Mixtures and Solutions

A mixture is formed when two or more substances are combined but are NOT chemically joined. Each substance keeps its own properties and the mixture can usually be separated by physical means. Examples include trail mix, sand and pebbles, and a salad.

Mixtures

• Components keep their individual properties — each substance stays the same.
• Can be separated by physical methods such as sieving, filtering, or picking apart.
• The amounts mixed do not have to follow a fixed ratio.
• Examples: trail mix, iron filings and sand, gravel and water.

Solutions

• A solution is a special mixture where one substance dissolves completely in another.
• The result looks uniform — you cannot see the separate particles.
• Solute: the substance that dissolves (e.g. salt, sugar).
• Solvent: the substance in which the solute dissolves (e.g. water).
• Solubility: how well a substance dissolves in a given solvent.
• Examples: salt water, sugar in tea, copper sulphate in water.

Separation Methods

• Filtration — passes a mixture through a filter to remove insoluble solids (e.g. muddy water).
• Evaporation — heats a solution until the solvent evaporates, leaving the dissolved solute behind (e.g. recovering salt from salt water).
• Sieving — separates solid mixtures by particle size (e.g. sand and pebbles).
• Magnetism — attracts iron or steel particles out of a mixture (e.g. iron filings from sand).