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:

     

  3. Identify the elements on the reactant side.
  4. Count the number of atoms for each element.
  5. Identify the elements on the product side.
  6. Count the number of atoms on the product side.
  7. Are the 2 sides equal?  If not, the equation is not balanced.
  8. 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.
  9. Choose an element that is not balanced and begin to balance the equations.
  10. Continue until you have worked through all the elements.
  11. Once they are balance, count the final number of Reactants and Products.
  12. Write the balanced equation.
  13. 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.

Print activity cards on card stock instead of making index cards for quicker set up.

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.

 

Copyright 2000, E. S. Belasic