Matter—Properties and Change: Basic Concepts
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Properties of Matter—Substances
Matter that has a uniform and
unchanging composition is called
a substance, also known as a
pure substance.
Table salt is a substance.
Another example of a pure
substance is water.
Water is always composed
of hydrogen and oxygen.
Matter—Properties and Change: Basic Concepts
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Properties of Matter—Substances
• Seawater, on the other hand, is not a
substance because samples taken from
different locations will probably have
differing compositions.
Matter—Properties and Change: Basic Concepts
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Physical Properties of Matter
• A physical property is a characteristic that
can be observed or measured without
changing the sample’s composition. Physical
properties describe pure substances, too.
• Because substances have uniform and
unchanging compositions, they have consistent
and unchanging physical properties as well.
Matter—Properties and Change: Basic Concepts
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Physical Properties of Matter
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Matter—Properties and Change: Basic Concepts
Topic
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Physical Properties of Matter
• density,
• taste,
• color,
• hardness,
• odor,
• melting point,
• and boiling point are common physical
properties that scientists record as identifying
characteristics of a substance.
Matter—Properties and Change: Basic Concepts
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Extensive and Intensive Properties
• Physical properties can be further
described as being one of two types.
• Extensive properties are
dependent upon the amount of
substance present. Mass is an
extensive property.
• Length and volume are also
extensive properties.
Matter—Properties and Change: Basic Concepts
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Extensive and Intensive Properties
• Intensive properties are independent of the
amount of substance present.
• For example, the density of a substance is the
same no matter how much substance is
present.
Matter—Properties and Change: Basic Concepts
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Chemical Properties of Matter
• The ability of a substance to combine with or
change into one or more other substances is
called a chemical property.
• The ability of iron to form rust when
combined with air is an example of a
chemical property of iron
• The fact that iron does not undergo a change in
the presence of nitrogen is another chemical
property of iron.
Matter—Properties and Change: Basic Concepts
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Observing Properties of Matter
• Every substance has its own unique set of
physical and chemical properties.
Matter—Properties and Change: Basic Concepts
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States of Matter
• In fact, all matter that exists on Earth can be
classified as one of these physical forms
called states of matter.
• Scientists recognize a fourth state of matter
called plasma, but it does not occur naturally
on Earth except in the form of lightning bolts.
Matter—Properties and Change: Basic Concepts
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States of Matter
• The physical state of a substance is a physical
property of that substance.
• Each of the three common states of matter
can be distinguished by the way it fills a
container.
Matter—Properties and Change: Basic Concepts
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Solids
• A solid is a form of
matter that has its
own definite shape
and volume.
• Wood, iron, paper,
and sugar are
examples of solids.
Matter—Properties and Change: Basic Concepts
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Solids
• The particles of matter
in a solid are very
tightly packed; when
heated, a solid expands,
but only slightly.
• A solid does not
conform to the shape
of the container in
which it is placed.
Matter—Properties and Change: Basic Concepts
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Liquids
• A liquid is a form of matter that flows, has
constant volume, and takes the shape of its
container.
• Common examples of liquids include water,
blood, and mercury.
• The particles in a liquid are not rigidly held
in place and are less closely packed than are
the particles in a solid: liquid particles are
able to move past each other.
Matter—Properties and Change: Basic Concepts
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Liquids
• This allows a
liquid to flow and
take the shape of
its container,
although it may
not completely
fill the container.
Matter—Properties and Change: Basic Concepts
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Liquids
• Because of the way
the particles of a
liquid are packed,
liquids are virtually
incompressible.
Like solids, liquids
tend to expand
when heated.
Matter—Properties and Change: Basic Concepts
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Gases
• A gas is a form of matter that flows to
conform to the shape of its container and fills
the entire volume of its container.
• Compared to solids and liquids, the particles
of gases are very far apart.
• Because of the significant amount of space
between particles, gases are easily
compressed.
Matter—Properties and Change: Basic Concepts
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Gases
• The word gas refers to a
substance that is naturally
in the gaseous state at room
temperature.
Matter—Properties and Change: Basic Concepts
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Gases
• The fact that substances can change form is
another important concept in chemistry
• The state of matter is a physical property.
Matter—Properties and Change: Basic Concepts
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Matter—Properties and Change: Basic Concepts
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Physical Changes
• A substance often undergoes changes that
result in a dramatically different appearance
yet leave the composition of the substance
unchanged.
