Pure Substances and Mixtures

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Pure Substances, Elements,
Compounds, and Mixtures
What are pure substances?
PURE SUBSTANCES  Substances
made of one kind of material with a
unique set of chemical and physical
properties. Elements and
compounds are pure substances.
What is an element?
ELEMENT a
pure substance
that cannot be
broken down into
simpler
substances
There are slightly more than 100 known
chemical elements that are arranged on the
periodic table developed by Dimitri
Mendelev. Each element is abbreviated
with one or two symbols. The 1st letter is
capitalized and the 2nd is not. Each symbol
represents the English name, old name, or
Latin name of the element.
EXAMPLE:

(Latin) Aurum-Gold –Au

(English) Oxygen – O

(Old) Natrium – Sodium - Na
Some elements are named after
famous scientists, countries, states,
and planets.
 (101) Mendelevium – scientist
 (32) Germanium – Germany
 (98) Californium – California
 (92) Uranium Uranus
What are compounds?
COMPOUNDS  2 or more elements
chemically combined
EX: magnesium oxide (MgO2)
Magnesium
Oxygen
Separating Compounds
Compounds can be separated by chemical
means because they are chemically
combined. Compounds can be broken down
by electrolysis. Electrolysis literally means
“to tear apart with electricity”. It is a
technique using an electric current to pass
through a substance. If the substance is a
compound, it may be broken down into the
separate elements that form it.
EX: H2O (water)
If an electric current passes through
the compound, the compound will
break down into the two elements
hydrogen and oxygen.
What is a mixture?
MIXTURES  a blend of two or more
pure substances
Types of Mixtures


Heterogeneous Mixture  a
mixture that has visibly different
parts
Homogeneous Mixture 
mixtures that do not contain visibly
different parts
(Hetero- and Homo- are two Greek roots that
mean “different” and “same”.)
Heterogeneous vs Homogeneous
Separating Mixtures
Mixtures can be separated by:
decantation, filtration, crystallization,
distillation, chromatography.
Decantation
Decantation  gentle pouring off of a
liquid without disturbing a solid sediment
EXAMPLE:
*cleaning a fish tank and leaving behind
most of the sand, shells, and plants
* drinking coffee and leaving small residue
of coffee grounds behind in a cup
Filtration
Filtration  passage
of a liquid or gas
through a porous
substance for the
purpose of removing
suspended solids.
A mixture of water
and an insoluble
substance like sand
can be separated by
filtering.
Crystallization

Crystallization refers to the
formation of solid crystals from a
homogeneous solution. It is
essentially used as a solid-liquid
separation technique.
Distillation

Distillation  the
process in which a
liquid is evaporated
and the vapors
condensed

The solution is heated until
it boils. The liquid with the
lowest boiling point boils
first and becomes a vapor
(gas). The vapor is cooled
in the condenser until the
temperature falls below the
boiling point when it
condenses back into a liquid
which is collected in a
container.
Chromatography

Chromatography  process used to
separate mixtures using a solvent
(water) that carries a solute (ink)
up a strip of paper


Heterogeneous mixtures can be
separated by physical means such
as filtration.
Homogeneous mixtures can be
separated by distillation,
crystallization, & chromatography.

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