A-level考试中，很多同学在科目的选择上，都偏向选择理科，尤其是化学科目，更是受到了大家的一致欢迎，不过很多同学在化学科目的备考上，还存在很多问题，毕竟A-level化学科目是一个相对而言比较重视理论与实践相结合的学科。今天，小编要为大家介绍的是A-level化学考试中的知识点：共价化合物。
Properties of Covalent Compounds
共价化合物的物理性质
melting points and boiling points
熔点和沸点
Most covalent compounds have relatively low melting points and boiling points.
大多数共价化合物具有相对低的熔点和沸点。
While the ions in an ionic compound are strongly attracted to each other, covalent bonds create molecules that can separate from each other when a lower amount of energy is added to them.
离子化合物中的离子彼此强烈吸引，而共价键产生的作用力并没有这么强，所以他们彼此之间很容易分离 。
Therefore, molecular compounds usually have low melting and boiling points.
因此，共价化合物通常具有低熔点和低沸点。
Covalent compounds usually have lower enthalpies of fusion and vaporization than ionic compounds.
共价化合物通常比离子化合物具有更低的熔化和蒸发焓。
flexible
韧性
Covalent compounds tend to be soft and relatively flexible.
共价化合物一般比较柔软且相对柔韧。
This is largely because covalent bonds are relatively flexible and easy to break.
这主要是因为共价键相对灵活且易被破坏。
The covalent bonds in molecular compounds cause these compounds to take form as gasses, liquids, and soft solids.
分子化合物中的共价键使这些化合物形成气体，液体和软固体。
conduct electricity
导电性
When dissolved in water, covalent compounds don't conduct electricity.
当共价化合物溶解在水中时，不导电。
Ions are needed to conduct electricity in an aqueous solution.
水溶液导电需要电子。
Molecular compounds dissolve into molecules rather than dissociate into ions, so they typically do not conduct electricity very well when dissolved in water.
分子化合物溶解成分子而不是离解成离子，所以当它们溶解在水中时通常不能很好地导电。
dissolvability
溶解性
Many covalent compounds don't dissolve well in water.
许多共价化合物在水中不能很好地溶解。
There are many exceptions to this rule, just as there are many salts (ionic compounds) that don't dissolve well in water.
当然也存在例外，就像许多盐（离子化合物）在水中不能很好地溶解一样。
However, many covalent compounds are polar molecules that do dissolve well in a polar solvent, such as water.
许多共价化合物是极性分子，其在极性溶剂（例如水）中可以很好地溶解。
Examples of molecular compounds that dissolve well in water are sugar and ethanol.
在水中可以溶解的共价化合物的例子有糖和乙醇。
Examples of molecular compounds that don't dissolve well in water are oil and polymerized plastic.
在水中不能很好溶解的共价化合物的例子有石油和聚合塑料。
以上就是本文有关A-Level化学考试共价化合物的相关介绍了，希望能够对大家有所帮助。了解更多有关alevel化学词汇、alevel考试报名网站等相关内容，可咨询在线客服。
