SCIENCE - CLASS IX - IS MATTER AROUND US PURE
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- Pure Substance: Single type of particles with fixed composition. Examples: Elements (Gold, Oxygen) and Compounds (Water, Salt).
- Mixture: Two or more substances mixed physically. Variable composition. Types: Homogeneous and Heterogeneous.
- Homogeneous Mixture: Uniform composition throughout. Examples: Salt solution, Sugar solution, Air.
- Heterogeneous Mixture: Non-uniform composition. Examples: Mixture of salt and sand, Oil and water.
- Solution: Homogeneous mixture of solute and solvent. Particle size < 1nm.
- Suspension: Heterogeneous mixture where particles settle down. Particle size > 100nm.
- Colloid: Heterogeneous mixture with particle size 1-100nm. Shows Tyndall effect.
- Tyndall Effect: Scattering of light by colloidal particles making path visible.
- Concentration: Mass percentage = (Mass of solute/Mass of solution) × 100
- Saturated Solution: Contains maximum solute that can dissolve at given temperature.
- Unsaturated Solution: Can dissolve more solute at same temperature.
- Solubility: Maximum amount of solute that dissolves in 100g solvent at given temperature.
- Separation Techniques: Filtration, Centrifugation, Sublimation, Chromatography, Distillation, Fractional Distillation.
- Physical Change: No new substance formed. Reversible. Examples: Melting, Dissolving.
- Chemical Change: New substance formed. Irreversible. Examples: Burning, Rusting.
- Elements: 118 known elements (94 natural). Classified as Metals, Non-metals, Metalloids.
- Compounds: Formed by chemical combination in fixed proportion. Properties different from constituents.
Basic Level Questions
Chapter Summary
Chapter 2: Is Matter Around Us Pure explores the fundamental classification of matter into pure substances and mixtures. Pure substances include elements and compounds that have fixed composition and distinct properties, while mixtures are physical combinations of substances that can be separated using various techniques. The chapter systematically explains different types of mixtures - solutions, suspensions, and colloids - based on particle size and behavior.
We learn about essential separation methods like filtration, distillation, chromatography, and centrifugation, each suitable for specific types of mixtures based on differences in properties like solubility, boiling points, density, and magnetic behavior. The chapter also covers the distinction between physical and chemical changes, helping students understand when matter undergoes transformation without changing its chemical identity versus when new substances are formed.
This website provides extensive practice through carefully crafted multiple-choice questions that help students master the classification of matter, understand separation techniques, and distinguish between physical and chemical changes. The questions cover all key concepts from basic definitions to complex applications, enabling students to:
- Identify different types of mixtures and pure substances
- Understand appropriate separation methods for various mixtures
- Calculate concentrations and solubility
- Differentiate between physical and chemical changes
- Prepare effectively for board exams and competitive tests
With detailed explanations for each answer, students can clarify doubts, strengthen conceptual understanding, and develop problem-solving skills essential for academic success in science.