Properties and Separation of Chemical Mixtures

Properties and Classification of Mixtures

A mixture is the aggregation of matter of two or more substances that meet the following conditions:

• a) The characteristic properties of the components are not altered.
• b) The amount or proportion of each component can be variable.
• c) The components can be separated by physical methods (evaporation, filtration, magnetism, etc.).

Homogeneous and Heterogeneous Mixtures

A mixture is homogeneous when its components cannot be distinguished at a glance because it has the same appearance throughout. A mixture is heterogeneous when the components can be appreciated by the naked eye.

Physical and Chemical Processes

In a physical process, there are no alterations to the substances that intervene. For example, filtration and evaporation are physical processes. A compound substance is a type of matter whose components do not conserve their characteristic properties, and to separate them, it is necessary to apply chemical processes. Other substances are produced from simpler ones, differently from a mixture. When a chemical process occurs, new chemical substances are produced. For example, combustion and electrolysis are chemical processes.

Simple Substances and the Nature of Matter

A simple substance is the kind of matter that is not made of others. For example, hydrogen and oxygen cannot be decomposed or separated into other substances by physical methods or by chemical methods. It can be concluded that matter is the result of the union or connection of simple substances to form composite substances or mixture substances (simple and/or composite).

Common Separation Techniques

Filtration: Use when one substance is liquid and the other is in fine powder form or solid grains. A funnel with filter paper is used so that the fluid passes through the pores of the paper, but the solid particles cannot.

Settling (Decantation): Used for two or more liquid components. Place the liquid mixture to be separated in a funnel and let it stand until it separates into layers, with the lower density liquid being higher, while the densest is at the bottom. The key (stopcock) that the funnel bears at the bottom allows for separate extraction.

Crystallization: Used to separate a dissolved solid in a liquid (solvent).

Distillation: Used to separate a homogeneous mixture of two or more liquids. The resulting liquid is the distillate.

Solubility and Volume Equivalents

Solubility is the maximum amount of solute that can dissolve in 100 g of solvent at a given temperature. 1 liter is equivalent to a volume of 1 dm³.