Balancing Chemical Equations Activity

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by Liz LaRosa

www.middleschoolscience.com

 

click here for a  pdf version of pages 1, & 3 and page 2

 

Updated Oct. 2007: Click here for activity cards ready to print in pdf format! Cards 1 & Cards 2

 

 

Objectives :

Materials:  These account for one complete set.  Color scheme is VERY important for visualization during the activity.

on 3x5 Index Cards

2 orange 6's

1 red "Reactants"

CO2

Fe

N2

Na2SO4

4 red 2's

2 black 7's

on 5x8 Index Cards

CH4

Fe3O4

NH3

O2

4 blue 3's

2 blue "+"

Al

C2H6

H2

Na

P4 

4 green 4's

1 black  "yield" sign  --->

Al2O3

CaCl2

 H2O

NaCl

P4O10

2 purple 5's

1 purple "Products"

C

CaSO4

H2O2 

Na2O

 

Pre Lab Questions:

Answer the following before you begin the activity:  

5H2

  1. What number represents the Coefficient? _____
  2. What number represents the Subscript? _____
  3. What element is represented by the letter "H"? _____
  4. How many "H's" do you have? _____

Procedure :

  1. Using your set of index cards, replicate the chemical equation onto your desk.
  2. Label the reactant side and the product side.

Record the following information into Table 1:

 

  1. Identify the elements on the reactant side.
  2. Count the number of atoms for each element.
  3. Identify the elements on the product side.
  4. Count the number of atoms on the product side.
  5. Are the 2 sides equal?  If not, the equation is not balanced.
  6. The  index cards numbered 2 - 7 are your coefficients.  They can ONLY be placed in front of the elements.  You can not change the subscripts.
  7. Choose an element that is not balanced and begin to balance the equations.
  8. Continue until you have worked through all the elements.
  9. Once they are balance, count the final number of Reactants and Products.
  10. Write the balanced equation.
  11. Can your equation be simplified?

Data :

Table 1 :   Chemical Equations (whole page, large boxes, sideways into lab book)

Make the following Equations on your desk

Reactants 

Products

Reactants - Final

Products - Final

Balanced Equation

H2 + O2 --> H2O

 

 

 

 

 

H2O2 --> H20 + O2

 

 

 

 

 

Na + O2 --> Na2O

 

 

 

 

 

N2 + H2 --> NH3

 

 

 

 

 

P4 + O2 --> P4O10

 

 

 

 

 

Fe + H2O --> Fe3O4 + H2

 

 

 

 

 

C + H2 --> CH4

 

 

 

 

 

Na2SO4 + CaCl2 --> 

CaSO4 + NaCl

 

 

 

 

 

C2H6 + O2 --> CO2 + H2O

 

 

 

 

 

Al2O3 --> Al + O2

 

 

 

 

  

Analysis/Results:

  1. What does "-->" mean?
  2. What side of the equation are the reactants found? products?
  3. Why must all chemical equations be balanced?
  4. Why can't the subscripts be changed?
  5. What does it mean to "simplify" the equation?

Conclusion

2-3 sentences on what you learned.

TEACHER NOTES:

Answers: http://www.middleschoolscience.com/chemanswers.htm

The index cards are a bit time consuming to create.  I had some students help at lunch time for a few days.  Once done, you can laminate them and have them forever!  The materials account for one complete set which is good for 2-3 students to use.

The color coding is very important for visualization.  It is easier and quicker to locate the elements that you are trying to balance.  If everything is  in black ink, its harder to distinguish the equation contents.

I use this towards the end of my chemistry unit, its a great assessment tool because it involves a vast amount of abilities that were learned during the chemistry unit.  I do the 1st two problems with the students to guide then through the procedure, and make sure they understand what is expected.  This activity takes about 2 - 3  "45 minute" class periods. I follow up with a worksheet as a homework assignment.

 

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