What is Matter :
Everything that is around us and the presence of which can be felt with the help of any of our five senses, i.e., sight, touch, smell, hearing, and taste, is called matter; in fact, this whole universe is made up of only two things, viz., matter and energy. Experience has shown that all types of matter possess mass and occupy space. Hence,
Matter is defined as any thing that occupies space, possesses mass and the presence of which can be felt by any one or more of our five senses.
The example of the matter is innumerable. These include clothes, iron, gold, plastics, wood, water, petrol, oil, air, etc.
Classification of Matter :
There are two ways of classifying matter :
(A) Physical Classification
(B) Chemical Classification
(A) Physical classification. Based on the physical state under the ordinary condition of temperature and pressure, the matter is classified into the following three types :
1. Solid
2. Liquids
3. Gases
They differ from each other in the packing of their constituent particles. In a solid, the constituent particles are very closely packed in an orderly fashion, and there is not much freedom of movement (except vibratory motion). Hence, they possess a definite shape and a definite volume.
In a liquid, the particles are comparatively less close to each other and, therefore, they can move around. Hence, they have a definite volume but no definite shape. In gas, the particles are far apart and therefore have much greater freedom of movement. Hence, they possess neither definite volume nor definite shape. Based on these characteristics, the three states of matter may be defined as follows :
- A substance is said to be solid if it possesses a definite volume and a definite shape, e.g., sugar, iron, gold, wood, etc.
- A substance is said to be liquid, if it possesses a definite volume but no definite shape. They take up the shape of the vessel in which they are put, e.g., water, milk, oil, mercury, alcohol, etc.
- A substance is said to be gaseous if it neither possesses a definite volume nor a definite shape. This is because they fill up the whole vessel in which they are put, e.g., hydrogen, oxygen, carbon dioxide, air, etc.
Difference between gas and vapor. Vapour represents a gaseous state of a substance that is liquid at room temperature. A substance that is in a gaseous state at room temperature is called a gas but not vapor. For example, ammonia is gas (not vapor), but water on heating forms water vapors.
(B) Chemical Classification. Broadly speaking, all kinds of matter may be classified into two types:
(1) Homogeneous and
(2) Heterogeneous.
The word 'material' is commonly used for all kinds of matter, whether homogeneous or heterogeneous.
A matterial is said to be homogeneous if it has uniform composition and identical properties throughout.
since any distinct portion of matter that is uniform throughout in composition and properties is called a "phase," hence,
A material is said to be homogeneous, if it consists of only one phase. On the other hand, a material is said to be heterogeneous if it consists of a number of phases.
The composition of each phase is uniform throughout itself but is quite different from those of the other phases. The different phases are separated from each other by distinct boundaries. For example, water, iron, salt, a solution of salt in water, air (which contains several gases), motor oil (which contains several hydrocarbons), etc., are homogeneous. In contrast, a mixture of ice and water, salt and sand, iron and sulfur, etc., are heterogeneous.
However, a more scientific way of classification, called the 'chemical classification of matter,' is briefly described :
All types of materials are believed to be made up of "substances." A material containing only one substance is called a "pure substance." On the other hand, materials containing more than one substance are not pure and are called "mixtures." Pure substances are further classified into two types, called "Elements" and "Compounds." Mixtures are also of two types, namely "Homogeneous mixture" and "Heterogeneous mixtures." Pure substances (i.e., elements and compounds) are always homogeneous. Homogeneous mixtures are also called "solutions." The single-phase in which a solution occurs may be gaseous, liquid, or solid. Air, salt dissolved in water, and brass (an alloy of copper and zinc) are examples of gaseous, liquid, and solid solutions, respectively.
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