Matter
MATTER
What is matter?
Matter
is simply anything that has mass and takes up space.
Knowing this, we realize that
almost everything in the universe is made up of matter. Examples of matter include the plants and
animals around us, the food we eat, the water we drink and even the air we
breathe. Man himself is matter.
The mass of an object is the quantity
of matter an object contains and is the same everywhere measured in moles. For
practical purpose, mass is measured in kilograms with a weighing balance.
In general, matter is built up of one or
more of the following elementary particle; atom, molecules and ions.
Four phases of matter
Solid:
A
solid is matter in which the molecules are very close together and
cannot move around. Examples of solids include rocks, wood, and ice
(frozen water). Liquid:
A liquid is matter in which the molecules are close together and move around slowly. Examples of liquids include drinking water, mercury at room temperature, and lava (molten rock).
Gas:
Plasma:
Properties of matter
Substances can be identified by the characteristics they
possess. These characteristics are called properties.
Sugar is a white solid which dissolves in water and tastes
sweet, while iron has a metallic lustre; it may be magnetized and rusts with
the formation of a reddish deposit.
PHYSICAL AND CHEMICAL CHANGES IN MATTER
Matter undergoes changes. These changes may be temporary and
easily reversible or they may be permanent and very difficult to reverse. The
former is known as a physical change and the latter as a chemical change. Continue reading to learn more about them.
PHYSICAL CHANGES
A Physical change is one which is easily
reversed and in which no new substances are formed.
A change in the state of a
substance is a physical property of matter.
The dissolution of common salt in water is a physical change because no
new substances are formed and the salt can easily be recovered from the
solution.
Forward reaction (Mixing) salt + water (solute solvent) → salt
solution (solution)
Reverse reaction (Evaporation) salt solution (solution) → salt
+ water (solute solvent)
The magnetization and demagnetization
of iron rods can also be seen as a physical change of matter as no new
substances are formed.
CHEMICAL CHANGES
A Chemical change is one which is not easily
reversed and in which new substances are formed.
A piece of wood burns with a flame, giving out heat and
light. As it burns, the wood slowly disappears until only a little ash is left.
This is a chemical change as we cannot reverse the process to get back the
firewood. Burning of substances is a chemical change.
Wood →ash + gases
Some more examples of chemical changes
include;
·
The rusting of iron
·
The addition of water to quicklime, i.e. the
slaking of lime.
·
Fermentation and decay of substance.
·
The changes in an electrochemical cell.
Comparing the
characteristics
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PHYSICAL CHANGE
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CHEMICAL CHANGE
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·
It is easily reversible
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·
It is not easily reversible
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·
No new substances are formed
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·
Entirely new substances are always produced.
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·
There is no change in the mass of a substance
involved in such a changed
|
·
There is a change in the mass of a substance
that undergoes such a change.
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ELEMENTS, COMPOUNDS AND MIXTURES
Matter may be classified into elements, compounds and
mixtures. An element or a compound
cannot be separated into more than one component by physical methods, which
makes it a pure substance. While a
mixture consists of more than one element and/or compound. The components of a
mixture can be separated by physical methods.
Most elements
and compounds are not pure. They contain small amounts of other substances
known as impurities. Such impure elements and compounds can also be regarded as
mixture.
Element
An element is a substance
which cannot be split into simpler units by an ordinary chemical process.
Hundreds of elements which
include familiar substances like gold, tin, iron, iodine and oxygen, as well as
unfamiliar ones like actinium, xenon and rubidium have been discovered by
Scientists. These elements can be found in the Earth’s crust, in the air and in
the sea.
Elements constitute
the building units of all other substances, these substances which are built up
of elements are known as compounds.
There are over a
hundred known elements, Ninety of which are said to occur naturally; the rest
are made in the lab (artificial). Abbreviations and symbols are used to
represent elements, e.g. “O” for oxygen and “H” for hydrogen.
Elements can
be grouped in the form of a Periodic Table (shown below). There are six types
of elements; the reactive metals, transition metals,
lanthanides and actinides, pure metals, non-metals and noble gases. more
commonly, elements are grouped as metals, semi-metals or metalloids and
non-metals.
COMPOUNDS
A compound is a substance
which contains two or more elements chemically combined.
It is formed as a result of a chemical change. It is a new
substance with entirely different properties.
Example. Water is a compound formed as a result of a
chemical reaction between the component elements, hydrogen and oxygen, in the
ratio of 2:1 respectively.
MIXTURES
A mixture contains two or
more constituents which can easily be separated by physical methods.
The constituents of mixture can be elements or compounds, or
both. The constituents may also be present in different proportions. The
constituents of a mixture retain their individual identities because their
physical and chemical properties are not changed by simple mixing. Many
familiar things around us are mixtures.
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