Chapter 2

Facts that matter

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Matter: two types of matter

1- pure substance

2- impure substance( Mixtures)

1) Pure substance - pure substance are again of two types

(A) - elements. (B) - compounds

(A) Elements : it is a pure substance which can not be spilit into two or more simpler substances.

Elements are further grouped into the following three categories.

(a) Metals - malleable, ductile, good conductors of heat.

Ex. - copper, gold,iron

(b) Metalloids - shows some properties of metals and some of non-metals.

Ex.- silicon,boron, arsenic,

(c) Non metals - non malleable, non ductile bad conductors of heat.

Ex.- sulphur, oxygen.

(B) Compounds - the compound is a pure substance made up of two or more elements combined chemically in a definite ratio.

Ex.- water,sugar,salt, etc.

Characteristics :

  • The properties of compound differ from those of its constituents.

  • Compound has fixed melting point and boiling point.

  • Compound is a homogeneous substance.

  • Constituent elements can be separated by chemical process.

2) Impure substances (mixtures)- It is made up of two or more elements or compounds mixed in any two ratio / proportion.

It is of two types :

(A)Homogeneous- uniform composition

Ex.- sugar+H2O,water+alcohol

(B)Heterogeneous - non uniform composition

Ex.- sand+ sugar, water+ oil.

Properties -

  • It may be homogeneous or heterogeneous.

  • The properties of constituent substances are retained.

  • No new compound is formed.

  • Elements can be separated by simple physical process.

  • It does not have a fixed melting and boiling point.

Separation of mixtures-

Physical and Chemical Changes

Solutions- It is homogeneous mixture of two or more substances.

1) Solute - A substance which is dissolved in a Solvent. E.g. salt Sugar. Solute can be solid Liquid,or gas.

2) Solvent - liquid part of Solution in Which a Substance is dissolved. E.g. - Water ,Solvent can be liquid,solid,gas.

Types of solution----

1) Aqueous solution- A solution in which water is a solvent.

Ex.- salt+ water

2) Non-aqueous solution- A solution in which water is not a solvent.

Ex.- salphar+ Carbon diosulphide

3) True Solution - solute particles completely dissolve in solvent and are not visible.

Ex.- sugar+ water

4) Saturated Solution- A Solution in which no more solute can dissolve

at given temperature.

5) Unsaturated Solution- A Solution in which more solute can dissolve at a given temperature.

6) Solution can be dilute or concentrated - Depending upon the amount of solute dissolving in solvent.

Suspensions :

  • Size of solute particles are visible with naked eyes.

  • Shows Tyndall effect

  • Translucent

  • Solute particles settle down

Colloidal Solution:

  • Size of solute particles are not visible with naked eyes

  • Shows Tyndall effect

  • Translucent

  • Colloidal particles do not settle down

Different types of colloids

We hope CBSE/MP Board Class 9th Science Chapter 2 "Is Matter Around us" will help you.

Written By - Divya Bhadouriya & Himanshu Sharma