• Changes such as this, which alter a substance
without changing its composition, are known
as physical changes.
Matter—Properties and Change: Basic Concepts
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Physical Changes
• Melting and formation of a gas are both
physical changes and phase changes.
• When you encounter
terms such as boil,
freeze, condense,
vaporize, or melt in
your study of chemistry,
the meaning generally
refers to a phase change
in matter.
Matter—Properties and Change: Basic Concepts
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Chemical Changes
• Chemical properties relate to the ability of a
substance to combine with or change into one
or more substances.
• A process that involves one or more
substances changing into new substances is
called a chemical change, which is
commonly referred to as a chemical
reaction.
Matter—Properties and Change: Basic Concepts
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Chemical Changes
• The new
substances formed
in the reaction
have different
compositions and
different properties
from the
substances present
before the reaction
occurred.
Matter—Properties and Change: Basic Concepts
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Chemical Changes
• Rust is a chemical combination of iron and
oxygen.
• In chemical
reactions, the
starting substances
are called reactants
and the new
substances that are
formed are called
products.
Matter—Properties and Change: Basic Concepts
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Chemical Changes
• Thus iron and oxygen are reactants and rust
is a product.
• When you encounter terms such as explode,
rust, oxidize, corrode, tarnish, ferment, burn,
or rot, the meaning generally refers to a
chemical reaction in which reactant
substances produce different product
substances.
Matter—Properties and Change: Basic Concepts
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Conservation of Mass
• By carefully measuring mass before and after
many chemical reactions, it was observed
that, although chemical changes occurred, the
total mass involved in the reaction remained
constant.
• The constancy of mass in chemical reactions
was observed so often that scientists assumed
the phenomenon must be true for all
reactions.
Matter—Properties and Change: Basic Concepts
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Conservation of Mass
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Matter—Properties and Change: Basic Concepts
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Conservation of Mass
• The law of conservation of mass states that
mass is neither created nor destroyed during a
chemical reaction—it is conserved.
• The law of conservation of mass is one of the
most fundamental concepts of chemistry.
Matter—Properties and Change: Basic Concepts
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Conservation of Mass
• The equation form of the law of conservation
of mass is:
Matter—Properties and Change: Additional Concepts
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Mixtures
• A mixture is a combination of two or more
pure substances in which each pure substance
retains its individual chemical properties.
• The composition of mixtures is variable, and
the number of mixtures that can be created by
combining substances is infinite.
Matter—Properties and Change: Additional Concepts
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Mixtures
• Although much of the focus of chemistry is
the behavior of substances, it is important to
remember that most everyday matter occurs
as mixtures.
• Substances tend naturally to mix; it is
difficult to keep things pure.
Matter—Properties and Change: Additional Concepts
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Types of Mixtures
• Mixtures themselves are classified as either
heterogeneous or homogeneous.
• A heterogeneous mixture is one that does
not blend smoothly throughout and in which
the individual substances remain distinct.
• The sand and water mixture is an example of
a heterogeneous mixture.
Matter—Properties and Change: Additional Concepts
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Types of Mixtures
• Suppose you draw a drop from the top of a
mixture of sand and water using an
eyedropper.
• The drop would be almost completely water.
Matter—Properties and Change: Additional Concepts
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Types of Mixtures
• If you draw a second drop from the bottom
of the mixture, that drop would contain
mostly sand.
• Thus the composition of the sand–water
mixture is not uniform—the substances have
not blended smoothly and the two substances
of the mixture (sand on the bottom and water
on the top) remain distinct.
Matter—Properties and Change: Additional Concepts
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Types of Mixtures
• A homogeneous mixture has constant
composition throughout; it always has a
single phase.
• Let’s examine a salt–water mixture using the
eyedropper.
• Every drop of the mixture contains the same
relative amounts of salt and water.
Matter—Properties and Change: Additional Concepts
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Types of Mixtures
• Homogeneous
mixtures are also
referred to as
solutions.
Matter—Properties and Change: Additional Concepts
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Types of Mixtures
• Solutions may contain solids, liquids, or gases,
Matter—Properties and Change: Additional Concepts
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Types of Mixtures
• The solid–solid solution
is called an alloy. (ex
steel)
Matter—Properties and Change: Additional Concepts
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Separating Mixtures
• Most matter exists naturally as mixtures.
