What is a pure substance ? With example plz( 3 marks )

In chemistry a substance is a form of matter, it can be a solid, a liquid or a gas. Even elements, compounds and mixtures come under the category of substance. And, a pure substance will contain same type of particles, without any impurity. So, a pure substance can be an element or a compound.

• Pure substances

  • Fixed composition
  • Constituents cannot be separated by simple physical methods.
  • Elements contain only one type of particles ? atoms (example Na, K, Cu, C, Ag) or molecules [Example: H₂, N₂, O₂, F₂]
  • Compounds are formed by the combination of two or more atoms of different elements. [Example: water (H₂O), carbon dioxide (CO₂)]
  • Constituents of compounds cannot be separated by physical methods; they can be separated by chemical methods only.