Chemistry: Matter, Mixtures, and Separation - Classification and Particulate Nature of Matter

Matter is defined as anything that has mass and occupies space. It is composed of tiny, discrete particles (atoms, molecules, or ions) that are in constant motion.

The Kinetic Molecular Theory states that the speed and spacing of particles depend on their energy. In a Solid, particles are closely packed in a regular lattice; in a Liquid, they are close but can flow; in a Gas, they are far apart and move randomly at high speeds.

A Pure Substance consists of only one type of particle. This includes Elements (composed of one type of atom, like $Au$ or $O_2$) and Compounds (different atoms chemically bonded in fixed ratios, like $H_2O$ or $NaCl$).

A Mixture contains two or more substances physically blended but not chemically joined. Homogeneous mixtures (solutions) have a uniform composition (e.g., salt dissolved in water), whereas Heterogeneous mixtures have distinct phases (e.g., sand in water).

Phase Changes occur when thermal energy is added or removed, changing the $KE$ (Kinetic Energy) of particles. For instance, sublimation is the direct change from solid to gas ($S \rightarrow G$).

Separation Techniques leverage physical properties: filtration for insoluble solids, evaporation/distillation for boiling point differences, and chromatography for solubility differences.