Is Matter Around Us Pure Class 9 Science — Revision Notes
Pure substances have fixed physical and chemical properties, while mixtures are combinations of two or more substances that retain individual properties. T
TL;DR: Pure substances have fixed physical and chemical properties, while mixtures are combinations of two or more substances that retain individual properti…
Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated
Pure substances have fixed physical and chemical properties, while mixtures are combinations of two or more substances that retain individual properties. T
Classification of Matter
- Pure substances: elements (atoms of one type) and compounds (chemically bonded atoms)
- Mixtures: homogeneous (uniform composition) and heterogeneous (visible different components)
Elements vs Compounds
- Elements: made of only one type of atom, cannot be decomposed by chemical methods
- Compounds: made of two or more elements in fixed ratio, have different properties from constituent elements
- Compounds can be decomposed into elements by chemical reactions
Solutions and Colloids
- Solutions: homogeneous mixtures with particles <1 nm, solute dissolved uniformly
- Colloids: heterogeneous mixtures with particles 1-1000 nm, show Tyndall effect
- Suspensions: heterogeneous mixtures with particles >1000 nm, particles visible and settle over time
Separation Techniques
- Filtration: separates insoluble particles from liquid
- Evaporation: obtains dissolved solid from solution
- Distillation: separates miscible liquids by boiling point difference
- Chromatography: separates components based on solubility and motion
- Magnetic separation: uses magnetic properties to separate components
Properties of Mixtures vs Pure Substances
- Pure substances: fixed melting and boiling points, uniform composition, definite properties
- Mixtures: no fixed melting/boiling points, variable composition, variable properties
Key Terms
- Pure Substance: Matter with definite composition and fixed physical/chemical properties
- Mixture: Combination of two or more substances that retain individual properties
- Homogeneous Mixture: Mixture with uniform composition throughout
- Heterogeneous Mixture: Mixture with visibly different components
- Tyndall Effect: Scattering of light by colloidal particles
- Solvent: Component present in larger amount in a solution
- Solute: Component dissolved in solvent in a solution
Frequently Asked Questions
Is air a mixture or a pure substance?
Air is a homogeneous mixture of nitrogen, oxygen, and other gases in variable composition.
Why does salt water boil at a higher temperature than pure water?
Salt dissolved in water is a mixture with no fixed boiling point; the added solute raises the boiling point above 100°C.
How does distillation separate two liquids?
Distillation heats the mixture to boil the liquid with lower boiling point first, condenses its vapor, and separates it from the remaining liquid.
More Class 9 Science Revision Notes
- Matter in Our Surroundings
- Is Matter Around Us Pure
- Atoms and Molecules
- Structure of the Atom
- The Fundamental Unit of Life
- Tissues
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