Characteristics and nature of matter - WAEC TUTORIALS
Nature
Matter is anything that has mass and occupy space (Volume). All matter is made
of atoms composed of protons, neutrons, and electrons. The center, or nucleus,
of the
atom is composed of positively charge protons and neutral neutrons with negative electron revolving round it. The outside of the atom has negatively charged electrons in various orbits.
atom is composed of positively charge protons and neutral neutrons with negative electron revolving round it. The outside of the atom has negatively charged electrons in various orbits.
Properties
A property is any
characteristic of matter which can be detected or measured, and can be used to
identify or describe the matter. Properties can be of two types – physical
properties and chemical properties.
A substance is
matter which can be identified by a fixed set of properties.
A physical property
of matter can be determined without carrying out any chemical reaction on it.
Thus, for example, properties
like colour of gold or the boiling point of water are physical properties.
A chemical property
of matter is determined only when the matter reacts with another kind of matter
and converts to a third kind. Thus, a new shiny iron nail reacts with oxygen in
air over time to form a layer of brown rust covering the nail. This reaction of
iron with oxygen is one of its chemical properties.
Properties can also
be classified as being qualitative or quantitative. Qualitative properties are
those which can only be described and cannot be measured and expressed
numerically, such as the colour of gold. Quantitative properties can be measured
and expressed numerically, such as the boiling point of water, which is 100°C.
Yet another
classification of properties is into extensive properties and intensive
properties. Extensive properties depend on the amount of matter present, such
as the mass or the volume of a sample. Intensive properties do not depend upon
the amount of matter, such as density and freezing point. Incidentally, all
chemical properties are intensive properties.
Each substance has
its own unique set of properties which differentiate it from other substances.
Classification
There are two major categories
of classification of matter which are physical classification and chemical
classification. The image below depicts the classification of matter into the two major
categories, and the sub-classifications therein.
Physical Classification
This classification
divides matter into three categories – solids, liquids,
and gases – known as the three states (or phases) of
matter.
States of Matter
Solids are matter having fixed shape, fixed volume and are
almost impossible to compress. Of course, solids can be crushed into powder
form (in which case the fixed shape is destroyed), but in essence the powder
still remains a solid.
Solids are composed
of particles which are very near to each other because of mutual forces of
attraction, and thus in some kind of order. The particles' movement is limited
to vibrating in the positions they are in. see image below .
Image: Solid particles
If energy is added to the solid in
the form of heat, the particles gain more kinetic energy and move farther from each other.
Solids can occur in
two forms. Crystalline solids are made up of crystals.
Amorphous solids have no such small units and hence their internal structure
is shapeless.
Liquid
Liquids are matter having a fixed volume but no fixed shape like the case of solid –
they take the shape of the container. Liquids are very difficult to
compress.
Liquids are composed
of higher kinetic energy particles which overcome their mutual forces of attraction and
move independently. This is the reason why liquids do not have a fixed shape.
The particles move in straight lines until they collide with other particles
and rebound. Since the particles are a little more spread apart when compared
to solids, liquids can be compressed a little.
Image: Liquid particles
For a liquid in a
container, its top free surface consists of moving particles which are
attracted by the particles below, and do not have energy enough to overcome the
attraction. As a result, they remain within the boundary of the top surface and
cannot escape, giving the liquid the fixed volume.
Gas
Gases are matter having neither a
fixed shape nor a fixed volume. They are very easy to compress.
Gases consist of high energy particles which are so far from each other
that the forces of attraction between them become negligible. The particles can
spread out to occupy whatever space is available. Thus, gases have neither
fixed shape nor fixed volume.
Change of State
The change of state from solid to liquid is called melting or fusion,
while the reverse process is called freezing or solidification.
The melting point is the temperature at which a
substance changes from solid to liquid. Conversely, freezing point is
the temperature at which a substance changes from a liquid to solid. These two
temperatures are essentially the same – which one is used depends upon whether
the substance is being heated or being cooled.
