“纯净物是由一种物质组成的”、“混合物是由两种或多种物质组成的,这些物质相互间没有发生化学反应,混合物里各物质都保持原来的性质”.要全面理解这组概念,可从以下四个方面进行辨析.一、纯净物有固定组成,混合物没有固定组成组成纯净物的物质只能是一种物质,组成混合物的物 “Pure substance is composed of one kind of substance” and “The mixture is made up of two or more kinds of substances. These substances have no chemical reaction with each other, and each substance in the mixture maintains its original nature.” To fully understand this group The concept can be distinguished from the following four aspects. First, the pure material has a fixed composition, and the mixture does not have a fixed composition. The material that constitutes the pure material can only be one kind of material, and the composition of the mixture is