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一、以问题教学带动学生进行研究性学习的案例1.发现问题,展开讨论高二化学有关铁及其化合物的教学中,总会碰到Fe~(2+)和 Fe~(3+)的鉴别问题,高中教学中对于 Fe~(2+)只能采用加入 NaOH 溶液,通过生成的沉淀颜色变化来加以鉴别。演示实验:在一试管中加入 FeSO_4溶液,然后将一个盛有 NaOH 溶液的长胶头滴管插入 FeSO_4溶液液面下(违反常规操作),挤压胶头滴管,使 NaOH 溶液和 FeSO_4溶液反应生成白色 Fe(OH)_2沉淀。观察沉淀由白色变成灰绿色再变成红褐色,以此来判断Fe~(2+)的存在。
First, the problem-based teaching to drive students to study case study 1 found the problem, to discuss the chemical chemistry of iron and its compounds in teaching, always encounter Fe ~ (2+) and Fe ~ (3 +) identification Problem, high school teaching for Fe ~ (2+) can only be added by NaOH solution, by the formation of precipitation color change to be identified. Demonstration experiment: FeSO_4 solution was added to a test tube, then a long rubber dropper filled with NaOH solution was inserted into the FeSO_4 solution (in violation of normal operation), and the rubber dropper was squeezed to make NaOH solution and FeSO_4 solution react A white Fe (OH) 2 precipitate was formed. Observed precipitation from white to gray-green and then into a red-brown, in order to determine the presence of Fe ~ (2+).