Particles

Pure substances

Materials that have a fixed composition and distinct properties.

Pure elements

Elements that cannot be separated into simpler substances, e.g., oxygen, hydrogen, iron.

Pure compounds

Chemical substances that consist of two or more elements bonded together, difficult to separate, e.g., carbon dioxide, water, methane.

Impure substances

Materials that contain two or more different substances and can vary in composition.

Mixture

A combination of two or more substances where each retains its individual properties and is easier to separate, e.g., air, blood, sea water.

Dissolving

The process when a solute becomes evenly dispersed throughout a solvent.

Solute

The substance that is dissolved in a solution.

Solvent

The liquid in which a solute is dissolved to form a solution.

Solution

A homogeneous mixture formed by the dissolution of a solute in a solvent.

Brownian motion

The random movement of particles in a fluid resulting from collisions with nearby particles.