Is Matter Around Us Pure?

It's the lesson two of class 9th (Science) NCERT. The topics included are- Pure, Substance, Mixture, Homogeneous and Heterogeneous Mixtures, Solution, Colloid, Suspension, Comparative study, Evaporation, Centrifugation, Separating Funnel, Sublimation, Chromatography, Distillation, Fractional Distillation, Separating Gases, Crystallization, Physical and Chemical Changes, Elements, Compounds, Mixture v/s Compound