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学生在解答题意比较复杂的化学计算题时,主要困难是无从下手和思路混乱。针对这个问题,笔者以1985年化学高考题第六题第2小题为例,浅析化学计算题教学中的几个关键问题。一、剖析题型结构,抓住关键突破化学计算是从量的方面来反映物质及其变化规律的,它包括化学知识和数学运算两种因素,化学知识是基础,计算是工具。所以化学计算的基本方法是灵活运用有关的化学知识,抓住物质在化学变化中的“量的关系”、进行列式计算。对于题意比较复杂的化学计算,学生就难以和有关的化学知识挂钩联系,也就找不到准确的“量的关系”。解决的方法是:第一步剖析题型和结构,做到五“清”:
The main difficulty for students in answering the more complicated questions of chemical calculation is that they can not get started and their ideas are confused. In response to this problem, the author of the 1985 Chemical College Entrance Examination Question 6 Question 2 as an example, the analysis of several questions in the teaching of chemical calculation. First, the analysis of the question-type structure, to seize the key breakthrough Chemical calculation is reflected from the amount of matter and its changes in the law, which includes chemical knowledge and mathematical operations of two factors, chemical knowledge is the foundation, the calculation is a tool. Therefore, the basic method of chemical calculation is to flexibly use the relevant chemical knowledge, seize the “quantitative relationship” of substances in chemical changes, and calculate in the formula. For more complicated questions about chemistry calculation, students are difficult to link with the related chemical knowledge, and can not find accurate “quantity relationship.” The solution is: the first step to analyze the question type and structure, to achieve five “clear”: