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“质量守恒定律”作为初中化学课程重点内容之一,它在历年的中考试题中重现率较高,是中考的热点。面对不断推陈出新的中考题型,特别是一些需要使用质量守恒定律的计算型中考题,许多同学会有困惑,有时还会出现无从下手的情形。事实上,从解题应用角度来看,质量守恒定律可理解归纳为“三个守恒”。一是反应前后物质的总质量守恒,二是反应前后元素的种类和质量不变,三是反应前后原子的种类、数目、质量都不变。巧妙运用这三个守恒的思想,就可以使我们的解题变得快捷,产生事半功倍的效果。
“Law of conservation of mass ” As one of the key contents of the junior high school chemistry course, it has a high recurrence rate in the middle school exams over the years and is a hot spot in the senior high school entrance examination. In the face of continuous improvement of the QSPEQ questions, especially some need to use the law of conservation of mass in the calculation of the exam, many students will be confused, and sometimes there is no way to start. In fact, from the perspective of problem solving, the law of conservation of mass can be summed up as “three conservation ”. First, before and after the reaction of the total mass of the material conservation, the second is the type and quality of the element before and after the reaction unchanged, the third is the type of atom before and after the reaction, the number of the same quality. Clever use of these three conservation ideas can make our problems faster and produce more with less.