Mixture and substance

Mixture - consists of two or more pure substances. The mixtures have variable chemical composition, not expressed by a formula.

Some mixtures are so important that they have their own names. Examples are:

- gasoline - mixture of hydrocarbons, which are substances formed by hydrogen and carbon.
- atmospheric air - a mixture of 78% nitrogen, 21% oxygen, 1% argon and other gases such as carbon dioxide.
- hydrated alcohol - 96% mixture of ethyl alcohol plus 4% water.

Substance It is each of the species of matter that constitutes the universe. It can be simple or compound.

System and phases

System It is a part of the universe that one wishes to observe, to analyze. For example: a test tube with water, a piece of iron, a mixture of water and gasoline, etc.

Stages - is the uniform visual appearance.

The mixtures may contain one or more phases.

Homogeneous mixture

It consists of only one phase. You cannot differentiate the substance. Examples:

- water + salt
- water + ethyl alcohol
- water + acetone
- water + sugar
- water + mineral salts

Heterogeneous Mixture

It is formed by two or more phases. Substances can be differentiated with the naked eye or under the microscope. Examples:

- water + oil
- granite
- water + sulfur
- water + sand + oil

Single-phase systems are homogeneous mixtures. Polyphase systems are heterogeneous mixtures.

Homogeneous systems, when formed by two or more miscible (mingling) substances, are called solutions. Examples of solutions are: salt water, vinegar, hydrated alcohol.

Heterogeneous systems can be formed by a single substance, but in several phases of aggregation (physical states). Example:

- net
- solid (ice)
- steam