“变式训练”是指在不改变关键内容的前提下 ,变换关键内容的呈现方式所进行的训练。坚持“变式训练” ,对学生系统地、牢固地掌握所学知识 ,提高思维的灵活性 ,培养解题能力 ,都是很有意义的。例如 :铁与浓、稀硝酸的反应 ,是高中化学中的一个重点 ,也是一个难点。其实质是铁 “Variable training” refers to the training of changing the presentation of key content without changing the key content. Adhering to “transformation training” is of great significance for students in systematically and firmly grasping what they have learned, improving their flexibility of thinking, and developing problem-solving abilities. For example: The reaction of iron with concentrated, dilute nitric acid is a key point in high school chemistry, and it is also a difficult point. The essence is iron