The change of state from liquid to gas is called vaporisation or boiling,
while the reverse process is called condensation. The boiling
point is the temperature at which a substance changes from liquid to
gas. Conversely, condensing point is the temperature at which
a substance changes from a gas to liquid.
When liquids gradually turn into gases at temperatures less than their
boiling point, the process is called evaporation.
Some substances, like iodine and solid carbon
dioxide, can go directly from solid to gaseous state without melting – this
is known as sublimation. The reverse process of sublimation is
called deposition.
See diagrammatic representation below
Chemical
Classification
A chemical change involves a chemical reaction resulting
in change in chemical properties of the substance.
In any chemical change, (1) one or more substances are used up (at least
partially), (2) one or more new substances are formed, and (3) energy is
absorbed or released. The chemical properties of substances are revealed as
they undergo chemical changes.
The chemical classification scheme broadly divides matter into two
categories – pure substances and mixtures.
Pure Substances
A pure substance (or simply substance) is
matter which can be identified by a fixed set of properties, which
distinguishes it from other substances. A substance cannot be further broken
down into simpler substances by physical means (i.e. through physical changes),
although some substances can be broken down through chemical means (through
chemical changes).
Example of pure water has a fixed freezing point of 273K (0°C), a boiling
point of 373K (100°C) and a density of 1000kg/m3, irrespective of where the
sample is derived from. Such properties identify water as a unique substance,
with no other substance matching these characteristics.
Elements
An element is a pure substance which cannot be further
split up by chemical reactions into simpler substances. They are the
fundamental substances of which all matter is composed. The smallest particle
of an element of importance to chemistry is the atom.
There are 115 known elements presently, out of which only 91 occur
naturally. The remaining elements have been produced artificially by nuclear
scientists in the laboratory using particle accelerators.
To simplify the representation of elements in chemical reactions, they
are represented by symbols. Basically, the symbol of an element
refers to one atom of the element. Some symbols are derived from the latin name
of the particular elements. The names and symbols of some common elements are
listed in Table 1.
Elements may be solids, liquids or gases. At room temperatures, only mercury, bromine and francium are
liquids. Hydrogen, nitrogen, oxygen, fluorine, chlorine and
the noble gases(helium, neon, argon, xenon, krypton and radon)
are gases. The rest of the elements are solids. The Periodic Table is
a chart of elements presenting details about all of them.
Elements are further classified as metals, non-metals & metalloids or semi-metals.
About 80% of elements are metals.
Metals are elements which have “metallic”
lustres, are malleable and ductile,
are of high relative density, and are good conductors of heat and electricity.
All metals are solid except mercury, which is the only liquid metal
at room temperature.
Non-metals do not possess any of the
properties of metals. They do not have a lustre, not malleable nor ductile,
and do not have high relative density. Non-metals are solids or gases except bromine,
which is the only non-metal which is liquid at room temperature.
Metalloids (or semi-metals) are
those elements which exhibit both the properties of metals and non-metals to
some extent, such as boron and silicon.
See table below for some names of elements and their symbols
Table 1: Names
& Symbols of some common elements.
|
|
Element
|
Symbol
|
aluminium
|
Al
|
argon
|
Ar
|
barium
|
Ba
|
boron
|
B
|
bromine
|
Br
|
calcium
|
Ca
|
carbon
|
C
|
chlorine
|
Cl
|
fluorine
|
F
|
helium
|
He
|
hydrogen
|
H
|
iodine
|
I
|
lithium
|
Li
|
magnesium
|
Mg
|
manganese
|
Mn
|
nitrogen
|
N
|
oxygen
|
O
|
phosphorus
|
P
|
silicon
|
Si
|
sulphur
|
S
|
zinc
|
Zn
|
copper (cuprum)
|
Cu
|
iron (ferrum)
|
Fe
|
lead (plumbum)
|
Pb
|
mercury (hydrargyrum)
|
Hg
|
potassium (kalium)
|
K
|
silver (argentum)
|
Ag
|
sodium (natrium)
|
Na
|
Compounds
A compound is a pure substance which is formed by chemical
combination of two or more elements in a fixed ratio by mass.
