Mixtures
We know that matter can be classified according to physical classification or
chemical classification. Chemical classification is again divided into pure
substances and mixtures.
Most of the matter we encounter consists of mixtures of different
substances. Each substance in a mixture retains its own chemical identity and
hence its own properties. Whereas pure substances have fixed compositions, the
compositions of mixtures can vary. A cup of sweetened coffee, for example, can
contain either a little sugar or a lot. The substances making up a mixture (such
as sugar and water) are called components of the mixture.
Mixtures are again divided into homogeneous mixture and Heterogeneous
mixture.
Heterogeneous mixture:
Some mixtures, such as sand, rocks, and wood, do not have the same
composition, properties, and appearance throughout the mixture. Such mixtures
are heterogeneous.
This is close-up photo is of malachite, a copper mineral, an example of
heterogeneous mixture.
Homogenous mixture:
Mixtures that are uniform throughout are homogeneous. Air is a
homogeneous mixture of the gaseous substances nitrogen, oxygen, and smaller
amounts of other substances. The nitrogen in air has all the properties that pure
nitrogen does because both the pure substance and the mixture contain the same
nitrogen molecules. Salt, sugar, and many other substances dissolve in water to
form homogeneous mixtures. Homogeneous mixtures are also called solutions.
Copper sulphate an example of homogenous mixture, it dissolves in water to
form a solution.
This blue solid shown in the photo (copper sulphate), dissolve in water to form
solutions.