许多学生随着自学能力的增强 ,由阅读课本深入到研读课本 ,从而引发出思考 ,提出了一些有价值的问题。现举例如下 :例 1 .物质的毒性是物质的物理性质 ,还是化学性质 ?从生物学的角度分析 ,物质的毒性应属于物质的化学性质 ,并非物理性质。如重金属盐 (Ｃｕ2 + ,Ｐｂ2 + ,Ｈｇ2 With the enhancement of self-study ability, many students have gone through reading textbooks to study textbooks, which led to thinking and raised some valuable questions. Examples are as follows: Example 1. The toxicity of a substance is the physical or chemical nature of the substance. From a biological point of view, the toxicity of a substance should belong to the chemical nature of the substance, not the physical properties. Such as heavy metal salts (Cu2 +, Pb2 +, Hg2