CBSE Class 9 Chemistry, Is Matter Around Us Pure

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 homogeneous 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 homogeneous 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 homogeneous 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