Pure Substance: Pure substances are defined as substances that are made of only one type of atom, or only one type of molecule.
NaCl with no iodine is a pure substance, but ordinary table salt is not a pure substance.
Element: A class of substances that cannot be separated into simpler substances by chemical means.
Silicon is made up of sand, quartz, rock crystal, amethyst, agate, flint and opal. Since silicon has all of these in it they can be broken down into simpler substances, and that is why it's an element.
Compound: A thing that is composed of two or more separate elements.
The organic compounds in coal are composed of the elements carbon, hydrogen, oxygen, nitrogen, and sulfur.
Mixture: A substance made by mixing other substances together.
A tossed salad is a mixture because everything in the salad can be separated and put back to its original state.
Homogeneous Mixture: A mixture which has uniform composition and properties throughout.
Blood plasma contains many things, but it is a homogeneous suspension. A homogeneous mixture is simply any mixture that is uniform in composition throughout. Blood plasma is a homogeneous mixture.
Heterogeneous Mixture: A mixture is a combination of two or more pure substances in which the original substances retain there chemical properties.
Solutions: A liquid mixture in which the minor component is uniformly distributed within the major component.
NaCl in water is a solution.
Suspension: A suspension is a heterogeneous mixture in which solute-like particles settle out of a solvent-like phase some time after their introduction. We apply the word 'suspension' when particles are big enough to eventually settle. If the particles are too small to ever settle, they are said to form a colloid.
colloid: A homogeneous, noncrystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, sols, and emulsions; the particles do not settle and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.