Compounds are the substances which can be decomposed by chemical methods into
their constituent elements.
The smallest unit of a compound, known as a molecule, or a formula
unit, is composed of atoms of the constituent elements. A compound is
represented by a chemical formula which indicates one molecule
(formula unit) of the compound containing atoms of its elements.
The number of possible compounds is almost infinite. A chemical compound
always contains the same elements chemically combined together in a fixed
proportion by weight. A compound has properties which are very much
different from its constituent elements.
Those compounds which are composed of carbon and hydrogen,
along with other elements, are called organic compounds, as these
compounds form the basis of all life on earth. All other compounds are
categorised under the name of inorganic compounds.
(a) Water, chemically known as hydrogen monoxide,
is a compound which contains hydrogen and oxygen combined
in the ratio of 1:8 by weight. Its chemical formula is H2O.
It is a liquid which cannot catch fire, though it is made up of hydrogen,
a gas which is combustible, and oxygen, another gas which supports
combustion. Thus, the properties of water are very much
different from its constituent elements. Water can be
decomposed into hydrogen and oxygen by the
passage of electric current through it.
(b) Common salt, or sodium chloride, is a compound of sodium, a soft silvery highly reactive metal, and chlorine, a greenish poisonous gas. But common salt is non-poisonous and essential part of our diet.
(b) Common salt, or sodium chloride, is a compound of sodium, a soft silvery highly reactive metal, and chlorine, a greenish poisonous gas. But common salt is non-poisonous and essential part of our diet.
Mixtures
A mixture is a sample of matter containing two or more
pure substances physically mixed together, without any chemical
interaction, in any ratio by weight.
Since the mixture is formed by physical combination of substances, the
substances making up the mixture do not lose their individual properties. Also,
as the components of the mixture can be present in any ratio by weight, it is
possible to have mixtures in varying concentrations.
Mixtures are categorised into homogeneous and heterogeneous mixtures.
A homogeneous mixture (or a uniform mixture)
is one in which the composition is the same throughout. A homogeneous mixture
is also called a solution, and consists of a substance designated
as a solvent (the
substance present in largest amount) and other substances (one or more) as solutes.
Generally, a solvent is a liquid, while solutes can be solid, liquid or
gaseous.
A solution with water as the solvent is termed an aqueous
solution.
An alloy is a solution of two or more metals, and
generally stands for a solid solution of the metals. An alloy of mercury with
a metal is called an amalgam.
Liquids that mix together completely are called miscible liquids.
The final solution looks like a single liquid. In contrast, liquids which do
not mix completely and tend to settle down as different layers are said to be immiscible.
Soda water is an example of a homogeneous mixture or solution, in which water (a
liquid) is the solvent and carbon dioxide (a gas) is the
solute. Brass is another example (a solid solution) in which copper is
the solvent and zinc the solute.
A heterogeneous mixture (or a non-uniform
mixture) is one in which the composition varies throughout.
A rock can be classified as a heterogeneous mixture. It generally
consists of a number of mineral components distributed non-uniformly.
In any mixture, (a) the composition can be varied and (b) each component
of the mixture retains its own properties. Mixtures can be separated into
component substances by physical means because each component retains its
properties.
Table 2: Examples
of different types of mixtures.
|
||
Type of Mixture
|
Homogeneous
|
Heterogeneous
|
Solid in solid
|
alloys like
- bronze - brass - coins |
- sugar and salt
- gunpowder (charcoal, sulphur and potassium nitrate) - iron and sulphur |
Solid in liquid
|
- brine (salt in water)
- sugar solution |
- fresh precipitates in test tubes
- muddy water |
Solid in gas
|
iodine vapour in air
|
smoke (carbon particles in air)
|
Liquid in solid
|
amalgams (mercury in metals like copper, zinc etc.)
|
bromine absorbed in charcoal
|
Liquid in liquid
|
All miscible liquids like:
- water + alcohol - alcohol + benzene |
All immiscible liquids like
- oil + water - benzene + water - chloroform + water - carbon tetrachloride + water |
Liquid in gas
|
Moist air, any gas collected over water
|
Air near rivers, lakes and seas
|
Gas in solid
|
hydrogen in palladium
|
chlorine in charcoal
|
Gas in liquid
|
- Aerated water
- carbon dioxide in water |
River or lake water at different depths
|
Gas in gas
|
Air (oxygen + nitrogen + other gases)
|
A mixture is a sample of matter containing two or more
pure substances physically mixed together, without any chemical
interaction, in any ratio by weight.
