2. What is a pure substance?
Pure substances are composed of one type of particle
Pure substances have fixed physical and chemical properties
Pure substances are either elements OR compounds
Gold is a pure substance. The
surrounding rock is a mixture of
different elements and
compounds.
3. MATTER
NO
Can it be physically
separated?
mixtures pure substances
Can it be chemically
decomposed?
YES NO
element
Concept Map
compound
4. Review: What are chemical elements?
Elements are pure substances composed of only ONE
type of atom.
Aluminum
Bromine
Sodium
5. There are approximately 117 known elements of which
only 88 occur naturally. Each element has its own
symbol. Elements are organized on the periodic table.
Gold (Au)
A Kaboom Key Concept!
An element is a pure substance composed entirely of one type
of atom!
6. A closer look at elements
Elements are substances composed of
one type of atom. For example, helium
gas (He), is composed of individual
helium atoms.
Some elements, like hydrogen gas (H2),
are composed of diatomic molecules.
Each molecule consists of two hydrogen
atoms that are chemically bonded
together. What are the other elements
that exist as diatomic molecules?
7. ELEMENTS THAT EXIST AS DIATOMIC MOLECULES
Remember:
BrINClHOF
or the super 7 Individually, these
elements only exist
as PAIRS of atoms.
When these
elements combine
in reactions to
make compounds,
they are no longer
elements so they
do not need to be
in pairs!
8. What is a compound?
are pure substances
composed of TWO or more elements
atoms held together by chemical bonds
can only be broken apart or formed by a chemical reaction
Sodium chloride Water Glucose
9. What happens in a chemical reaction?
reactants are converted to products
bonds are first broken
atoms are rearranged
new bonds form to make different compounds
10. This unit is all about the types of bonds that hold
atoms together to form compounds
ionic bonds in
compounds like
sodium chloride
covalent bonds in
compounds like
glucose
