Matter
Matter is the general term for the material things around us; we can define it as
whatever occupies space and can be perceived by our senses.
Pure Substance
Every material has its own properties. The properties of materials can be used to
classify them into general categories. Every material is made of a pure substance or
a mixture of substances. A pure substance is a type of matter with a fixed
composition. A substance can be either an element or a compound. Some
substances you might recognize are helium, aluminum, water, and salt.
Elements
You know that atoms make up the matter around you, from stars to steel to
chocolate and ice-cream. Given alI these various materials, you might think that
there must be many different kinds of atoms. But the number of different kinds of
atoms is surprisingly small. The great variety of substances results from the many
ways in which a few kinds of atoms can be combined. Just as the three colors red,
green, and blue can be combined to form any color on a television screen, or just as
the 26 letters of the alphabet make up all the words in a dictionary, only a few
kinds of atoms combine in different ways to produce all of the countless substances
in the universe. To date, we know of 115 distinct kinds of atoms. Of these, about
Course: General Science and Environment, Department of International Business, Course Number
IB-110
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90 are found in nature. The remaining kinds of atoms have been created in the
laboratory. Any material that is made up of only one type of atom is classified
as an element. Pure gold, for example, is an element. it contains only gold atoms.
Nitrogen gas is an element because it contains only nitrogen atoms. Likewise, the
graphite in your pencil is an element made from carbon. Graphite is made up solely
of carbon atoms.
Compounds
When two or more different elements combine, the substance formed is called a
compound. A compound is a pure substance in which the atoms of two or more
elements are combined in a fixed proportion. For example, water is a compound
in which two atoms of the element hydrogen combine with one atom of the
element oxygen. Chalk contains calcium, carbon, and oxygen in the proportion of
one atom each of calcium and carbon to three atoms of oxygen.
Molecules
A particle consisting of two or more atoms that are bonded together is called a
molecule. Oxygen in the air, as an example, is a diatomic (two-atom) molecule. A
molecule is a basic unit of a molecular compound. The simple sugars you eat; the
proteins in your body; and the wool and cotton fibers in your clothes all consist of
molecules formed from bonded atoms.
Mixtures
Most of the materials around us are mixtures. A mixture is a material that can be
separated by physical means into two or more substances. Unlike a pure
compound, a mixture has variable composition. When you dissolve sodium
chloride in water, you obtain a mixture; its composition depends on the relative
amount of sodium chloride dissolved. You can separate the mixture by the physical
process of distillation. Mixtures are classified into two types.
A heterogeneous mixture is a mixture that consists of physically distinct parts,
each with different properties. Following figure shows a heterogeneous mixture of
potassium dichromate and iron filings. Another example is salt and sugar that have
been stirred together. If you were to look closely, you would see the separate
crystals of sugar and salt.
Course: General Science and Environment, Department of International Business, Course Number
IB-110
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A homogeneous mixture (also known as a solution) is a mixture that is uniform
in its properties throughout given samples. When sodium chloride is dissolved in
water, you obtain a homogeneous mixture, or solution. Air is a gaseous solution,
principally of two elementary substances, nitrogen and oxygen, which are
physically mixed but not chemically combined .
States of Matter
Commonly, a given kind of matter exists in different physical forms under
different conditions. Gases, liquids and solids are all made up of microscopic
particles, but the behaviors of these particles differ in the three phases.
Note that:


Particles in a:
o gas are well separated with no regular arrangement.
o liquid are close together with no regular arrangement.
o solid are tightly packed, usually in a regular pattern.
Particles in a:
o gas vibrate and move freely at high speeds.
o liquid vibrate, move about, and slide past each other.
o solid vibrate (jiggle) but generally do not move from place to place.
Liquids and solids are often referred to as condensed phases because the particles
are very close together. Liquids and gases are often referred to as fluids.
Course: General Science and Environment, Department of International Business, Course Number
IB-110
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The following table summarizes properties of gases, liquids, and solids and
identifies the microscopic behavior responsible for each property.
Some Characteristics of Gases, Liquids and Solids and the
Microscopic Explanation for the Behavior
gas
liquid
solid
assumes the shape and
volume of its container
particles can move past
one another
assumes the shape of
the part of the
container which it
occupies
particles can
move/slide past one
retains a fixed volume
and shape
rigid - particles locked
into place
Course: General Science and Environment, Department of International Business, Course Number
IB-110
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another
compressible
lots of free space
between particles
not easily
compressible
little free space
between particles
not easily
compressible
little free space
between particles
flows easily
particles can move past
one another
flows easily
particles can
move/slide past one
another
does not flow easily
rigid - particles cannot
move/slide past one
another
Properties of Matter
Just as you use several adjectives to describe someone (color of hair or eyes, how
tall or short, etc.) several properties, or characteristics, must be used in
combination to adequately describe a kind of matter. Simply saying that something
is a colorless liquid isn't enough to identify it as water. The following chart shows
the differences between the two kinds of properties, chemical and physical, as well
as how the two kinds of physical properties, intensive and extensive, differ.
Physical Properties:
1. Extensive Properties: Depend on the amount. For example, mass, volume, length
and shape
2. Intensive Properties: Do not depend on the amount. Color, taste, melting point,
boiling point, density, temperature, pressure
Chemical Properties: How does the substance react in the presence of air, an acid,
water and bases and other chemicals? What happens if it is heated?
Course: General Science and Environment, Department of International Business, Course Number
IB-110
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