第一单元?Types of Materials材料的类型Materialsmay be grouped in severalways. Scientistsoften classifymaterialsby theirstate:solid, liquid,or gas. They also separate them into organic (once living)and inorganic(never living)materials.材料可以按多种方法分类。科学家常根据状态将材料分为：固体、液体或气体。 他们也把材料分为有机材料( 曾经有生命的 ) 和无机材料 ( 从未有生命的 ) 。For industrialpurposes, materialsare divided into engineeringmaterialsor nonengineeringmaterials.Engineering materials are those use
