Is Matter Around Us Pure 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 9 Science Revision Notes
- Matter in Our Surroundings
- Atoms and Molecules
- Structure of the Atom
- The Fundamental Unit of Life
- Force and Laws of Motion
- Work and Energy
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