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Name: ___Robert Aubert___________________________________
1/29/2013_______________________
Date:
Student Exploration: Balancing Chemical Equations
DEFINE Vocabulary: coefficient
Combination- a chemical reaction when two reactions combine to make one
Compound- a substance consisting of two or more elements
Decomposition- the separation of a substance into a simpler form
Double replacement- multiple elements that are getting swapped
Element- a substance that cannot be broken down into simpler substances by any chemical
mean
Molecule- a group of two or more atoms linked together by sharing electrons
Product- what you get from a chemical reaction, the final form
Reactant- a substance participating in a chemical reaction
Single replacement- one of the elements swapping with another
Subscript- a figure, letter, or symbol written below or to the side of another
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
The scouts are making s’mores out of toasted marshmallows, chocolate, and graham crackers.
1 What is wrong with the image below? ___not enough graham
crackers________________________________________
2. Assuming a s’more requires two graham crackers, one marshmallow, and one piece of
chocolate, how many s’mores could you make with the ingredients shown? ___2__________
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Gizmo Warm-up
In a chemical reaction, reactants interact to form products.
This process is summarized by a chemical equation. In the
Balancing Chemical Equations Gizmo™, look at the floating
molecules below the initial reaction: H2 + O2  H2O.
1 How many atoms are in a hydrogen molecule (H2)?
_2__
2 How many atoms are in an oxygen molecule (O2)?
__2__
3 How many hydrogen and oxygen atoms are in a water molecule (H2O)?
_______3_________
4 In general, what does a subscript (such as the “2” in H2) tell you about the molecule?
________how many Hydrogen molecules there is
______________________________________________________________
5 A chemical equation is balanced if the number of each type of atom on the left side is
equal to the number of each type on the right side. Is this reaction balanced?
_______no_________
Activity A:
Balancing
equations
Get the Gizmo ready:
● Check that the Combination reaction is selected
and that all coefficients are set to one. (The
coefficients are the numbers in the boxes.)
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Introduction: The equation H2 + O2  H2O is unbalanced because there are two oxygen
atoms on the reactants side of the equation, and only one on the products side of the equation.
To balance the equation, you cannot change the structure of any of the molecules, but you can
change the number of molecules that are used.
Question: How are chemical equations balanced?
1 Balance: Turn on Show histograms. The equation is balanced when there are equal
numbers of each type of atom represented on each side of the equation.
In the Gizmo, use the up and down arrows to adjust the numbers of hydrogen, oxygen, and
water molecules until the equation is balanced. When you are done, turn on Show
summary to check your answer.
Write the balanced equation here: __2___ H2 + ___1__ O2  __2___ H2O
2 Solve: Turn off Show summary. Use the Choose reaction drop down menu to see
other equations, and balance them. Check your answers and then write the balanced
equations.
__2___ Al + ___6__ HCl  __2___ AlCl3 + _3____ H2
___2__ NaCl  __2___ Na + _____ Cl2
_____ Na2S + ___2__ HCl  ____2_ NaCl + _____ H2S
3 Practice: Balance the following chemical equations. (These equations are not in the
Gizmo.)
A ___2__ Na + ___1__ Cl2  __2___ NaCl
B _2____ Na + __2___ H2O  __4___ NaOH + __1___ H2
C ___2__ Mg + __1___ O2  ___2__ MgO
D ___2__ KClO3  ___2__ KCl + __3___ O2
E ___4__ Al + ___6__ CuO  ____2_ Al2O3 + ___6__ Cu
F
___1__ CaCO3  ___1_ CaO + ____1_ CO2
G ___1__ I2 + ___4__ Na2S2O3  ___2__ NaI + __2___ Na2S4O6
H _6____ Mg + ___1__ P4  __2___ Mg3P2
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Activity B:
Get the Gizmo ready:
● Turn off Show summary and Show histograms.
Classifying
reactions
Introduction: Chemical equations show how compounds and elements react with one
another. An element is a substance consisting of one kind of atom, such as aluminum (Al) or
oxygen gas (O2). A compound is a substance made of more than one kind of atom, such as
water (H2O) or table salt (NaCl).
Question: How are chemical reactions classified?
1 Match: Most chemical reactions can be classified as one of four types. Using the
chemical equations in the Gizmo as a guide, match the following definitions to the type of
reaction.
b____ one reactant is broken down into two or more products.
_a___ Two or more reactants combine to form one product.
__d__ two compounds react to form two different compounds.
__c__ A compound reacts with an element to form a new compound and a different
element.
A Combination
B Decomposition
C Single replacement
D Double replacement
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2 Practice: Balance each of the chemical equations below. (Some equations may already
be in balance.) In the space to the right, classify the reaction as a combination,
decomposition, single replacement, or double replacement reaction.
A ___ AgNO3 + ___ KCl  ___ AgCl + ___ KNO3
double replacement________________
B ___ H2O + ___ SO3 ___ H2SO4
synthesis_______________________
C __2_ KI + ___ Cl2  _2__ KCl + ___ I2
Synthesis_______________________
D ___ NaHCO3  ___ Na2CO3 + ___ H2O + ___ CO2
__________combustion____________
E ___ Zn + __2_ HCl  ___ ZnCl2 + ___ H2 ___single
replacement____________________
F
___ BaCl2 + ___ Na2SO4  ___ BaSO4 + _2__ NaCl
Replacement______________________
G __2_ Ag2O  _4__ Ag + ___ O2
_______decompostion________________
H 2___ Al + __3_ CuCl2  __2_ AlCl3 + __3_ Cu
single replacement______________
Double