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 11 available; it must therefore be kept in a closed container or held by a gravitational field, as in the 12 of a planet s atmosphere. The distinction was a 13 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 14 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 15 They are both forms of matter that have no 16 structure, and they both flow readily.
The fundamental similarity of liquids and gases becomes clearly apparent when the temperature and pressure are 17 somewhat. Suppose a closed container 18 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 19 to it. The combination of temperature and pressure at which the densities become 20 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
0.common
GRE词汇:考试词汇出现频率统计表29
GRE词汇:考试词汇出现频率统计表25
GRE词汇:考试词汇出现频率统计表33
新gre考试机考填空词汇16
新gre考试:新增词汇6
新gre考试新增词汇4
GRE词汇:考试词汇出现频率统计表10
gre词汇备考:常见词根词缀整理12
GRE词汇:考试词汇出现频率统计表16
新gre考试机考填空词汇7
新gre考试:新增词汇1
GRE词汇:考试词汇出现频率统计表26
新gre考试机考填空词汇17
GRE词汇:考试词汇出现频率统计表15
GRE词汇:考试词汇出现频率统计表35
GRE词汇:考试词汇出现频率统计表30
GRE词汇:考试词汇出现频率统计表9
新gre考试机考填空词汇6
新增gre考试词汇1
新gre考试机考填空词汇10
新gre考试机考填空词汇12
GRE词汇:考试词汇出现频率统计表37
GRE词汇:考试词汇出现频率统计表40
新gre考试:新增词汇3
新g词汇:implement考法及近、反义词解析
新增gre考试词汇3
新增gre考试词汇2
gre词汇备考:常见词根词缀整理3
GRE词汇:考试词汇出现频率统计表27
新gre考试机考填空词汇3
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