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•has mass
•occupies space
•Exists in three states: solid, liquid, and gas
•rigid shape
•fixed volume and shape
•very little volume change as
temperature and pressure change
•properties determined by
arrangement of particles
•only slightly compressible
•definite volume but no
specific shape
•assumes the shape of its
container
•fluid
•well-defined surface
•only slightly compressible
•no fixed volume or shape
•takes on the shape and
volume of its container
•highly compressible
•volume varies according to
temperature and pressure
Matter can be classified into mixtures and pure
substances.
•A pure substance is one with constant composition.
•The composition of a pure substance is always the same,
regardless of its source.
•Example: all samples of water contain the same
proportions by mass of hydrogen and oxygen.
•Pure substances contain compounds (combinations of
elements) or free elements.
Substance with a constant
composition that can be broken
down into elements by chemical
processes.
Example: sodium chloride (NaCl)
commonly called table salt
•Elements are substances that cannot be broken
down into simpler substances by chemical or
physical means.
•Sodium, chlorine, iron, lead, copper, and
aluminum are all common examples of elements.
•Most matter consists of mixtures of pure substances.
•Examples: wood, gasoline, wine, soil, and air
•Mixtures have variable composition.
•Two types: homogeneous and heterogeneous
•visibly indistinguishable parts
•same properties throughout
•also called solutions
•Examples: salt dissolved in water,
brass, and air
•visibly distinguishable parts
•consists of two or more regions called phases that differ in
properties
•Examples: pizza, chicken noodle soup, ice cubes in water
•Mixtures can be separated into pure substances by physical
methods.
1. Distillation: a process that depends on the differences
in the volatility (how readily substances become gases)
of the components.
In simple distillation, a mixture is heated in a device and the most
volatile component vaporizes (turns into gas) at the lowest
temperature, and the vapor (gas) passes through a cooled tube (a
condenser) where it condenses back into the liquid state.
2. Filtration: used when a mixture consists of a liquid and a
solid.
The mixture is poured onto a mesh, such as filter paper,
which passes the liquid and leaves the solid behind.
3. Chromatography: general name applied to a series of
methods that employ a system with two phases (states)
of matter: a mobile phase and a stationary phase.
The stationary phase is a solid, and the mobile phase is
either a liquid or a gas.
The separation occurs because the components of a mixture
have different affinities for the two phases and thus move at
different rates.
A component with a high
affinity for the mobile phase
moves quickly.
A component with a high
affinity for the solid phase
moves more slowly.
•Paper chromatography: employs a strip of porous paper,
such as filter paper, for the stationary phase.
A line of the mixture
to be separated is
placed at one end of a
sheet of porous paper
(stationary phase).
The paper is dipped
into a liquid (the
mobile phase).
The paper acts as a
wick to draw up the
liquid.
The component with
the weakest
attraction for the
paper travels faster
than the
components that
cling to the paper.
•A physical property is one that can be observed without
changing the chemical makeup of a substance.
•Examples: mass, volume, boiling temperature, melting
temperature, color, and conductivity.
•Extensive properties: properties that depend on sample
size. In other words, a property that changes when the size
of the sample changes.
•Examples: mass, volume, weight, and length.
•Intensive properties: properties that are independent of
sample size. In other words, a property that doesn’t change
when you take away some of the sample.
•Examples: color, electrical conductivity, density, hardness,
melting point, and boiling point.
•A physical change is a change in the form of a substance,
not in its composition.
•When water freezes or boils, its changes its state but
remains water; it is still composed of H2O molecules.
•Examples: melting, boiling, grinding, and pounding into
sheets.
•A chemical property describes a chemical change (chemical
reaction) that a substance undergoes. In other words, how a
substance interacts with other substances.
•Examples: flammability (the ability to catch on fire), toxicity
(the ability to be poisonous), and oxidation (the ability to
react with oxygen; which causes apple slices to turn brown
and iron to rust).
•A chemical change is one in which a given substance
becomes a new substance or substances with different
properties and different composition.
•Examples: combustion (burning), cooking an egg, rusting
of an iron pan, and mixing hydrochloric acid and sodium
hydroxide to form water and a salt.
The element mercury
(top left) combines with
the element iodine (top
right) to form the
compound mercuric
iodide (bottom).