Student Exploration: Balancing Chemical Equations · PDF fileStudent Exploration: Balancing Chemical Equations Vocabulary: coefficient, combination, compound, decomposition, double

Name: ______________________________________ Date: ________________________

Student Exploration: Balancing Chemical Equations

Vocabulary: coefficient, combination, compound, decomposition, double replacement, element,molecule, product, reactant, single replacement, subscript

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? ___________________________________________

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? _____________

Gizmo Warm-upIn a chemical reaction, reactants interact to form products.This process is summarized by a chemical equation. In theBalancing Chemical Equations Gizmo™, look at the floatingmolecules below the initial reaction: H2 + O2 H2O.

1. How many atoms are in a hydrogen molecule (H2)? ___

2. How many atoms are in an oxygen molecule (O2)? ____

3. How many hydrogen and oxygen atoms are in a water molecule (H2O)? ________________

4. In general, what does a subscript (such as the “2” in H2) tell you about the molecule?

_________________________________________________________________________

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? ________________

Activity A:

Balancingequations

Get the Gizmo ready:

Check that the Combination reaction is selectedand that all coefficients are set to one. (Thecoefficients are the numbers in the boxes.)

Introduction: The equation H2 + O2 H2O is unbalanced because there are two oxygen atomson the reactants side of the equation, and only one on the products side of the equation. Tobalance the equation, you cannot change the structure of any of the molecules, but you canchange 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 equalnumbers 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, andwater molecules until the equation is balanced. When you are done, turn on Showsummary to check your answer.

Write the balanced equation here: _____ H2 + _____ O2 _____ H2O

2. Solve: Turn off Show summary. Use the Choose reaction drop down menu to see otherequations, and balance them. Check your answers and then write the balanced equations.

_____ Al + _____ HCl _____ AlCl3 + _____ H2

_____ NaCl _____ Na + _____ Cl2

_____ Na2S + _____ HCl _____ NaCl + _____ H2S

3. Practice: Balance the following chemical equations. (These equations are not in the Gizmo.)

A. _____ Na + _____ Cl2 _____ NaCl

B. _____ Na + _____ H2O _____ NaOH + _____ H2

C. _____ Mg + _____ O2 _____ MgO

D. _____ KClO3 _____ KCl + _____ O2

E. _____ Al + _____ CuO _____ Al2O3 + _____ Cu

F. _____ CaCO3 _____ CaO + _____ CO2

G. _____ I2 + _____ Na2S2O3 _____ NaI + _____ Na2S4O6

H. _____ Mg + _____ P4 _____ Mg3P2

Activity B:

Classifyingreactions

Get the Gizmo ready:

Turn off Show summary and Show histograms.

Introduction: Chemical equations show how compounds and elements react with oneanother. An element is a substance consisting of one kind of atom, such as aluminum (Al) oroxygen gas (O2). A compound is a substance made of more than one kind of atom, such aswater (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 chemicalequations in the Gizmo as a guide, match the following definitions to the type of reaction.

____ One reactant is broken down into two ormore products.

____ Two or more reactants combine to formone product.

____ Two compounds react to form twodifferent compounds.

____ A compound reacts with an element toform a new compound and a differentelement.

A. Combination

B. Decomposition

C. Single replacement

D. Double replacement

2. Practice: Balance each of the chemical equations below. (Some equations may already bein 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 _______________________

B. ___ H2O + ___ SO3 ___ H2SO4 _______________________

C. ___ KI + ___ Cl2 ___ KCl + ___ I2 _______________________

D. ___ NaHCO3 ___ Na2CO3 + ___ H2O + ___ CO2 _______________________

E. ___ Zn + ___ HCl ___ ZnCl2 + ___ H2 _______________________

F. ___ BaCl2 + ___ Na2SO4 ___ BaSO4 + ___ NaCl _______________________

G. ___ Ag2O ___ Ag + ___ O2 _______________________

H. ___ Al + ___ CuCl2 ___ AlCl3 + ___ Cu _______________________

Balancing chemical equation 1:Visual representation of the unbalanced chemical equation: The scale

below is based on the number of elements not their mass.

____NH3 + ___O2 ___ NO + ____H2O

Graphic representation:

4

3

2

1

NR NP HR HP OR OP

You can use a bar graph to represent the count of each element on the

left side (Reactants side, NR) and the count on the right side ( Product

side, NP)

BeforeN H O

1 3 2

N

1

H

2

O

2

To be completed after balancing the equation:

____NH3 + ___O2 ___ NO + ____H2O

Graphic Representation:

NR NP HR HP OR OP

After N H ON H O

Balancing chemical equation 2:

_____C6H5COOH + _____ O2 ____CO2 + _____ H2O

BeforeC H O

C H O

_____C6H5COOH + _____ O2 ____CO2 + _____ H2O

AfterC H O C H O

Balancing chemical equation 3:_____KMnO4 + ____HCl ____KCl + ____MnCl2 + ____Cl2 + ____ H2O

BeforeK H O Mn Cl

K H O Mn Cl

_____KMnO4 + ____HCl ____KCl + ____MnCl2 + ____Cl2 + ____ H2O

AfterK H O Mn Cl K H O Mn Cl

Balancing chemical equations: using guess and check

Chemical Equation 1:

____NH3 + ___O2 ___ NO + ____H2O

Reactants Products

N: 1 N: 1

H: 3 H: 2

O: 2 O: 1 + 1

____NH3 + ___O2 ___ NO + ____H2O

Before

After

N H O

1 3 2

N

1

H

2

O

2

N H ON H O


_____C6H5COOH + _____ O2 ____CO2 + _____ H2O

_____C6H5COOH + _____ O2 ____CO2 + _____ H2O

Before

After

C

7

H

6

O

2

C

1

H

2

O

3

C H O C H O

Chemical Equation 3:_____KMnO4 + ____HCl ____KCl + ____MnCl2 + ____Cl2 + ____ H2O

_____KMnO4 + ____HCl ____KCl + ____MnCl2 + ____Cl2 + ____ H2O

Before

After

K H O Mn Cl

K H O Mn Cl

Balancing chemical equations –Using systems of Eq.


