Once you’re in, you’re in. Go to the bathroom/get water before you
enter.
zero
When the bell rings, voice at
, working on the Do Now in Do Now
Form (flip over the one you have from last week).
Pick up daily handouts. Pick up turned back docs.
Turn in your MARSHMALLOW ACTIVITY
(A LOT ARE MISSING!)
TURN IN ANY TEST CORRECTIONS
TURN IN ANY TAKE HOME TESTS
TURN IN ANY MAKE UP WORK
HAVE YOUR HOMEWORK ON YOUR DESK DO NOT
TURN IN
Do Now 10/15/2013
Find the percent composition of all of the elements in NaOH (Find
Na, O, and H)
Draw the Lewis structure to determine the molecular geometry,
bond angles, and main intermolecular force in NaOH
Do Now Review 10/15/2013
 Find the percent composition of all of the elements
in NaOH (Find Na, O, and H)
 Draw the Lewis structure to determine the molecular
geometry, bond angles, and main intermolecular
force in NaOH
Tutoring and Makeup Work
 Tuesday/Thursday 2:30-3:30
 Wednesday at Lunch (let me know ahead of time this
week)
 TWO weeks left in the quarter – if your name is on the
board , you owe me a quiz or a test!!
 Zeros
Homework
 Textiles handout
 Any makeup work / late work
 Balancing reactions handout**
**graded
Objectives
SWBAT
 Determine if a chemical reaction has occurred based
on precipitate formation, product testing, color change,
and temperature change.
 Write and balance chemical equations
 Use reference tables to predict products for all types of
reactions to show the conservation of mass.
Double Replacement
Reactions
The ions of two compounds exchange places
in an aqueous solution to form two new
compounds.
AX + BY  AY + BX
One of the compounds formed is usually a
precipitate, an insoluble gas that bubbles out of
solution, or a molecular compound, usually
water.
Combustion Reactions
A substance combines with oxygen, releasing a
large amount of energy in the form of light and
heat.
Reactive elements combine with oxygen
P4(s) + 5O2(g)  P4O10(s)
(This is also a synthesis reaction)
The burning of natural gas, wood, gasoline
C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)
Acid-Base Reactions
 This is a special kind of double displacement reaction
that takes place when an acid and base react with each
other. The H+ ion in the acid reacts with the OH- ion in the
base, causing the formation of water.
 Generally, the product of this reaction is some ionic salt
and water:
HA + BOH ---> H2O + BA
 One example of an acid-base reaction is the reaction of
hydrobromic acid (HBr) with sodium hydroxide:
HBr + NaOH ---> NaBr + H2O
Exit Ticket
1. MgCl2 + Li2CO3  MgCO3 + 2 LiCl
Reaction Type _______________________
2. P4 + 3 O2  2 P2O3
Reaction Type _______________________
3. 2 NO2  2 O2 + N2
Reaction Type _______________________
CHEMICAL REACTIONS
Reactants: Zn + I2
Product: Zn I2
Chemical Equations
Their Job: Depict the kind of reactants
and products and their relative
amounts in a reaction.
4 Al (s) + 3 O2 (g) ---> 2 Al2O3 (s)
The numbers in the front are called
stoichiometric coefficients
The letters (s), (g), and (l) are the
physical states of compounds.
Introduction
 Chemical reactions occur when bonds
between the outermost parts of atoms are
formed or broken
 Chemical reactions involve changes in
matter, the making of new materials with
new properties, and energy changes.
 Symbols represent elements, formulas
describe compounds, chemical equations
describe a chemical reaction
Chemical Change definition
(two equally good definitions)
 A chemical reaction is the process by which
one or more substances change into one or
more new substances whose chemical and
physical properties differ from those of the
original substances.
 Chemical Reaction: the process by which one
or more substances change to produce one or
more different substances.
Keys to look for in Chemical
Reactions
1. Formation of Gas
2. Color Change
3. Temperature Change
4. Formation of Precipitate
1. A precipitate forms when a substance comes out of a
solution and forms a solid
Are these chemical reactions?
