Particles

Pure and impure substances

Pure substances

Pure elements - cannot be separated e. g oxygen, hydrogen, iron.

Pure compounds - very difficult to separate e.g carbon dioxide, water, methane.

• Compounds are formed through chemical reactions and have a fixed ratio of elements.

Impure substances

Mixture - easier to separate e. g air, blood, sea water

• Mixtures can be either homogeneous (uniform composition) or heterogeneous (non-uniform composition).

Dissolving

When a solute becomes evenly disperced throughout a solvent, we say it is dissolved. Some substances dissolve easier than others.

• The rate of dissolving can be affected by temperature, stirring, and the size of solute particles.

Solute - substance dissolving

Solvent - liquid the solute dissolves in

Solution - solute dissolved in a solvent

• The concentration of a solution is the amount of solute present in a given amount of solvent or solution.

Brownian motion

This is the random movement of particles in a fluid, due to colliding with particles in the surrounding medium