Elements, Compounds & Mixtures
How everything is put together.
Classification of Matter
Elements
 Matter that has the same
composition and properties
throughout is called an
element.
• When different elements
combine, other substances
are formed.
Elements
 Contains only one
particle
 Can exist in 3 states
of matter solid,
liquid, and gas
Picture from
http://www.ilpi.com/msds/ref/gifs/statesofmatter.gif
Compounds
 Ban DHMO?
 DHMO is dihydrogen monoxide.
 Evaluate the following link and
decide if this potentially dangerous
chemical should be prohibited.
 www.dhmo.org
Compounds
 A compound is a substance
whose smallest unit is made
up of atoms of more than one
element bonded together.
• Compounds often have
properties that are different
from the elements that make
them up.
• Examples: Water, salt, sugar
Compounds
General Rules:
- Only write the name of the metallic element
first
- Write the number of atoms of any element in
the compound in subscript
(applies to only 2 or more atoms)
- “ide” will always be written at the end of the
non metal element
Compound
Properties
Compounds are formed by atoms of
different elements. However, they do not
have the properties as them.
Because of chemical bonds, compounds
cannot be broken down by physical means.
They can only be broken down by
chemical reaction or electricity.
How do we name compounds?
Rule 1
A compound made up of two elements
has a name that ends in -ide.
• Sodium chloride — made up of the elements
sodium and chlorine
• Zinc oxide — made up of the elements zinc
and oxygen
• Carbon dioxide — made up of the elements
carbon and oxygen
Fixed Composition of Compounds
A compound is made up of different elements
chemically combined in a fixed ratio.
For example, water (H2O) is a compound made
only by joining together two atoms of hydrogen
to one atom of oxygen.
That is, the ratio of hydrogen atoms to oxygen
atoms in water is always 2 : 1.
Chemical Formula of a Compound
A compound can be represented by a chemical
formula.
The chemical formula states
• the types of atoms (i.e. elements) in the
compound,
• the ratio of the different atoms in the
compound.
Types of atoms:
hydrogen, oxygen
Ratio of H to O = 2:1
How do we write chemical
formula?
Rule 1
For many compounds that contain both
metallic and non-metallic elements, the
symbol of the metallic element is written
first.
• calcium oxide (CaO)
• sodium chloride (NaCl)
• magnesium carbonate (MgCO3)
How do we write chemical formula?
Rule 2
The number of atoms is written as a
subscript, to the right of the atom’s symbol.
• water (H2O, not H2O or 2HO)
• magnesium carbonate
(MgCO3, not MgCO3 or MgC3O)
How do we write chemical formula?
Rule 3
It is not necessary to write the
subscript ‘1’.
• water (H2O, not H2O1)
• calcium oxide (CaO, not
Ca1O1)
How do we write chemical formula?
Rule 4
The oxygen atom is usually written at
the end of the formula.
• water (H2O, not OH2)
• carbon dioxide (CO2, not O2C)
• nitric acid (HNO3, not O3NH)
Let’s try it…
 How many atoms of each element are there in
the compound?
 Sulfuric Acid H2SO4
 __ Hydrogen
 __ Sulfur
 __ Oxygen
 Hydrogen Peroxide H2O2
 __ Hydrogen
 __ Oxygen
And some more formulas…
 Carbon Dioxide CO2
 __ Carbon
 __ Oxygen
 Carbon Monoxide CO
 __ Carbon
 __ Oxygen
 Calcium Carbonate CaCO3
 __ Calcium
 __ Carbon
 __ Oxygen
Compound Review
 A pure compound has the same elements
and the same amount of elements all of
the time
 Elements are chemically combined
 Compound properties are different from
the properties of the elements
 They cannot be separated physically
 Physical properties such as boiling point or
melting point of pure substances are do not
change
Mixtures
 A mixture is a
combination of two
or more substances
where there is no
chemical
combination or
reaction.
Mixtures combine
physically in no
specific
proportions.
They just mix.
Solids, liquids and
gases can be
combined to
create a mixture.
Mixture Types
 MIXTURES MAY BE
HOMOGENEOUS OR
HETEROGENEOUS
Homogeneous Mixtures
 Homogeneous Mixtures:
 The prefix: "homo"- indicates
the same
 Have the same uniform
appearance and composition
throughout
Solutions
 SOLUTIONSare homogeneous
mixtures
What is a solution?
 A solution is a
mixture of two or
more substances.
 At least two
substances must
be mixed in order
to have a solution
A solution has two parts
 The substance
in the smallest
amount and
the one that
DISSOLVES is
called the
SOLUTE
The substance in the
larger amount is called
the SOLVENT - it does
the dissolving
IN most common
instances water is the
solvent
Examples of solutions
 Salt water
 Clean Air
 Vinegar
Heterogeneous Mixtures:
 The prefix: "hetero"- indicates
difference
 A heterogeneous mixture consists
of visibly different substances or
phases
 Two or more parts can be seen
Examples:
 Pizza
 Sandwich
 Chex Mix
Suspensions
 A SUSPENSION is a
heterogeneous mixture of
large particles
 These particles are visible
and will settle out on
standing
 Examples of suspensions
are: fine sand or silt in water
or Italian salad dressing
Classification of Matter
Compounds vs Mixtures
Compounds
•Combine
chemically
forming
molecules
•Combine in set
proportions
•Separated
chemically
Mixtures
•Not chemically
combined
•Can combine
in any
proportion
•Separated
physically