''AKC SCIENCE CLASSES"
CLASS 09 TH (CBSE AND MP BOARD)
"CHAPTER 02"
"IS MATTERS AROUND US PURE"
"BASIC CONCEPTS"
1) Pure Substance & Mixture.
| SL.No. | Pure Substance | Mixed Substance | |
|---|---|---|---|
| 1 | Pure substance consists of a single type of substance. | Mixture consists of two or more pure substances. | |
| 2 | Pure substance cannot be separated into other substances by physical methods. | Mixture can be separated into its components by physical methods. | |
| 3 | Pure substance has its own definite properties | Mixture shows the properties of its components. |
Elements are made up of one kind of atoms only. Compounds are made up of one kind of molecules.
(2). Types of Mixtures :-
(a). Mixture can also be grouped on the basis of their physical states :-
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(b). On the basis of miscibility :-
| SL No. | HOMOGENEOUS MIXTURE | HETEROGENEOUS MIXTURE | |
|---|---|---|---|
| 1. | It consists of single phase. | It consists of two or more phases. | |
| 2. | Uniform composition. | Does not have uniform composition. | |
| 3. | Example:- Sugar dissolved in water. | Example:- Air, sand and common salt. |
(3). Separating the components of a mixture :-
The components of a heterogeneous mixture can be separated by
- Simple methods like :- hand picking, sieving, & Winnowing.
- Special techniques like :-
- Evaporation :- A mixture of salt and water or sugar and water.
- Centrifugation :- Butter from curd, Fine mud particles suspended in water.
- Decantation (Using separating funnel) :- Oil and water.
- Sublimation :- Camphor from salt,
- Chromatography :- Different pigments from an extract of flower petals.
- Distillation and fractional distillation :- Separated components of Petroleum.
- Magnetic Separation :- Iron pins from sand.
- The amount of solute present in a given amount (mass or volume) of solution.
- Concentration of a solution = (Amount of solute)/(Amount of solvent) OR (Amount of Solute)/(Amount of solution)
- The concentration of a solution can be expressed as mass by mass percentage or as mass by volume percentage.
- Mass by mass percentage of a solution
- Mass by volume percentage of a solution
(5). Types of Solutions :-
(a) On the basis of size of solute particles :-
Colloidal solution is a heterogeneous mixture. It consists of two phases :-
- Dispersed phase :- component present in small proportion
- Dispersion medium :- component present in large proportion
The particles of colloid are large enough to scatter a beam of light passing through it and make its path visible. Thus, they show Tyndall effect. The colloidal particles are moving at random in a zigzag motion in all directions. This type of zig-zag motion of colloidal particles is called Brownian movement.
(b) On the basis of amount of solute:-
- Unsaturated solution :- A solution which has lesser amount of solute that it can dissolve at a given temperature is known as unsaturated solution.
- Saturated Solution :- A solution which has maximum amount of solute that it can dissolve at a given temperature is known as saturated solution.
- Supersaturated solution :- A solution which can dissolve amount of solute by increasing temperature saturated solution is known as supersaturated solution.
- Aqueous solution :- The solution in which the solvent is water is known as aqueous solution.
- Non-Aqueous solution :- The solution in which the solvent is other than water (ether, alcohol or acetone) known as non-aqueous solution.
(6). Physical & Chemical Changes :-
(a) Physical changes :- Changes that do not result in the production of a new substance.
- If you melt a block of ice, you still have H2O at the end of the change.
- If you break a bottle, you still have glass.
(b) Chemical changes :- Changes that result in the production of another substance.
- As in the case of autumn leaves, a change in color is a clue to indicate a chemical change.
- A half eaten apple that turns brown.
A material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal .
- These cannot be separated into their components by physical methods.
- However, these are considered as mixture because these show the properties of its constituents and can have variable composition.
- Aluminium alloys are extensively used in the production of automotive engine parts.
- Copper alloys have excellent electrical and thermal performance, good corrosion resistance, high ductility and relatively low cost.
- Stainless steel alloys are used for many commercial applications such as watch straps, cutlery etc.
- Titanium alloys have high strength, toughness and stiffness & are used in aerospace structures.
