling the vapor space (“blanketing”).&&
Nitrogen (and nitrogen
mixed with CO2 and oxygen) is used in transport trucks and in Modified Atmosphere Packaging (MAP) to
extend the shelf life of packaged foods by preventing oxidation, mold, insect
infestation and moisture migration.
Care Uses:
Nitrogen is
used as a shield gas in the packing of some medicines to prevent
degradation by oxidation or moisture adsorption.
Nitrogen is used to
freeze blood, as well as viruses for vaccination.&It is also used to freeze livestock semen, which can then be stored for years.
The quick freezing resulting from the intense cold minimizes cell wall damage.
Liquid nitrogen is also used in some MRI (Magnetic
Resonance Imaging) devices to pre-cool the low temperature magnets prior
to using much more expensive liquid helium for final cooling.
Liquid nitrogen is used in cryo-surgery to destroy diseased tissue.&
Miscellaneous Uses for Nitrogen:
Nitrogen is
used directly as a coolant for severe environmental testing of many items,
or as a refrigeration source for chilling circulating dry air.
Nitrogen Safety: Material
Safety Data Sheets and related Information:
Properties, Applications and Uses
of Other Industrial Gases:
Information on Technology,
Product Supply Optimization, UIG Plants & Services:
Universal Industrial Gases, Inc.
2200 Northwood Ave.
Suite 3Easton, Pennsylvania
Phone (610) 559-7967 Fax (610) 515-0945
All material contained herein Copyright 2003
/ 2009 UIG.&
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