 A forest fire destroys acres of land. There is a lot of smoke and the trees
turn to charcoal. (yes))
 When making hot chocolate clear water turns brown when you mix cocoa
in (no)
 An old wheelbarrow is left out in the rain and rusts (yes)
 Water forming on the outside of a cold glass of water (no)
 Ice cream melting (no)
 A raw egg gets cooked (yes)
 When Alka Sletzer is dropped into water it fizzes (yes)
 Soda fizzes and bubbles rise as you pour it in a glass (no)
 When you crack a glow stick, hydrogen peroxide mixes with other
chemicals causing it to glow and warm up (yes)
Parts of a Reaction Equation
 Chemical equations show the conversion of reactants (the
molecules shown on the left of the arrow) into products (the
molecules shown on the right of the arrow).
 A + sign separates molecules on the same side
 The arrow is read as “yields”
 Example
C + O2  CO2
 This reads “carbon plus oxygen react to yield
carbon dioxide”
 The charcoal used in a grill is basically carbon. The
carbon reacts with oxygen to yield carbon dioxide. The
chemical equation for this reaction, C + O2  CO2,
contains the same information as the English
sentence but has quantitative meaning as well.
Chemical Equations
Because of the principle of the
conservation of matter,
an equation
must be
balanced.
It must have the same
number of atoms of the
same kind on both sides.
Lavoisier, 1788
Symbols Used in Equations
 Solid (s)
 Liquid (l)
 Gas (g)
 Aqueous solution (aq)
H2SO4
 Catalyst
 Escaping gas ()
 Change of temperature ()
Balancing Equations
 When balancing a chemical reaction you
may add coefficients in front of the
compounds to balance the reaction, but
you may
not
change the subscripts.
 Changing the subscripts changes the
compound. Subscripts are determined
by the valence electrons (charges for
ionic or sharing for covalent)
The SEVEN Diatomic
Molecules
 Hydrogen (H2)
 Nitrogen (N2)
 Oxygen (O2)
 Fluorine (F2)
 Chlorine (Cl2)
 Iodine (I2)
 Bromine (Br2)
Subscripts vs.
Coefficients
 The subscripts
tell you how
many atoms of
a particular
element are in a
compound. The
coefficient tells
you about the
quantity, or
number, of
molecules of
the compound.
Chemical Equations
4 Al(s) + 3 O2(g) ---> 2Al2O3(s)
This equation means
4 Al atoms + 3 O2 molecules
---produces--->
2 molecules of Al2O3
AND/OR
4 moles of Al + 3 moles of O2
---produces--->
2 moles of Al2O3
Steps to Balancing Equations
There are four basic steps to balancing a chemical equation.
1. Write the correct formula for the reactants and the products. DO
NOT TRY TO BALANCE IT YET! You must write the correct
formulas first. And most importantly, once you write them
correctly DO NOT CHANGE THE FORMULAS!
2. Find the number of atoms for each element on the left side.
Compare those against the number of the atoms of the same
element on the right side.
3. Determine where to place coefficients in front of formulas so that
the left side has the same number of atoms as the right side for
EACH element in order to balance the equation.
4. Check your answer to see if:
 The numbers of atoms on both sides of the
equation are now balanced.
 The coefficients are in the lowest possible whole
number ratios. (reduced)
Some Suggestions to Help You
Some Helpful Hints for balancing equations:
1. Take one element at a time, working left to
right except for H and O. Save H for next to
last, and O until last.
2. IF everything balances except for O, and
there is no way to balance O with a whole
number, double all the coefficients and try
again. (Because O is diatomic as an
element)
3. (Shortcut) Polyatomic ions that appear on
both sides of the equation should be
balanced as independent units
Balancing Equations
2 H2(g) + ___ O2(g) ---> ___
2 H2O(l)
___
What Happened to the Other
Oxygen Atom?????
This equation is not balanced!
Two hydrogen atoms from a hydrogen
molecule (H2) combines with one of the
oxygen atoms from an oxygen molecule
(O2) to form H2O. Then, the remaining
oxygen atom combines with two more
hydrogen atoms (from another H2 molecule)
to make a second H2O molecule.
Balancing
Equations
2 Al(s) + ___
3 Br2(l) ---> ___ Al2Br6(s)
___
Balancing
Equations
____C3H8(g) + _____ O2(g) ---->
_____CO2(g) + _____ H2O(g)
____B4H10(g) + _____ O2(g) ---->
___ B2O3(g) + _____ H2O(g)
Balancing Equations
Sodium phosphate + iron (III) oxide  sodium oxide
+ iron (III) phosphate
Na3PO4 +
Na2O +
Fe2O3 ---->
FePO4