“密度”是初中物理的一个重要而抽象的概念，是九年义务教育初中物理教学大纲要求掌握的七个重点知识之一．同学们必须很好领会，深刻理解．为了帮助同学们正确理解“密度”这一概念，现提出以下几个值得注意的问题．一、“密度”反映了物质的一种特性我们已经知道体积相同的 “Density” is an important and abstract concept of junior high school physics, and it is one of the seven key knowledge required for the ninth-year compulsory education physics syllabus. The students must understand it well and have a deep understanding. In order to help students understand the concept of “density” correctly, the following issues are worth noting. First, “density” reflects a characteristic of matter that we already know