Since the mixture is formed by physical combination of substances, the
substances making up the mixture do not lose their individual properties. Also,
as the components of the mixture can be present in any ratio by weight, it is
possible to have mixtures in varying concentrations.
Mixtures are categorised into homogeneous and heterogeneous mixtures.
A homogeneous mixture (or a uniform mixture)
is one in which the composition is the same throughout. A homogeneous mixture
is also called a solution, and consists of a substance designated
as a solvent (the
substance present in largest amount) and other substances (one or more) as solutes.
Generally, a solvent is a liquid, while solutes can be solid, liquid or
gaseous.
A solution with water as the solvent is termed an aqueous
solution.
An alloy is a solution of two or more metals, and
generally stands for a solid solution of the metals. An alloy of mercury with
a metal is called an amalgam.
Liquids that mix together completely are called miscible liquids.
The final solution looks like a single liquid. In contrast, liquids which do
not mix completely and tend to settle down as different layers are said to be immiscible.
Soda water is an example of a homogeneous mixture or solution, in which water (a
liquid) is the solvent and carbon dioxide (a gas) is the
solute. Brass is another example (a solid solution) in which copper is
the solvent and zinc the solute.
A heterogeneous mixture (or a non-uniform
mixture) is one in which the composition varies throughout.
A rock can be classified as a heterogeneous mixture. It generally
consists of a number of mineral components distributed non-uniformly.
In any mixture, (a) the composition can be varied and (b) each component
of the mixture retains its own properties. Mixtures can be separated into
component substances by physical means because each component retains its
properties.
Table 2: Examples
of different types of mixtures.
|
||
Type of Mixture
|
Homogeneous
|
Heterogeneous
|
Solid in solid
|
alloys like
- bronze - brass - coins |
- sugar and salt
- gunpowder (charcoal, sulphur and potassium nitrate) - iron and sulphur |
Solid in liquid
|
- brine (salt in water)
- sugar solution |
- fresh precipitates in test tubes
- muddy water |
Solid in gas
|
iodine vapour in air
|
smoke (carbon particles in air)
|
Liquid in solid
|
amalgams (mercury in metals like copper, zinc etc.)
|
bromine absorbed in charcoal
|
Liquid in liquid
|
All miscible liquids like:
- water + alcohol - alcohol + benzene |
All immiscible liquids like
- oil + water - benzene + water - chloroform + water - carbon tetrachloride + water |
Liquid in gas
|
Moist air, any gas collected over water
|
Air near rivers, lakes and seas
|
Gas in solid
|
hydrogen in palladium
|
chlorine in charcoal
|
Gas in liquid
|
- Aerated water
- carbon dioxide in water |
River or lake water at different depths
|
Gas in gas
|
Air (oxygen + nitrogen + other gases)
|
A mixture is a sample of matter containing two or more
pure substances physically mixed together, without any chemical
interaction, in any ratio by weight.
Since the mixture is formed by physical combination of substances, the
substances making up the mixture do not lose their individual properties. Also,
as the components of the mixture can be present in any ratio by weight, it is
possible to have mixtures in varying concentrations.
Mixtures are categorised into homogeneous and heterogeneous mixtures.
A homogeneous mixture (or a uniform mixture)
is one in which the composition is the same throughout. A homogeneous mixture
is also called a solution, and consists of a substance designated
as a solvent (the
substance present in largest amount) and other substances (one or more) as solutes.
