MATTER
Science interprets nature in terms of energy and matter. Matter, the material of which the universe is composed, may be defined as anything that has mass and occupies space. Mass is a measure of quantity of matter.
The mass of a body which is determined by means of an analytical balance is invariable, while the weight of a body is not. Weight is the gravitational force of attraction exerted by the earth on a body. The weight of a given body varies with the distance of that body from the centre of the earth. The weight of a body is directly proportional to its mass as well as the earth’s gravitational attraction.
Matter exists in three physical states which are gas, liquid and solid. A gas maintains neither volume nor shape; but completely fills any container which it is introduced and may be expanded or compressed within relatively wide limits. A liquid has no fixed shape, but assumes the shape of the container only within the limit of the volume it occupies (definite volume). Volumes of liquids do not vary greatly with changes in temperature and pressure. A solid, under any ordinary condition, maintains definite volume and shape. Observed variations in the volume of solids with changes in temperature and pressure are very small. All matter can change from one state to another when heated or cooled. An example is water.
PROPERTIES OF MATTER
A matter may be characterised by its intrinsic properties, i.e ., attributes that distinguish it from all other types of matter. Properties such as density, colour, physical state, melting point, hardness and electrical conductivity are known as physical properties because they can be observed without causing any change in the chemical composition of the matter.
The chemical properties of matter are those that describe the chemical changes (chemical reactions) that matter undergoes. For example, the rusting of iron. Properties that are not characteristics of any particular type of matter, such as mass, length and temperature are known as extrinsic properties.
A distinct portion of matter that is uniform throughout in composition and in intrinsic properties is called a phase. If a material consists of only one phase, it is said to be homogeneous matter. If it consists of more than one phase, it is classified as heterogeneous matter. Iron, copper, salt and a solution of salt in water are examples of homogeneous matter, while wood, granite, concrete, and a mixture of ice and water are examples of heterogeneous matter, while wood granite, concrete, and a mixture of ice and water are examples of heterogeneous matter.
The phases of heterogeneous matter have distinct boundaries and are usually easily discernible. In graphite, for example, it is possible to identify pink feldspar crystals, colourless quartz crystals and shiny black mica crystals. Thus, graphite is said to consist of three phases.
A mixture may be homogeneous or heterogeneous. Homogeneous mixtures are called solution and the single phase in which a solution occurs may be gaseous, liquid or solid. A solution is made up of more than one substance, one being uniformly dispersed in the other.
Each phase of a heterogeneous mixture has its own properties. A homogeneous mixture has a single set of intrinsic properties, but each of these properties depends on the composition of the mixture. The density, taste, boiling point and electrical conductivity, for example, of aqueous salts solutions vary with the proportions of salt and water present. Pure substances are homogeneous materials that have fixed compositions and invariable intrinsic properties.
There are two types of pure substance namely:
- An element: This is a pure substances that cannot be decomposed into any simpler pure substance.
- A compound: This is a pure substance that is composed of two elements in a fixed and definite proportion. The preparation of a compound from the constituent element is known as synthesis, while element is called analysis.
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