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大家知道,一般物质的沸点都比其熔点高,但高中化学课本中给出的“几种炔烃的物理性质”表中,乙炔的沸点(-84.0℃)却比其熔点(-80.8℃)低。这是什么原因呢? 原来,乙炔的沸点和熔点在物理意义上与一般物质不同。高中化学课本中给出的乙炔的沸点(-84.0℃),实际上并不是常压下乙炔由液态转变成气态时的温度,而是乙炔在760 mmHg压力下由固态直接转变成气态时的温度。因此,确切地讲,-84.0℃应是乙炔的升华点。至于乙炔的熔点(-80.8℃),也并非是指
As we all know, the boiling point of the general substance is higher than its melting point, but the boiling point (-84.0°C) of acetylene is higher than its melting point (-80.8°C) in the “physical properties of several alkynes” given in the high school chemistry textbook. low. What is the reason for this? Originally, the boiling point and melting point of acetylene were different from the general substance in the physical sense. The boiling point (-84.0°C) of acetylene given in high school chemistry textbooks is not actually the temperature at which acetylene is converted from liquid to gaseous at atmospheric pressure, but is the temperature at which acetylene is directly converted from a solid state to a gaseous state at a pressure of 760 mmHg. . Therefore, exactly -84.0 °C should be the sublimation point of acetylene. As for the melting point of acetylene (-80.8°C), it does not mean