1. A pure substance is a form of matter that has a constant composition and properties that are constant throughout the sample. Mixtures are physical combinations of two or more elements and/or compounds. Mixtures can be classified as homogeneous or heterogeneous.

2. Common properties of pure substances include: temperature, pressure, volume, mass, density, specific volume, energy, enthalpy, and entropy. These properties can be categorized as either extensive or intensive.

3.

Set of Properties

A pure substance is a form of matter that has a constant composition (meaning it's the same everywhere) and properties that are constant throughout the sample (meaning there is only one set of properties such as melting point, color, boiling point, etc. throughout the matter).

Appearance

A pure substance is usually all one color. The exception is if the matter has unusual optical properties, such that it reflects or refracts light. A pure substance has the same appearance and properties, no matter where you sample it. If you magnify the matter, it should appear the same everywhere in its composition.

Melting Point

Melting point, temperature at which the solid and liquid forms of a pure substance can exist in equilibrium. As heat is applied to a solid, its temperature will increase until the melting point is reached. More heat then will convert the solid into a liquid with no temperature change.

Boiling Point

The boiling point of a pure substance is the temperature at which the substance transitions from a liquid to the gaseous phase. At this point, the vapor pressure of the liquid is equal to the applied pressure on the liquid. The boiling point at a pressure of 1 atmosphere is called the normal boiling point.