What is an element?
• Element- is a pure substance that cannot be
separated into a simpler substance by physical
or chemical means.
• Elements only have one type of particle.
– A pure substance is a substance in which there is
only one type of particle. Ex- atom
* In a 5g nugget of the element gold, every particle
is just like the rest of the particles in that 5g
• The particles of a pure substance are alike no
matter where that substance is found.
• Ex- the atoms of iron (element) are all alike
whether they are in a meteorite or in an iron
• Every element has a unique set of properties
– In order to identify an element, you can look at its
properties. These properties do not depend on
the size of the example.
Properties of an element
• There are several ways to identify an element.
You must look at their individual properties.
*elements are grouped according to their
shared properties. Ex. Iron, nickel and cobalt.
All three of these elements are shiny, all three
conduct thermal energy and electric current.
Since these three things have this stuff in
common, they are grouped together in a
grouped called Metals.
Three categories of elements
• Metals- these elements are shiny, are good
conductors of thermal energy and electric
current. They are malleable and ductile. Ex-
Lead, copper and tin
• Nonmetals-are elements that are dull and
that are poor conductors of thermal energy
and electric current. Solid nonmetals tend to
be brittle and unmalleable. Ex- the neon used
in lights and graphite used in pencils.
Categories of elements con’t
• Metalloids- also referred to as
semiconductors. These are elements that have
properties of both metals and nonmetals.
Some metalloids are shiny while others are
dull. Some conduct thermal energy and
currents while others do not. Some are
malleable and some are not. Ex- silicon, Boron
• A compound is a pure substance composed of
two or more elements that are chemically
combined. In a compound, a particle is formed
when atoms of two or more elements join
together. In order for these elements to
combine, they must react, or undergo a
chemical change together. Ex- table salt..NaCl,
water…H2O, sugar…CHO, carbon dioxide…co2,
baking soda, NaHCO
• The compound is a new pure substance that
is different from the elements that reacted to
• Compounds are not random combinations of
elements. When a compound forms, the
elements join in a specific ratio according to
• Each compound has its own unique set of
properties. These properties allow you to
distinguish it from other compounds. Ex-
Melting point, boiling point, density, color,
• A compound has different properties from the
elements that formed it. Ex- Table Salt- made
from two dangerous elements. When mixed
together, they form a harmless compound.
• Sodium- is a soft silvery white metal that
reacts violently with water
• Chlorine-is a poisonous, greenish yellow gas.
• Put the two together= sodium chloride!!
Table Salt, a perfectly safe, edible compound
Compounds can be broken down
• Some compounds can be broken down into
elements through chemical changes.
• Other compounds undergo chemical changes to
form simpler compounds.
• Ex- when mercury II oxide (compound) is heated,
it breaks down into the elements mercury and
• Also, if an electric current is passed through
melted table salt, the elements sodium and
chloride are produced.
Compounds CANNOT be……
• Broken down by physical changes. If you pour
water through a filter, there will be no change.
Compounds can only be broken down through
a chemical change.
• Compounds in Nature- Proteins, nitrogen
compounds, carbon dioxide.
• Compounds in Industry- Ammonia, aluminum.
• A mixture is a combination of two or more
substances that are not chemically combined.
• Substances in a mixture retain their identity-
because there is no chemical changes that
occurs in mixtures, each of the substances
keeps its original identity. Ex- cheese and
tomato sauce. They do not react to each
other, yet they mix. Thus, resulting in a
Mixtures can be physically separated
• If you don’t want pepperoni on your pizza, you
can easily pick them off, right? This is a physical
change of the mixture. The pizza and the
pepperoni keep their original identity whether or
not the pepperoni is on it or not.
• HOWEVER, not all mixtures are as easily
separated as pizza and pepperoni. Ex-saltwater.
You can’t easily pick the salt out of the water.
How would you remove salt from water?
Ways to separate mixtures
• Distillation- the process that separates a
mixture based on boiling points of the
compounds. Ex-distilling saltwater
• Magnet- can be used to separate a mixture of
the elements iron and aluminum. Iron is
attracted to the magnet, but the aluminum is
• A solution is a mixture that appears to be a single
substance, but is composed of particles of two or
• The process in which particles of substances
separate and spread evenly is known as
dissolving. Ex- Kool Aid and water.
• Solute- the substance that is dissolved-Kool Aid
• Solvent- the substance in which the solute is