2019年12月英语六级阅读模拟训练 The difference between a liquid and a gas is obvious under the conditions
of temperature and pressure commonly found at the surface of the Earth. A liquid
can be kept in an open container and fill it to the level of a free surface. A
gas forms no free surface but tends to diffuse throughout the__1__available; it
must therefore be kept in a closed container or held by a gravitational field,
as in the__2__of a planet's atmosphere. The distinction was a __3__feature of
early theories describing the phases of matter. In the nineteenth century, for
example, one theory maintained that a liquid could be "dissolved" in a vapor
without losing its identity, and another theory__4 __that the two phases are
made up of different kinds of molecules. The theories now prevailing take a
quite different approach by emphasizing what liquids and gases have in __5
__They are both forms of matter that have no __6 __structure, and they both flow
readily.
The fundamental similarity of liquids and gases becomes clearly apparent
when the temperature and pressure are __7__somewhat. Suppose a closed container
__8__filled with a liquid is heated. The liquid expands, or in other words
becomes less dense; some of it evaporates. In contrast, the vapor above the
liquid surface becomes denser as the evaporated molecules are __9__to it. The
combination of temperature and pressure at which the densities become __10__is
called the critical point.
A. added B. case C. prominent D. held
E. equal F. partially G. example H. previous
I. space J, lifted K. permanent L. particularly
M. extended N. raised O. common
答案：
I. I 2. B 3. C 4. D 5. O 6. K 7. N 8. F 9. A 10. E
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