Is Matter Around Us Pure?
Chapter 2 of the Class 9 NCERT Science textbook teaches learners to judge purity scientifically. Elements and compounds count as pure substances, while air, soil and food reveal themselves as mixtures. Solutions, suspensions and colloids are distinguished by particle size, stability and the Tyndall effect, and Tyndall scattering, filtration and centrifugation become diagnostic tools. Evaporation, distillation, sublimation and chromatography then show how mixtures can be separated, proving that purity is established by testable properties rather than appearance.
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