Is Matter Around Us Pure – Comprehensive Bullet-Point Notes

Element

A pure substance that cannot be split into two or more simpler substances by any chemical process.

Compound

Pure substances made of two or more elements chemically combined in a definite ratio, with properties differing from constituent elements and fixed melting/boiling points.

Mixture (Impure Substance)

Physical combinations of two or more elements and/or compounds in any proportion, where constituents retain their original properties and can be separated by physical methods.

Homogeneous Mixture

A mixture with uniform composition throughout, like sugar in water or air.

Heterogeneous Mixture

A mixture with non-uniform composition, like sand and sugar or water and oil.

Solution (True Solution)

A homogeneous mixture of two or more substances in a single phase, with particle size < $1\,\text{nm}$ that do not scatter light.

Solvent

The component present in a larger amount in a solution.

Solute

The component present in a smaller amount in a solution.

Alloys

Mixtures of two or more metals or a metal with a non-metal, considered mixtures due to variable composition and retention of constituent properties.

Solubility

The amount of solute present in a saturated solution at a given temperature.

Saturated Solution

A solution in which no additional solute dissolves at the given temperature.

Suspension

Heterogeneous mixtures with visible particles > $100\,\text{nm}$ that settle on standing, can be separated by filtration, and scatter light.

Colloid (Colloidal Solution)

Heterogeneous mixtures with particle size between $1\,\text{nm}$ and $100\,\text{nm}$, which scatter light (Tyndall effect) but do not settle under gravity.

Dispersed Phase

The colloidal particles (solute-like) in a colloid.

Dispersion Medium

The continuous phase (solvent-like) in a colloid.

Tyndall Effect

The phenomenon of light scattering by colloidal or very fine suspension particles, making the path of the light beam visible.

Centrifugation

A separation method where rapid spinning forces denser particles to the bottom (sediment).

Separating Funnel

A separation method used for immiscible liquids with different densities, forming distinct layers.

Evaporation

A separation method for a volatile solvent from a non-volatile solute.

Sublimation

A separation method for sublimable solids from non-sublimable impurities.

Chromatography

A separation method based on differential adsorption and solubility of components on/in a stationary and mobile phase.

Simple Distillation

A separation method for two miscible liquids with a large boiling point difference ($\ge 25\,\text{K}$) that do not decompose.

Fractional Distillation

A separation method for miscible liquids with a boiling point difference < $25\,\text{K}$ or for multiple liquids, using a fractionating column.

Crystallization

A purification method for solids by forming crystals after partial evaporation or cooling of a hot saturated solution.

Physical Change

A change that alters physical properties (state, color, hardness, density, M.P., B.P.) without forming new substances, usually reversible.

Chemical Change

A change that produces one or more new substances with different chemical properties (odor, combustibility, reactivity), generally irreversible and involving significant energy change.