Generally, a solvent is a liquid, while solutes can be solid, liquid or
gaseous.
A solution with water as the solvent is termed an aqueous
solution.
An alloy is a solution of two or more metals, and
generally stands for a solid solution of the metals. An alloy of mercury with
a metal is called an amalgam.
Liquids that mix together completely are called miscible liquids.
The final solution looks like a single liquid. In contrast, liquids which do
not mix completely and tend to settle down as different layers are said to be immiscible.
Soda water is an example of a homogeneous mixture or solution, in which water (a
liquid) is the solvent and carbon dioxide (a gas) is the
solute. Brass is another example (a solid solution) in which copper is
the solvent and zinc the solute.
A heterogeneous mixture (or a non-uniform
mixture) is one in which the composition varies throughout.
A rock can be classified as a heterogeneous mixture. It generally
consists of a number of mineral components distributed non-uniformly.
In any mixture, (a) the composition can be varied and (b) each component
of the mixture retains its own properties. Mixtures can be separated into
component substances by physical means because each component retains its
properties.
Table 2: Examples
of different types of mixtures.
|
||
Type of Mixture
|
Homogeneous
|
Heterogeneous
|
Solid in solid
|
alloys like
- bronze - brass - coins |
- sugar and salt
- gunpowder (charcoal, sulphur and potassium nitrate) - iron and sulphur |
Solid in liquid
|
- brine (salt in water)
- sugar solution |
- fresh precipitates in test tubes
- muddy water |
Solid in gas
|
iodine vapour in air
|
smoke (carbon particles in air)
|
Liquid in solid
|
amalgams (mercury in metals like copper, zinc etc.)
|
bromine absorbed in charcoal
|
Liquid in liquid
|
All miscible liquids like:
- water + alcohol - alcohol + benzene |
All immiscible liquids like
- oil + water - benzene + water - chloroform + water - carbon tetrachloride + water |
Liquid in gas
|
Moist air, any gas collected over water
|
Air near rivers, lakes and seas
|
Gas in solid
|
hydrogen in palladium
|
chlorine in charcoal
|
Gas in liquid
|
- Aerated water
- carbon dioxide in water |
River or lake water at different depths
|
Gas in gas
|
Air (oxygen + nitrogen + other gases)
|
A mixture is a sample of matter containing two or more
pure substances physically mixed together, without any chemical
interaction, in any ratio by weight.
Since the mixture is formed by physical combination of substances, the
substances making up the mixture do not lose their individual properties. Also,
as the components of the mixture can be present in any ratio by weight, it is
possible to have mixtures in varying concentrations.
Mixtures are categorised into homogeneous and heterogeneous mixtures.
A homogeneous mixture (or a uniform mixture)
is one in which the composition is the same throughout. A homogeneous mixture
is also called a solution, and consists of a substance designated
as a solvent (the
substance present in largest amount) and other substances (one or more) as solutes.
Generally, a solvent is a liquid, while solutes can be solid, liquid or
gaseous.
A solution with water as the solvent is termed an aqueous
solution.
An alloy is a solution of two or more metals, and
generally stands for a solid solution of the metals. An alloy of mercury with
a metal is called an amalgam.
Liquids that mix together completely are called miscible liquids.
The final solution looks like a single liquid. In contrast, liquids which do
not mix completely and tend to settle down as different layers are said to be immiscible.
Soda water is an example of a homogeneous mixture or solution, in which water (a
liquid) is the solvent and carbon dioxide (a gas) is the
solute. Brass is another example (a solid solution) in which copper is
the solvent and zinc the solute.
A heterogeneous mixture (or a non-uniform
mixture) is one in which the composition varies throughout.
A rock can be classified as a heterogeneous mixture. It generally
consists of a number of mineral components distributed non-uniformly.
In any mixture, (a) the composition can be varied and (b) each component
of the mixture retains its own properties. Mixtures can be separated into
component substances by physical means because each component retains its
properties.
