a mixture is a substance made up of other substances.

differences: mixtures are very different from substances because they are a mixture of different things, pure substances arent, they are only one type of atom.

The definition of a heterogeneous mixture is any mixture that is not fitted into in composition.

The definition of a homogenous mixture is a mixture that has the same appearance, and composition throughout.

Pure substances are substances that are made of only one type of atom or only one type of molecule.