对于化学中存在的问题，有的可以用“一定”来说明，有的则应该用“不一定”来说明。欧正确使用“一定”与“不一定”，需要对有关问题做全面、客观、准确地分析。以下列举部分初中化学中的“不一定”，供学习参考。1．原子核不一定都由质子和中子构成。2．分子的质量不一定比 For the problems in chemistry, some can be described as “certain” and others as “not necessarily”. The correct use of “certain” and “not necessarily” by EU requires a comprehensive, objective and accurate analysis of relevant issues. The following is a list of some of the junior high school chemistry “not necessarily” for reference. 1. The nucleus does not always consist of protons and neutrons. 2. The molecular quality is not necessarily higher than