Ch 5States of Matter — Solids and Gases — Class 11 Chemistry, concept-first.

Matter around us commonly exists in three physical states — solid, liquid and gas — and this chapter builds a quantitative picture of the two extremes, the solid state and the gaseous state, starting…

Solids are further divided into two categories based on the degree of order in the arrangement of their constituent particles: crystalline solids and amorphous solids.

To describe the internal, geometric arrangement of particles in a crystalline solid precisely, chemists use the idea of a crystal lattice.

A unit cell's corners, faces, edges and body-centre are not private to that one cell — most of these positions are shared with neighbouring unit cells in the stacked lattice, so an atom sitting there…

Packing efficiency is the percentage of a unit cell's total volume that is actually occupied by its constituent atoms, treated as hard, touching spheres of equal size.

Packing efficiency tells us what fraction of a unit cell is occupied by atoms, but chemists more often need the crystal's actual, measurable density — the mass per unit volume, usually in .

No real crystal is a perfect, infinitely repeating lattice — at any temperature above absolute zero, thermal vibration and the practical realities of crystal growth introduce localised irregularities…

Having built a picture of ordered solids, the chapter now turns to the opposite extreme of molecular organisation — the gaseous state, where particles are in constant, chaotic motion with almost no fi…

Long before the kinetic theory explained why gases behave as they do, three empirical laws — discovered from careful experimental measurement — described how they behave.

Boyle's law ( at constant ), Charles's law ( at constant ), and Avogadro's law ( at constant ) can each be combined into a single proportionality: Introducing a proportionality constant , called the u…

The ideal gas equation, as introduced so far, applies to a single, pure gas. Dalton's law of partial pressures extends the same idea to a mixture of two or more gases that do not chemically react with…

Graham's law of diffusion describes how quickly different gases spread out and mix — diffusion — or escape through a tiny pinhole into a vacuum — effusion.

The ideal gas equation, , describes real gases only approximately — and the approximation breaks down noticeably at high pressure and low temperature.

Every real gas has a characteristic temperature, called its critical temperature (), above which it is physically impossible to liquefy the gas by applying pressure alone, no matter how great that pre…

This chapter examined two states of matter that sit at opposite extremes of molecular organisation, yet are explained by the same underlying idea: the microscopic arrangement and motion of particles d…

Sample papers and previous-year board questions for this subject.