Intro to Balancing Chemical Equations Simulation
Concept Review
1. What is the law of conservation of mass/matter?
2. How does it apply to chemical reactions? (incorporate the terms reactants and
products)
3. What do you think it means to have a “balanced” equation? What is being
balanced in the equation?
Return to the main meeting for check back feedback.
Getting Started
1. Go to the PhET simulation
2. Click on the Introduction module
Part 1 – Explore the Simulation
1. How do you make this simulation “work”? What do you have to do?
2. What options can you change in the simulation?
3. What is the purpose of the balance scales and bar charts in the simulation?
Set the simulation to “Make Ammonia” and turn on the “Scales” tool.
4. The number placed in front of a formula is called a coefficient. Change the
coefficient in front of N2 to 1. What happens to the nitrogen scale?
5. Change the coefficient in front of the NH3 to 1. What happens to the nitrogen
scale? What happens to the hydrogen scale?
6. What needs to be done to balance the nitrogen and hydrogen scales?
7. How does the simulation let you know you have a balanced equation?
Part 2 – Balance the Equations
Adjust the coefficients to make balanced equations.
Action
Balanced Equation (fill
in the coefficients)
Draw the particle
view of the
equation
Note the steps you
took to make the
equation balanced
Make
Ammonia
____ N2 + ____ H2 
____ NH3
Separate
Water
___ H2O  ___ H2 +
___ O2
Combust
Methane
___ CH4 + ___ O2

___ CO2 + ___ H2O
2. In each of the following items above a different verb was used. Based on the
reaction how would you define the following verbs?
Word
My definition
Make
Separate
Combust
3. Why can we adjust coefficients when balancing chemical equations but not
subscripts?
4. If you had to explain to a friend how to balance a chemical equation, what
would you say to them?
Return to the main meeting for check back feedback.
Part 3 – Game
Switch to the game module
Play through the levels of the game with your group. Take turns balancing the
equations. Be sure to narrate your thinking as you balance and note the different
strategies you use. Ask and answer questions of your groupmates as needed.
Record your score for each of the levels in the balancing game:
Score
Level 1
/ 10
Level 2
/10
Level 3
/ 10
Concept Review
1. In the simulation, were you able to use non-integer numbers (like ½ or 0.43)
for the coefficients in a balanced equation? Why do you think this is?
2. If you were balancing an equation containing the oxygen, which of the following
would be correct representations of oxygen and its coefficient?
☐ ½O2
☐ O2
☐ 3O2
☐ 6O2
☐ 3O
☐ 5O3
3. What do you have to do to the coefficients of equation I below to get to
equation II?
I.
2 SnO2 + 4 H2  2 Sn + 4 H2O
II.
SnO2 + 2 H2 
Sn + 2 H2O
a) Both equation I and II are balanced, but equation II is the correct way to write
the balanced equation. Why do you think this is?
b) Can you divide equation II by another factor and still have it be correct? Why
or why not?
Summarize
1. What are the basic steps for balancing an equation?
2. What two things should you check before deciding an equation is balanced?
Return to the main meeting for check back feedback.