“质量守恒定律”这一节课，引导学生从量的方面去研究化学反应的客观规律，为化学方程式的教学作好理论准备，这是学好第四章《化学方程式》的基础。“质量守恒定律”涵义的理解和运用，既是本章的重点也是难点。教师在教学中要注意创设问题情境，通过准确的实验，启发诱... The “law of conservation of mass” lesson guides students to study the objective laws of chemical reactions from the aspect of quantity and to make theoretical preparations for the teaching of chemical equations. This is the basis for learning the fourth chapter “Chemical Equations”. The understanding and application of the meaning of “law of conservation of mass” are both the focus and the difficulty of this chapter. Teachers should pay attention to the creation of problem situations in teaching, and through accurate experiments, inspire...