SIGNS OF CHEMICAL
CHANGES
Chemical Property
-The ability of a substance to
undergo a change that alters
its identity.
-A characteristic that cannot
be observed without altering
the substance
Chemical Change
• Change in which the
composition of a substance
changes
– Changes are not easily
reversed
Signs of Chemical
Changes
1. Change in Color
2. Change in
Temperature
3. Change in Odor
4.BubblesGas produced
5. Precipitate (solid)
is formed
+
Atom
• The smallest particle of any
pure element.
• Only 1 atom
• Example: 1 atom of H
Element
• A substance made up of the
SAME type of atom
• Example: O2
Compound
-a substance made up of atoms
of two or more DIFFERENT
elements combined in a
specific ratio
Ex. NaCl or H2O
Molecule
-Group of 2 or more atoms held
together by chemical bonds.
Atoms may or may not be of
the same element
EX. NaCl
or O2
Chemical Formula
-a way of describing the
number of atoms that make
up one molecule of a
compound
Ex. C6H1206
H20
Subscript
-the number of atoms of
that particular element
• SUB-Below
EX. H20
or CH4
Coefficient
-determines the number of
molecules (groups) of the
formula
-This number will be DISTRIBUTED
just like in math. It applies to
each element and is multiplied
by each subscript to find the
total number of atoms of each
element and a total number of
atoms in the molecule.
EX. 2H2O
4Al2(SO4)3
CH4
H
H
C
H
H
2H20
H
H
O
H
H
O
C=Yellow O=White H=Orange N=Pink
• Atom
• Element
• Compound
• Molecule
• C, O, H, N
• C,C2, O, O2, H, H2,
N,N2
• CH4, H2O, CO2
• CH4, H2O, H2, O2, CO2
• 2H2O, 3O2, 2CO2
Identify the Elements, give the
number of atoms of each
element, and the total number of
atoms in the formula
1) 2FeCl3
2) KMnO4
3) 3HgO
4)C6H5COOH
5) 2HCl
6. 4Fe2O3
7. NaClO
8. ZnCl2
9. KClO3
10.24F2
11.3Al2(SO2)3
Chemical Reaction
-a change in which one or more
chemical substances are
rearranged to form different
substances.
Chemical Equation
-a way to show a chemical
reaction using chemical
formulas.
-made up of reactants and
products
Reactants
Products
Yield
the amount of product
obtained as a result of a
chemical reaction

Components of chemical
reaction
Reactants
Products
-are indicated on
-are indicated on
the right side
the left side
-new substances
-substances that
created/PRODUCED
react in a
in a chemical
chemical
reaction
reaction
-inputs
-Outputs
-Ingredients
-Cake
Example
Reactants
Products
CH4 + 2O2  CO2 + 2H2O
# of atoms of that element
Coefficient (# of molecules)
Law of Conservation of
Mass
-what goes into a chemical
reaction will come out of a
chemical reaction.
-atoms found on the reactants
side will also be found on the
products side. They will be
broken apart and rearranged
to create new substances.
-creates a “Balanced” equation
CH4 + 2O2  CO2 + 2H2O
6CO2 + 6H2O  C6H12O6 + O2
Modeling Balanced/Unbalanced
Equations
• 4P + 5O2  P4O10
• Mg + O2  MgO
• 2Al2O3  4Al + 3O2
• 2HgO  2Hg + O2
• BaCl2 + H2SO4  BaSO4 + HCl
Identify Balanced
Equations
1) 2Fe + 3Cl2  2FeCl3
2) KMnO4 + HCl  KCl + MnCl2 + H2O + Cl2
3) HgO  Hg + O2
4) C6H5COOH + O2  CO2 + H2O
5) H2 + Cl2  2 HCl
6) 2Fe + 3O2  Fe2O3
7) 2NaOH + Cl2  NaCl + NaClO + H2O
8) Zn + 2HCl  ZnCl2 + H2
9) KClO3  KCl + O2
10)S8 + 24F2 8SF6
Balancing Equations
1)Determine number of atoms for
each element.
2) Pick an element that is not equal
on both sides of the equation.
3)Add a coefficient in front of the
formula with that element and
adjust your counts.
4) Continue adding coefficients to
get the same number of atoms of
each element on each side.
Balancing Equations
N2 +
H2 
NH3
Balancing Equations
NaCl +
F2 
NaF + Cl2
Balancing Equations
Practice
1.P + O2  P2O5
2.KClO3  KCl + O2
3.H2 + O2  H20
4.H20 + O2  H2O2
5. K + MgBr  KBr + Mg