Phases of a Pure Substance Phase refers to a quantity of matter that is homogeneous throughout in both chemical composition and physical structure (a) (b) (c) (a)Solid:molecules oscillate about "fixed"positions (b)Liquid:groups of molecules float about each other (c)Gas:gas molecules move randomly 上游究通大学 March 12,2019 5 SHANGHAI JLAO TONG UNIVERSITYMarch 12, 2019 5 Phases of a Pure Substance (a) Solid: molecules oscillate about “fixed” positions (b)Liquid: groups of molecules float about each other (c)Gas: gas molecules move randomly Phase refers to a quantity of matter that is homogeneous throughout in both chemical composition and physical structure