笔者有幸分别听到不同学校的两位教师教初二物理“密度”一节课.一位教师未做课本里给出的两个实验和其替代实验,只是简略叙述书本上一段文字后,就从抽象数学出发,指出:同一种物质的物体质量与体积之比为一定值; The author had the privilege to hear two teachers of different schools teach the first day of physical “density” lesson. A teacher did not do two experiments given in the textbook and its alternative experiment, but after briefly narrating a paragraph of text in the book, Starting from the abstract mathematics, it is pointed out that the ratio of the mass and volume of the same substance is a certain value;