• Because the substances in a mixture are
physically combined, the processes used to
separate a mixture are based on differences in
physical properties of the substances.
Matter—Properties and Change: Additional Concepts
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Separating Mixtures
• Filtration is
a technique
that uses a
porous barrier
to separate a
solid from a
liquid.
Matter—Properties and Change: Additional Concepts
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Separating Mixtures
• Most homogeneous mixtures can be
separated by distillation
• Distillation is a separation technique that is
based on differences in the boiling points of
the substances involved.
Matter—Properties and Change: Additional Concepts
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Separating Mixtures
• Crystallization is a separation technique that
results in the formation of pure solid particles
of a substance from a solution containing the
dissolved substance.
Matter—Properties and Change: Additional Concepts
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Separating Mixtures
• Chromatography is a technique that
separates the components of a mixture on the
basis of their tendency to be drawn across the
surface of another material.
• The separation occurs because the various
components of the ink spread through the
paper ant different rates.
Matter—Properties and Change: Additional Concepts
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Elements
• An element is a pure substance that cannot
be separated into simpler substances by
physical or chemical means.
Matter—Properties and Change: Additional Concepts
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Elements
• Each element
has a unique
chemical name
and symbol.
• The chemical symbol consists of one, two, or
three letters; the first letter is always
capitalized and the remaining letter(s) are
always lowercase.
Matter—Properties and Change: Additional Concepts
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Elements
• As new elements were being discovered
chemists began to see patterns of similarities
in the properties of sets of elements.
• In 1869, the Russian chemist Dmitri
Mendeleev devised the chart which organized
all of the known elements into rows and
columns based on their similarities and their
masses.
Matter—Properties and Change: Additional Concepts
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Elements
• Mendeleev’s organizational table was the
first version of the periodic table of elements.
• The periodic table organizes the elements
into a grid of horizontal rows called periods
and vertical columns called groups or
families.
Matter—Properties and Change: Additional Concepts
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Elements
• Elements in the same group have similar
chemical and physical properties.
• The table is called “periodic” because the
pattern of similar properties repeats as you
move from period to period.
Matter—Properties and Change: Additional Concepts
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Periodic Table
Matter—Properties and Change: Additional Concepts
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Compounds
• A compound is a combination of two or
more different elements that are combined
chemically.
• Most of the substances that
you are familiar with are
compounds.
• Water, table salt, table sugar,
and aspirin are examples of
common compounds.
Matter—Properties and Change: Additional Concepts
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Categories of Matter
Matter—Properties and Change: Additional Concepts
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Compounds
• The chemical symbols of the periodic table
make it easy to write the formulas for
chemical compounds.
• For example, table salt, or sodium chloride, is
composed of one part sodium (Na) and one
part chlorine (Cl), and its chemical formula is
NaCl.
• Water is composed of two parts hydrogen (H)
to one part oxygen (O), and its formula is
H2O.
Matter—Properties and Change: Additional Concepts
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Compounds
• Unlike elements, compounds can be broken
down into simpler substances by chemical
means.
• In general, compounds that naturally occur
are more stable than the individual
component elements.
Matter—Properties and Change: Additional Concepts
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Compounds
• The properties of a compound are different
from those of its component elements.
Matter—Properties and Change: Additional Concepts
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Law of Definite Proportions
• An important characteristic of compounds is
that the elements comprising them combine
in definite proportions by mass.
• This observation is so fundamental that it is
summarized as the law of definite
proportions.
• This law states that, regardless of the amount,
a compound is always composed of the same
elements in the same proportion by mass.
Matter—Properties and Change: Additional Concepts
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Law of Definite Proportions
• The mass of the compound is equal to the
sum of the masses of the elements that make
up the compound.
• The ratio of the mass of each element to the
total mass of the compound is a percentage
called the percent by mass.
Matter—Properties and Change: Additional Concepts
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Law of Multiple Proportions
• The law of multiple proportions states that
different compounds can be formed by a
combination of the same elements. The
elements are combined in different ratios.
• Ratios compare the relative amounts of any
items or substances.
Matter—Properties and Change: Additional Concepts
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Law of Multiple Proportions
• Hydrogen peroxide is composed of two parts
hydrogen and two parts oxygen. (2:2)
• Hydrogen peroxide differs from water in that
it has twice as much oxygen.
• When we compare the mass of oxygen in
hydrogen peroxide to the mass of oxygen in
water, we get the ratio 2:1.