There are some important terms that are often used; I thought it is good to define them so that their meaning is clear :

Process

The term process is used to indicate any action or operation, natural or man-made that results into change.

Examples:

  • Heating and cooling an object are processes that result into change of temperature of the object.
  • Corrosion is a natural process that results into change of the nature of a metal object.
  • Evaporation and Vaporization of water are two processes which consist in changing the state of water, i.e. from liquid water into vapor.
  • The process of mixing salt and water produces an aqueous solution of salt.

Mixture

This term is used in the text to designate a situation where two or more substances have been mixed together, without expecting a chemical reaction. Only that in the mixture some salts may be dissociated into their ions.

Examples:

  • Mixing water and sugar
  • Mixing sugar, salt and sand

To Mix/Mixing

This verb will be used to designate the action of putting two or more substances together in a container, shaking or stirring them, either expecting a chemical reaction or not (see examples above)

Homogeneous Mixture/Solution

A homogeneous mixture also called solution is mixture in which the different component in the mixture cannot be differentiated or distinguished by ordinary means of observation.

When liquid, homogeneous mixtures are habitually called solutions and are transparent, i.e. light can pass through.

Heterogeneous mixture

A heterogeneous mixture is the mixture where the different components can be observed by ordinary means of observation. A heterogeneous mixture is not transparent, it is opaque.