现行新版的初二物理(华东版)上,把铁、钢的密度定为7.9,这与旧教材上的7.8相差了0.1,是印刷错误还是新规定?哪个正确哪个错误?这使好多物理教师大感迷惑。为此,笔者请教了编写教材的几位老师,答复综述如下: 教材上的铁是指纯铁,即含碳量为0％,这样的铁有三种:一种是熔点低于911℃,结构呈体心立方点阵 The current new edition of the 2nd physics (East China Edition) has set the density of iron and steel to 7.9, which is a difference of 0.1 from the old teaching material of 7.8. Is it a printing error or a new rule? Which is correct or not? This makes a lot of physics teachers Feeling confused. To this end, the author consulted several teachers who wrote textbooks. The answer is summarized as follows: The iron in the textbook refers to pure iron, ie, the carbon content is 0%. There are three kinds of iron: one is the melting point lower than 911°C, and the structure is Body-centered cubic lattice