Table 2: Examples
of different types of mixtures.
|
||
Type of Mixture
|
Homogeneous
|
Heterogeneous
|
Solid in solid
|
alloys like
- bronze - brass - coins |
- sugar and salt
- gunpowder (charcoal, sulphur and potassium nitrate) - iron and sulphur |
Solid in liquid
|
- brine (salt in water)
- sugar solution |
- fresh precipitates in test tubes
- muddy water |
Solid in gas
|
iodine vapour in air
|
smoke (carbon particles in air)
|
Liquid in solid
|
amalgams (mercury in metals like copper, zinc etc.)
|
bromine absorbed in charcoal
|
Liquid in liquid
|
All miscible liquids like:
- water + alcohol - alcohol + benzene |
All immiscible liquids like
- oil + water - benzene + water - chloroform + water - carbon tetrachloride + water |
Liquid in gas
|
Moist air, any gas collected over water
|
Air near rivers, lakes and seas
|
Gas in solid
|
hydrogen in palladium
|
chlorine in charcoal
|
Gas in liquid
|
- Aerated water
- carbon dioxide in water |
River or lake water at different depths
|
Gas in gas
|
Air (oxygen + nitrogen + other gases)
|
A mixture is a sample of matter containing two or more
pure substances physically mixed together, without any chemical
interaction, in any ratio by weight.
Since the mixture is formed by physical combination of substances, the
substances making up the mixture do not lose their individual properties. Also,
as the components of the mixture can be present in any ratio by weight, it is
possible to have mixtures in varying concentrations.
Mixtures are categorised into homogeneous and heterogeneous mixtures.
A homogeneous mixture (or a uniform mixture)
is one in which the composition is the same throughout. A homogeneous mixture
is also called a solution, and consists of a substance designated
as a solvent (the
substance present in largest amount) and other substances (one or more) as solutes.
Generally, a solvent is a liquid, while solutes can be solid, liquid or
gaseous.
A solution with water as the solvent is termed an aqueous
solution.
An alloy is a solution of two or more metals, and
generally stands for a solid solution of the metals. An alloy of mercury with
a metal is called an amalgam.
Liquids that mix together completely are called miscible liquids.
The final solution looks like a single liquid. In contrast, liquids which do
not mix completely and tend to settle down as different layers are said to be immiscible.
Soda water is an example of a homogeneous mixture or solution, in which water (a
liquid) is the solvent and carbon dioxide (a gas) is the
solute. Brass is another example (a solid solution) in which copper is
the solvent and zinc the solute.
A heterogeneous mixture (or a non-uniform
mixture) is one in which the composition varies throughout.
A rock can be classified as a heterogeneous mixture. It generally
consists of a number of mineral components distributed non-uniformly.
In any mixture, (a) the composition can be varied and (b) each component
of the mixture retains its own properties. Mixtures can be separated into
component substances by physical means because each component retains its
properties.
Table 2: Examples
of different types of mixtures.
|
||
Type of Mixture
|
Homogeneous
|
Heterogeneous
|
Solid in solid
|
alloys like
- bronze - brass - coins |
- sugar and salt
- gunpowder (charcoal, sulphur and potassium nitrate) - iron and sulphur |
Solid in liquid
|
- brine (salt in water)
- sugar solution |
- fresh precipitates in test tubes
- muddy water |
Solid in gas
|
iodine vapour in air
|
smoke (carbon particles in air)
|
Liquid in solid
|
amalgams (mercury in metals like copper, zinc etc.)
|
bromine absorbed in charcoal
|
Liquid in liquid
|
All miscible liquids like:
- water + alcohol - alcohol + benzene |
All immiscible liquids like
- oil + water - benzene + water - chloroform + water - carbon tetrachloride + water |
Liquid in gas
|
Moist air, any gas collected over water
|
Air near rivers, lakes and seas
|
Gas in solid
|
hydrogen in palladium
|
chlorine in charcoal
|
Gas in liquid
|
- Aerated water
- carbon dioxide in water |
River or lake water at different depths
|
Gas in gas
|
Air (oxygen + nitrogen + other gases)
|
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