📘 Chapter 2: Is Matter Around Us Pure?

Pure substance

A substance with only one kind of particle

Mixture

Made of two or more substances mixed together

Homogeneous mixture

Uniform composition (e.g. salt in water)

Heterogeneous mixture

Non-uniform composition (e.g. sand in water)

Solution

Homogeneous mixture of solute and solvent

Solute

The substance that dissolves

Solvent

The medium in which solute dissolves

Properties of solution

Cannot be filtered, stable, no Tyndall effect

Concentration

Amount of solute present in solution

Dilute solution

Less solute

Concentrated solution

More solute

Saturated solution

No more solute dissolves at given temperature

Solubility

Amount of solute that can dissolve at a temperature

Suspension

Heterogeneous mixture with visible particles

Properties of suspension

Scatters light, particles settle, can be filtered

Colloid

Heterogeneous mixture appearing homogeneous

Tyndall effect

Scattering of light by colloidal particles

Components of colloid

Dispersed phase and dispersion medium

Examples of colloids

Milk, smoke, fog, foam, gels

Physical change

No new substance formed, reversible

Chemical change

New substance formed, irreversible

Examples of physical change

Melting, boiling, dissolving

Examples of chemical change

Burning, rusting, curdling of milk

Alloy

Mixture of metals, considered a mixture

Air

Homogeneous mixture of gases