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Chapter- 2 Is Matter Around Us ""PURE""?

                ASM..Knowledge & education
                          ( By. Ghanshyam kr. Chaudhary)
Chapter2: Is matter around us pure..?



Pure: It means a substance free from foreign particle or mixing of any substance such as solid, liquid & gas.But accordind to scientific language all things  are  mixture  of  so many substances, not of single one. 
That’s why they  are  not  pure. 
 Example:
 Milk, water, fat, etc. 

Substance  :
It is defined as a kind of matter that cannot be separated into other kind of matter by any physical process.

  • Pure substances means that all elements have same chemical properties. 
  • A pure substance is made up of same kind of elements.
Qus(1): What is a mixture? write their type and define them with suitable example?
Ans: mixture is defined as anything where two or more  substances (element or compound) are simply mixed  together in any proportion is called mixture
 Examples :  
The air is a mixture of oxygen, nitrogen, argon, carbon dioxide and water vapour.

There are two types of Mixture : 
 (i) Homogenous mixture,
(ii) Heterogenous mixture.

Homogenous mixture:
It is a type of mixture by which two or more substance are completely mixed together with same proportion of their mass.
Example: Sugar  in  water, it is complete mixture of two different substance.

Heterogenous mixture:
It is a type of mixture by which two or more sunstance are not mixed properly with each other the substance are partly separated from each other.
Example: mixture of sand in water.
Qus(2): Defined solution with example?
Ans: Solution is a homogeneous mixture of two or more substance.
Example: sugar solution of water. It is a type of solution where sugar is completely dissolved in water hence it is homogenous mixture.
Solution is made up of two component 
solute or solvent.
Solute: Substance which is dissolve and normally it is present in small amount.

Solvent: substance in which solute is dissolved.
example: water it is a type of solvent where sugar particle is dissolved.

Qus(3) : write the types of solution?With suitable example?Ans: There are three type of solution:
  • True solution, 
  • Colloidal solution,
  • Suspension solution


Part B

Method of Separation of Mixtures:
There are various method apply to separate a mixture, these are as follows:







CRYSTALLISATION:-To remove impurities from a mixture or given substance is first dissolving in suitable solvent and crystallising out one component by the application of heat. eg. (1) Purification of salt from sea water.
(2) Separation of crystals(i.e potash alum from there impure crystals.

Qus(4) : Write the basic difference between chemical and physical change with suitable example of each?
Ans: Chemical Changes
  •  Not easily reversed
  •  New product(s) formed
  •  Reactants used up 
  •  Often heat/light/sound/fizzing occurs 
  •  Electricity may be produced
  •   A precipitate  may  form 
  •   E.g., Wood burning 

Physical Changes
  •  Easily reversible
  •   No new products 
  •  Often just a state change
  • electricity may not produced
  • No precipitate is formed
  • E.g., ice melting.       
Qus(5) : write the difference between Mixture and compound?
Ans:


Law of Constant Proportion:

According  to  this  law, “A  pure  chemical  compound  always  contain  the  same  elements Which combines together in the same proportion by their mass irrespective  of  the fact from where the sample has been taken or from which procedure has  it been produced.
Example: H20( water) the composition of hyodrogen and oxygen is always 1:8

Law of Conservation of Mass :
According to this law, “Mass can neither be created nor destroyed.
During a chemical reaction  total  mass of reactants will also equal to total mass of the product formed.
 for example,
 mA + mB --> mAB
where mA & mB is mass of reactant
and mAB is mass of product.
(Note: explained in chapter 3 atoms and molecules)

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                                    ।। Bolna Padega ।।
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