CBSE Class 9th (Notes)
Chapter 2: Is Matter Around Us Pure
1. Matter
Anything that has mass and occupies space.
2. Pure Substance
A substance that consists of only one type of particle and has a fixed composition.
3. Element
A pure substance made up of only one kind of atom, which cannot be broken down into simpler substances by chemical means.
Example: Oxygen (O), Gold (Au).
4. Compound
A pure substance formed by the chemical combination of two or more elements in a fixed ratio.
Example: Water (H₂O), Carbon dioxide (CO₂).
5. Mixture
A combination of two or more substances that are physically mixed but not chemically combined.
6. Homogeneous Mixture
A mixture in which the composition is uniform throughout.
Example: Saltwater, Air.
7. Heterogeneous Mixture
A mixture in which the composition is not uniform and different components can be seen.
Example: Sand and iron filings, Oil and water.
8. Solution
A homogeneous mixture of two or more substances where the solute dissolves completely in the solvent.
Example: Sugar in water.
9. Solvent
The substance in which the solute dissolves to form a solution.
Example: Water in saltwater.
10. Solute
The substance that dissolves in a solvent to form a solution.
Example: Salt in saltwater.
11. Suspension
A heterogeneous mixture in which solute particles do not dissolve but remain suspended in the medium.
Example: Mud in water.
12. Colloid
A mixture where small particles are evenly spread throughout another substance and do not settle down over time.
Example: Milk, Fog.
13. Tyndall Effect
The scattering of light by particles in a colloid or suspension, making the path of light visible.
Example: Light passing through fog.
14. Filtration
A method used to separate insoluble solids from liquids by using a filter.
Example: Separating sand from water.
15. Evaporation
A separation technique used to remove a liquid from a solution by heating, leaving the solute behind.
Example: Obtaining salt from seawater.
16. Distillation
A method used to separate liquids based on their boiling points.
Example: Separating alcohol from water.
17. Chromatography
A technique used to separate components of a mixture based on their different rates of movement in a medium.
Example: Separating colors in ink.
18. Sublimation
A process in which a solid changes directly into a gas without passing through the liquid state.
Example: Camphor, Iodine.
19. Physical Change
A change in which no new substance is formed and only the physical properties change.
Example: Melting of ice, Tearing of paper.
20. Chemical Change
A change in which a new substance with different properties is formed.
Example: Rusting of iron, Burning of wood.
AIM STUDY POINT
