Some Basic concepts in Chemistry

Nature of Matter and Dalton's Atomic Theory

Nature of Matter :

Substance : A substance is a form of matter that has distinct properties and definite composition.

Properties : Extensive → depend upon the amount
Intensive → Independent of the amount.

Hygroscopic nature :
The tendency of substance to absorb moisture from atmosphere is known as hygroscopic nature
eg : Anhydrous CuSO4

Deliquescence :
The solid substance with appreciable amount of moisture on exposing to atmosphere to pass in solution state.
eg : NaOH , KOH

Efflorescence :
The hydrated substance which lose their water of crystallization completely or partly on exposing to air.
eg : FeSO4.7H2O ;  Na2SO4.10H2O

Dalton's Atomic Theory :

Postulates :

  • Atom is an indivisible particle.
  • Atoms of different elements combine in fixed ratio to form compounds.
  • Atoms are neither created nor destroyed.
  • The formation of new compounds results from the rearrangement of existing atoms.

Drawbacks :

  • It couldn't explain why do atoms combine to form a molecule.
  • It couldn't explain the nature of forces.
  • It couldn't explain the Gay-Lussac's law.
  • It couldn't explain that, why should atoms of an element differ in their masses.

View the Topic in this Video from 0:13 to 5:45

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