Basic Concepts of Chemistry - JEE Main & Advanced

1. Matter and Its Classification

1.1 States of Matter

  • Solid: Definite shape and volume
  • Liquid: Definite volume but no fixed shape
  • Gas: Neither definite shape nor volume
  • Plasma: Ionized state of matter at high temperatures
  • BEC (Bose-Einstein Condensate): State at extremely low temperatures

1.2 Classification of Matter

Pure Substances Mixtures
  • Elements (Metals, Non-metals, Metalloids)
  • Compounds (Organic, Inorganic)
  • Homogeneous (Solutions)
  • Heterogeneous (Colloids, Suspensions)

Practice Questions (JEE Level)

Question 1:

The ratio of radii of second orbit of He⁺ to the first orbit of H atom is:

(a) 1:2 (b) 2:1 (c) 1:4 (d) 4:1

Answer: (b) 2:1

Question 2:

Which of the following has the highest electron affinity?

(a) F (b) Cl (c) Br (d) I

Answer: (b) Cl (Fluorine has lower EA than Cl due to small size and electron repulsion)

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