1. Physical Nature of Matter & States

Everything in the universe that has mass and occupies space is called Matter. Matter is made up of tiny particles with intermolecular space and attractive forces between them.

• Solid: Fixed shape and volume, high density, negligible compressibility.
• Liquid: Fixed volume, no fixed shape, fluid, moderate compressibility.
• Gas: Neither fixed shape nor volume, high kinetic energy, highly compressible.

2. Latent Heat & Evaporation

Latent Heat: The hidden heat energy required to change the state of a substance without changing its temperature.

• Latent Heat of Fusion: Heat needed to convert 1 kg of solid into liquid at atmospheric pressure at its melting point.
• Latent Heat of Vaporisation: Heat required to convert 1 kg of liquid into gas at its boiling point.
• Evaporation: Surface phenomenon causing cooling. Rate increases with surface area, temperature, and wind speed, but decreases with humidity.

1. Pure Substances vs Mixtures

Pure Substance: Consists of a single type of particle (e.g., pure Gold, Water).

Mixture: Contains two or more pure substances mixed physically.

• Homogeneous Mixture: Uniform composition throughout (e.g., Salt in water).
• Heterogeneous Mixture: Non-uniform composition (e.g., Sand in water, Oil & Water).

2. True Solutions, Colloids & Suspensions

• Solution: Homogeneous, particle size < 1 nm, does not scatter light.
• Colloid: Heterogeneous appearance but stable, particle size 1-100 nm, exhibits Tyndall Effect.
• Suspension: Heterogeneous, particle size > 100 nm, unstable, particles settle down.

1. Laws of Chemical Combination

Law of Conservation of Mass: Mass can neither be created nor destroyed in a chemical reaction. (Lavoisier)

Law of Constant Proportions: In a chemical substance, elements are always present in definite proportions by mass. (Proust)

2. Mole Concept & Formulae

1 Mole = 6.022 × 10²³ particles (Avogadro Constant $N_A$).

Number of moles (n) = Given Mass (m) / Molar Mass (M)

Number of moles (n) = Given Particles (N) / 6.022 × 10²³

1. Subatomic Particles & Models

• Electrons (e^-): Discovered by J.J. Thomson (Cathode Rays).
• Protons (p⁺): Discovered by E. Goldstein (Anode Rays).
• Neutrons (n⁰): Discovered by J. Chadwick (Neutral particle in nucleus).
• Rutherford Model: Alpha particle scattering experiment proved nucleus existence.
• Bohr's Model: Electrons revolve in discrete energy orbits (K, L, M, N) without radiating energy.

2. Electronic Distribution & Isotopes

Bohr-Bury Scheme: Maximum electrons in nth shell = $2n^2$. K shell = 2, L shell = 8, M shell = 18.

Valency: Combining capacity of an atom determined by outermost shell electrons.

Isotopes: Same Atomic Number (Z), Different Mass Number (A) (e.g., Protium, Deuterium, Tritium).

Isobars: Same Mass Number (A), Different Atomic Number (Z) (e.g., Calcium and Argon both have A=40).