[教材和学情分析]教材通过小明与小华的对话,将学生所熟悉的物体即铁钉和大头针进行比较,从而使学生认识到不同物体所含物质的多少不一定相同,进而引出质量的概念。接着介绍了质量的单位及换算。质量是物理学中的重要概念,它是物体惯性大小的量度,而且通过爱因斯坦质能方程可以知道,质量又与能量相联系,这些知识将在高中物理中学习。初中阶 [Textbook and academic analysis] textbooks through the dialogue between Xiao Ming and Xiaohua, students will be familiar with the object that is nails and pins to compare, so that students recognize that different objects contained in the number of not necessarily the same, and then lead to quality concept. Then introduced the quality of the unit and conversion. Quality is an important concept in physics. It is a measure of the inertia of an object. It is also known from Einstein’s equation of mass, which is related to energy, and this knowledge is to be learned in high school physics. Junior high school