一、知识比较二、韵语巧记物变化变都在变，有无新质来分辨；物变形变状态变，化变质变分子变；化变同时伴物变，物变不必有化变。三、疑难问答回．有发光、放热、变色或者产生气体的变化一定是化学变化吗？答：不一定。在化学变化过程中，常常伴随发生一些现象，如放热、发光? First, knowledge comparison Second, rhyme clever notes changes are changing, there is no new quality to distinguish; object deformation change state, change metamorphosis of molecular change; metamorphosis at the same time with concomitant changes, material changes do not have to change. Third, difficult questions and answers. Is there a change in light emission, exotherm, discoloration, or gas evolution? Answer: Not necessarily. In the process of chemical change, there are often some phenomena, such as heat release and light emission.