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质量守恒定律是化学的一个基本定律。同学们要在实际题目中能熟练运用此定律,必须对这一概念有透彻的理解。从宏观角度理解,化学反应前后,物质发生了改变(即有新物质生成),而组成物质的元素种类始终不变;从微观角度理解,化学反应前后,分子本身发生了改变,而分子的数目有的不变,有的改变,原子的种类和数目都不改变(显然,包括在原子中的原子核、质子、中子、电子在化学反应前后本身也不发生改变)。当对质量守恒定律的概念有了上述深刻理解之后,就可以将定律浓缩成下面的“四个守恒”: ①物质的质量总和守恒;
The law of conservation of mass is a basic law of chemistry. Students must be able to use this law skillfully in practical subjects and must have a thorough understanding of the concept. From the macroscopic point of view, before and after the chemical reaction, the substance has changed (that is, new substances have been generated), and the types of elements that make up the substance have remained unchanged; from the microscopic point of view, before and after the chemical reaction, the molecules themselves changed, and the number of molecules Some are unchanged, some are changed, and the type and number of atoms do not change (apparently, the nucleus, protons, neutrons, and electrons included in the atom do not change themselves before and after the chemical reaction). After having a profound understanding of the concept of the law of conservation of mass, the law can be condensed into the following “four conservations”: 1 The sum of mass of matter is conserved;