An atom is the smallest existing chemical particle with an equal number of protons and electrons, and as a result has no charge. Each atom is a chemical element, which can react with each other to form compounds or physically combine to make a mixture.
A compound is a substance formed by the chemical union of two or more chemical elements, with a definite, unchanging ratio. It has its own properties, different from the properties of its parts, and requires chemical reactions to be separated.
A mixture is made from different substances that are not chemically bonded. Each of the substances within a mixture retains its own properties, and the ratio is not fixed. The substances are easily physically separated.
Methods of separation include:
Filtration: Separating insoluble particles from a liquid
Passing a mixture through a filter funnel.
Evaporation: Removing liquid from a solution
Heating a solution to boiling point until the liquid is gone.
Chromatography: Separating controlled substances or dyes
Placing dots on chromatography paper and letting it run up the paper with capillary action.
Distillation: Separating liquids from each other. Simple - two liquids. Fractional - many liquids, involving a fractionating column.
Boiling and condensing liquids of different boiling temperatures.
Chemical particles disperse through a fluid through diffusion and dilution. Diffusion is the net movement of particles from an area of high concentration to an area of low concentration.
This can be demonstrated using experiments between hydrochloric acid and ammonia, or bromine in a glass cylinder, as well as by placing food dye in water. The dispersal of particles can be seen through the experiments described here (specification)
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