• Make two columns on a sheet of paper. Title 1
column Physical Changes and the 2nd column
title Chemical Changes.
• From the next slide, categorize each item
either physical or chemical change.
PHYSICAL OR CHEMICAL Change?
Candle wax
melting
Wood burning
Cake baking
Ice freezing
Iron rusting
Salt dissolved in
water
Fireworks
exploding
Leaves
Cooking an egg
changing colors
Breaking an egg
Cutting paper
Water boiling
Mixing baking
soda and water
Tarnished silver
Battery
corrosion
Chemistry Background
• In order for elements to be completely stable
(or un-reactive) they need to have 8 electrons
in their outside energy level.
• An element with 8 electrons on its last level is
a happy element. The “happiest” elements on
the table are the noble gases.
• Exception: Helium is happy with two electrons
in its outer energy level.
Selection Process
• Sodium contains 1 valence electron on its
outside shell. It is very unhappy and unstable.
It needs a “partner” to balance it out. But,
only one type of “partner” will do. It must
have 7 valence electrons!
Match
• Chlorine looks like a good partner because it
has 7 valence electrons!
• Draw a Lewis Dot Diagram for Sodium and
Chlorine.
Chemistry of Sodium and Chlorine
• If sodium gives away its last electron, it will be left with 8
on its last shell! Therefore it will be happy!
8
1e-
2
11P+
positive
The sodium atom then becomes a ____________ion.
Chemistry of Sodium and Chlorine
• If chlorine accepts the electron from sodium it
will now have 8 electrons on its outside shell
therefore it will be happy!
8
7e-
1e-
2
17P+
negative
The chlorine atom then becomes a ___________ ion.
Ion

an atom that has an electrical
charge because it no longer has
an equal number of protons and
electrons.
6P+
6N
2e- 3e-
Rule of Eight
7e-
1e- 11P+
8e1e1e-
17P+
Sodium Chloride
8e-
Molecule
Copy the table and
identify if each of
the following
compounds is possible.
Explain why!
LiF
HHe
BeO
NaCl
KI
CaS
MgO
FAr
KCl
Possible
Not Possible
Models of Compounds
• Make the following compounds by fitting the
puzzle pieces together. Use the names of the
compounds as clues.
–
–
–
–
–
Sodium chloride
Calcium oxide
Carbon dioxide
Calcium chloride
Aluminum oxide
• Draw the compounds in your notebook and
write the name of the compound and its
chemical formula. Include the Lewis Dot
Diagram for each atom
Chemical Equations
• Shorthand way that scientists use to represent
what takes place in a chemical reaction.
• Chemical equations consist of many different
components (parts).
Components of a Chemical Equation
2Na2O2 + 2H2O -> 4NaOH + O2
Copy the chart and fill in the spaces.
Chemical Formula
NaCl
CO2
H3PO4
2H2SO4
H2O
2C6H12
Total # of Elements in
the Formula
Total # of Atoms in
the Formula
Symbol
Ex: H, Na
1 or 2 letters used to represent an
element
Place of discovery, scientist, or other
language such as Latin or Greek.
First letter capitalized, second letter lower
case.
Chemical Formula
Ex: NaCl, H2O
A combination of symbols and numbers
that represent the number and types of
elements(atoms) present in a compound.
Subscript
Ex: CO2, H2O2
Small number written to the right and below
the normal line of letters.
Shows how many atoms of each element are
present in a substance.
No subscript means there is only one atom
present.
Chemical Reaction
• Ex: H2 (g) + O (g)
H2O (liquid)
• When substances interact to form one or more new
substances with different properties than the
original substance
Chemical Equation
• Ex: 2H2 + 2O2
2H2O2
• A combination of chemical formulas used to
describe what happens in a chemical reaction.
• The equation identifies the reactants and
resulting products.
Coefficient
• 2Na + 2Cl
2NaCl
• A number written in front of a chemical
formula to show how many molecules of
that substance are present.
Reactants
• 2CO2
2C + 2O2
• Formulas written on left side of arrow (
)
• Starting substance or substances in a chemical
reaction
Product
• 2Fe + O2
2FeO
• Formulas written on the right side of arrow (
)
• New substance or substances formed in a chemical
reaction
Yields
• H2 + O2
H2O2
• Arrow shows a reaction has taken place.
• The reactants have reacted to produce a
new substance (the product)
Compound
H2O, CO2, CO
A substance composed of two or more
elements chemically combined
in a definite proportion
Physical Change
• A change in which the characteristics
of a substance are only changed
physically and the original properties
stay the same.
• Physical properties of matter are characteristics
that you can observe about the matter.
• EX: color, shape, size, density, melting point, boiling
point, freezing point, specific heat, state, metal,
nonmetal, metalloid, evaporation, condensation,
crystallization, conductivity, magnetism, luster,
malleability, taste, dissolving, odor, texture, volume,
mass, length, temperature
Physical Properties
Chemical Changes
• A change in which a substance or
substances is changed into one
or more new substances with
different properties than the
original substances
Chemical Properties
• Chemical properties of matter are the
properties that indicate whether an object can
undergo a chemical reaction.
• EX. flammable, reactive, corrosive, tarnishing,
rusting oxidation …
Law of Conservation of Mass
• Matter is neither created or destroyed, only
changed.
• The number of atoms in the reactants must
be equal to the number of atoms in the
product.
Precipitate
• A solid that forms as a result of a chemical
reaction
• It will pull out and fall to the bottom of the
container
Law of Conservation of Mass
• Reactants
• NaHCO3 + HC2H3O2
yields
Products
CO2 + H2O + NaC2H3O2
• 1 sodium, 5 hydrogens, 3 carbons, 5 oxygens
• BALANCED!!!
• Number and kind of atoms on the reactant side
must equal the number and kinds of atoms on the
CHEMICAL CHANGES Occur
When:
Different substances with new
properties are formed.
Chemical Equations
• You can explain a chemical reaction on paper by
using a chemical equation.
yields
• reactants
• What you START with
with
products
What you end up
Chemical Reactions
Involve the breaking or forming of
chemical bonds causing atoms to
become rearranged into a new
substance or substances.
What to look for in a chemical
change:
• New substance with new properties
• Energy involved
(heat being released, heat being
absorbed)
• Gases released
• Color change
• A precipitate( a solid that separates out of a
reaction)