Is matter really divided in two categories? 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?
Matter....

Matter is generally categorized as either mixtures or pure substances.  Pure substances are elements or compounds.  Mixtures are either heterogeneous or homogeneous.  For heterogeneous mixtures one should be easily able to discern the different components, while if the mixture is homogeneous it appears uniform.  Solutions and alloys are homogeneous mixtures.

A concept map which I give to my students: https://c7chemistry.wikispaces.com/file/view/CW%20matter%20concept%20map%20new%20rev%20091211.pdf/300804074/CW%20matter%20concept%20map%20new%20rev%20091211.pdf