Mass is measured by the amount of force required to change an object's direction or speed. Chemists classify matter in order to better understand and describe it. It takes the shape and volume of the container. It is an easily compressed fluid. A pure substance is a homogeneous form of matter which has a definite or constant composition and distinct properties.
Every bit appears the same.
Today we can detect one in a trillion parts of impurity of some substances. A pure substance can be identified by appearance, smell, and other properties. All specimens of the same pure substance have identical composition, color, chemical and physical properties including a constant melting point and a constant boiling point. Mixtures vary in composition. This is accomplished by techniques such as filtration, sublimation, distillation, fractional crystallization, and all kinds of chromatography.