___a_NH3 + _b_O2 _c_ NO + __d__H2O

Systems of equations:

N:

H:

O

Simplified form and solve:

a = ________ b = ______ c = ________ d = _________


__a__C6H5COOH + __b__ O2 __c__CO2 + __d__ H2O


C:

O:

H:

Simplified form and solve:

a = ______ b = _______ c = ________ d = _________


__a_KMnO4 + __b_HCl __c_KCl + __d_MnCl2 + __e_Cl2 + __f_ H2O

Systems of equations

K:

Mn:

O:

H:

Cl:

Simplified:

Balancing chemical equations—Using Matrices


___a_NH3 + _b_O2 _c_ NO + __d__H2O


N:

H:

O

Matrix representation and solve:

a = ________ b = ______ c = ________ d = _________




C:

O:

H:


a = ______ b = _______ c = ________ d = _________




K:

Mn:

O:

H:

Cl:


Graphing calculatorFollow these keystrokes on the TI-83 or TI-84:1) Press 2nd, x-1. This opens the matrix menu.2) Move curser to “EDIT”. This opens to Matrices; PRESS “1” for matrix

[A].3) Enter the matrix dimensions: # of Rows X # of Columns4) Enter the elements of the matrix going across the rows and pressing

“ENTER” after each number.5) Press “2nd” “Quit” to go back to home screen.6) Press “2nd”, “Matrix”,” →” to “MATH”. 7) Press down arrow and scroll to “B” which is “rref[“ (reduce row

echelon form)8) Press “2nd”, “Matrix” then “1” ) That will paste matrix [A] into home

screen.9) To make sure your answer is in Fraction Form: Press “Math”, Pres

“ENTER” or “1” for (Frac)10) Press “ENTER” for the final answer.

The answers are in terms of the last variable and equated to zero.Each variable is in terms of last variable.

Example of final answer: ( From a 3X4 matrix)

a – (2/3)d = 0b - (5/6)d = 0c – (2/3)d = 0

By setting “d” to be the lowest common denominator, you will be able tofind the least set of whole numbers that will balance the equation.

Therefore, let d =6, then a = 4, b = 5, and c = 4

CHEMICAL Equations for DC Mtg:

Chemical Equation 1: (easy) KEY

___a_NH3 + _b_O2 _c_ NO + __d__H2O

a = 4 , b = 5, c 4 , and d = 6


N: 1a + 0b = 1c + 0d

H: 3a + 0b = 0c + 2d

O: 0a + 2b = 1c + 1d

Simplified form:

a = c

3a = 2d

2b = 1c

Chemical Equation 2: Medium


A = 2, b = 15, c = 14, d = 6


C: 7a + 0b = 1c + 0d

O: 2a + 2b = 2c + 1d

H: 6a + 0b = 0c + 2d

Simplified form:

Chemical Equation 3: Above medium KEY


A = 2, b = 16, c = 2, d = 2, e = 5, f = 8


K:

Mn:

O:

H:

Cl:

Simplified:

Visual Representation of Roots and Affixes: Metric System

1. Read and study the information in each row.2. Fill in any boxes that are empty, that is, they do not have information. For example, for theword kilogram, the blank item is the Synonym, Example or Sentence box.3. If you use what you learn in the Affix and Root Meaning boxes, you can fill in missinginformation for the other Affix and Root Meaning boxes.

Root Wordwith Affix

Affix andRoot

Meaning

Synonym, Example orSentence

Definition VisualRepresentation

(Picture)kilogram Kilo-: one

thousand

-grama: ametric unit ofmass equal toone thousandthof a kilogram

the base unit of mass inthe Metric System, aninternational system ofmeasures used by mostcountries

A kilo gold bar

kilometer Kilo-: one onethousandths

-meter: Thestandard unit oflength in themetric system isthe meter

Other units of lengthand their equivalentsin meters:1 millimeter = 0.001meter1 centimeter = 0.01meter1 decimeter = 0.1meter1 kilometer = 1000meters

The standard unit oflength in the metricsystem is the meter.We symbolize theselengths as follows:1 millimeter = 1 mm1 centimeter = 1 cm1 meter = 1 m1 decimeter = 1 dm1 kilometer = 1 km

centipede centi- onehundred

-pedis: foot

A centipede is anarthropod, an invertebrateanimal with a segmentedbody; each segment hasone pair of legs.

centimeter How wide is the ring incentimeters?

Visual Representation of Roots and Affixes #6: Metric System

Root Wordwith Affix

Affix andRoot

Meaning

Synonym, Exampleor

Sentence

Definition Visual Representation(Picture)

milipede mili-oneone-thousandthsof the SIbase unit,the kilogram-pedis:

An arthropod is aninvertebrate animal with asegmented body; eachsegment has two pairs oflegs.

Decimeter

Millimeter

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Student Exploration: Balancing Chemical Equations · PDF fileStudent Exploration: Balancing Chemical Equations Vocabulary: coefficient, combination, compound, decomposition, double