As anything that exists in nature whether living or non-living, large or small, is formed of matter and the matter is anything that occupies space, possesses mass and can be perceived by our visual or other senses. In terms of its structural organization, we also know that matter on the earth exists at three grading levels respectively called as sub-atomic, atomic and molecular in ascending order. The lowest sub-atomic level is the ultimate particulate unit of the matter below which level, the matter does not exist on the earth neither that the independent subatomic units of the matter exist as such on the earth. Although, an atom by nature is an electrically neutral species, but it lacks an independent existence on earth. Therefore, the present matter of the earth invariably has atoms found either in a group of two or more after remaining bounded through specialized chemical bonds formed between the bonded atoms inter-se either by mutual sharing or donation or transferring of electrons by the one to the other atom that all depends upon the number of the electrons present in a particular joining or combining atom in its outermost shell and thus, have formed the 3^rd level of the matter called as molecules.

Kinds of the matter: As what we have seen above that the chemical combination of different atoms either of the same kind or different results into the formation of molecules. Thus, on the basis of this chemical combination or organization, the matter on the earth predominantly exists in 3 forms or categories respectively called as elements, compounds and mixtures.

While an element is formed by the combination of similar atoms and each element is noted for having its own specific properties of colour, taste or chemical reactivity.

A compound on the other hand, is formed by the combination of two or more, but always different types of atoms. If the said two or more different atoms are combined together through covalent bonds, the resulting compound is called as molecular and if the joined atoms are joined through electrovalent or ionic bonds, the said compound is described as the ionic compound as such. For example, in this context, water (H2O) is an example of a molecular compound and NaCl of an ionic compound.

A mixture as a form of the matter has its basis in the fact that on the present earth there is hardly anything that can be called as a pure compound such that most of the earth’s matter exists as a mixture either of two or more than two compounds. In terms of their physical state, the mixtures may also be found as solids, liquids or gases for that matter. Of these mixtures however, it is the fluid mixtures that are of common sight around us in which one part of the liquid acts as the solvent that generally is larger in concentration and the other component dissolved in the solvent that may be a solid or liquid and is lesser in concentration as compared to the solvent is called as a solute.

ALL fluid mixtures may exist in one of the following three forms:

True solutions: A true solution also called as a crystalloid solution is generally homogenous in nature in the sense that there is a uniform concentration of solute particles at all levels of this solution. Its homogenous nature is also ascribed to the fact that its solute particles smaller than 0.001 microns in size and thus, are invisible even under the microscope. Solutions of the nature of salt or sugar are some of the best examples of the so called true solutions.

Suspensions: In a suspension, the solute particles are in the nature of molecular aggregates such that they are somewhere larger than 0.1 micron in size and are thus, visible even by naked eyes. Say for example, by mixing up flour or clay particles in water, the kind of fluid mixture, we may obtain is called a suspension.

Emulsion: A suspension in which both solvent and solute are liquids is called as an emulsion. For example, butter is an emulsion of “ghee” in water.

Colloids: A colloid mixture is the one that lies somewhere in-between the true solution and a suspension. Its solute particles or molecules are characterized for being larger in size so called as macromolecules that measure 0.001 micron to 0.1 micron in size or diameter. Owing to this much of the size of solute molecules, they remain non-diffusible and can be visible under an ultra microscope only. Colloidal mixtures are also heterogeneous in nature and are represented by the substances or mixtures such as milk, gum, gelatin or egg albumen etc. These colloidal mixtures are also noted for coagulation upon heating. The table drawn below shows the size of solute particles of the different mixtures: