Class IX Science
Notes for Is matter Around Us Pure
Facts that Matter
•Compounds
Compound is a pure substance made up of two or more elements combined chemically in a definite ratio.
Characteristics:
1.The properties of compound differ from those of its constituents.
2.Compound has fixed melting point and boiling point.
3.Compound is a hom*ogeneous substance.
4.Constituent elements can be separated by chemical process.
•Mixtures
It is made up of two or more elements or compounds mixed in any ratio/proportion.
Properties:
•It may be hom*ogeneous of heterogeneous.
•The properties of constituent substances are retained.
•No new compound is formed.
•Elements can be separated by simple physical processes.
•It does not have fixed melting and boiling point.
Separation of Mixtures:
| Type of Mixture | Separation method |
| 1. Two immiscible liquids. Example, oil + water | By using separating funnel |
| 2. Ammonium chloride + sand | Sublimation |
| 3. Dyes in black ink. (One solvent different constituents) | Chromatography |
| 4. Two miscible liquids. (Acetone + water) | Distillation |
| 5. Solid particles insoluble from (solvent) liquid. (Milk + Cream) | Centrifugation |
Physical and Chemical Change
| Physical Change | Chemical Change |
| (i) No new substance is formed. | A new substance is formed. |
| (ii) Properties of constituent elements/substance is retained. | Properties of constituent elements/substance changes. |
| (iii) Change does not involve loss or gain of heat. | Loss or gain of heat may be involved in this reaction. |
| (iv) This change is generally reversible. | This change is generally irreversible. |
•Solution
It is a hom*ogeneous mixture of two or more substances.
| Solute | Solvent |
| A substance which is dissolved in a solvent. E.g., salt, sugar. | Liquid part of solution in which is dissolved. E.g., water. |
| Solute can be solid, liquid or gas. | Solvent can be liquid, solid or gas. |
| Suspension | Solvent |
| (i) Size of soluteparticles are visible with naked eyes | Size of solute particles are not visible with naked eyes. |
| (ii) Shows tyndall effect | Shows tyndall effect |
| (iii) Translucent | Translucent |
| (iv) Solute particles settle Down | Colloidal particles do not settle down |
•Different Types of Colloids
| Dispersed Phase | Dispersing Medium | Type | Example |
| Liquid | Gas | Aerosol | Fog, clouds, mist |
| Solid | Gas | Aerosol | Smoke, automobile exhaust |
| Gas | Liquid | Foam | Shaving cream |
| Liquid | Liquid | Emulsion | Milk, face cream |
| Solid | Liquid | Solution | Milk of magnesia, mud |
| Gas | Solid | Goam | Sponge, pumice |
| Liquid | Solid | Gel | Jelly, cheese, butter |
| Solid | Solid | Solid sol | Coloured gemstone, milky glass |
