Page 1 of almost every Textbook start with the ordinary divison of matter in 2 categories: Substances and Mixtures.
Substances, or Pure Substances sometimes, are defined
as a form of matter that has constant chemical composition and characteristic properties.It cannot be separated into components by physical separation method.
This is according to Wikipedia, at least.
Mixtures always citing wikipedia, instead are
materials made up of two or more different substances which are mixed but are not combined chemically.... Mixtures are one product of a mechanical blending or mixing chemical substances such as elements and compounds, without chemical bonding or other chemical change, so that each ingredient substance retains its own chemical properties and makeup.
Is this separation so radical?
Is there something in between? What about alloys?