This document discusses classifying different types of matter. It defines matter as anything that has mass and takes up space. Pure substances are made of only one type of matter and have consistent properties, while mixtures contain two or more substances mixed together. Pure substances are classified as either elements, which contain only one type of atom, or compounds, which are made of two or more simpler substances combined chemically. Mixtures can be either heterogeneous, with distinct parts visible throughout, or homogeneous, appearing uniform throughout.