Name: __________________________________
Period: ___
Activation Energy Simulation
URL: http://phet.colorado.edu/en/simulation/reversible-reactions
Instructions:
1) Match the words to the parts of the simulation: products, reactants, activation energy.
a. Left side of curve: _________________
b. Right side of curve: _________________
c. Ruler in the middle: ________________
2) What do the heights of the left side, right side, and ruler represent?
3) Set the simulation to the following values:
 Left side to 20, right side to 15, middle to 25
 PAUSE the simulation (bottom middle)
 Start timer (it won’t start until you hit play)
 Add 50 “A” using the “Molecules in Chamber” in the upper right corner
a. Are the “A” you added reactants or products? (Where did the ball/molecule appear?)
b. Before starting the simulation, predict where most of the molecules will end up over time.
c. Click PLAY now and run the simulation. Pause it and record your values at the given times below:
Time
0
60
120
180
240
Left Side
Right Side
d. Create a line graph from your data in 3c. Make sure to graph both the amount of products and reactants.
Amount of
molecule
Time
e. What happened over time? Was your prediction correct?
f. If you ran the simulation for a whole day, what do you think the simulation would look like?
g. Did any of the molecules go back from B to A?
4) Reset the simulation and change it to these new values:
 Left side to 45, right side to 15, middle to 50
 PAUSE the simulation (bottom middle)
 Start timer (it won’t start until you hit play)
 Add 50 “A” using the “Molecules in Chamber” in the upper right corner
a. Before you start the simulation, what is your prediction?
b. Now run the simulation and record your data:
Time
Left Side
Right Side
0
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60
120
180
240
c. Which side has more potential energy? Which has more kinetic energy?
d. What happened to the total temperature as time went on?
5) Reset the simulation and change it to these new values:
 Leave the heights the same as in question #4
 PAUSE the simulation (bottom middle)
 Start timer (it won’t start until you hit play)
 Add 50 “A” using the “Molecules in Chamber” in the upper right corner
 Set “Temperature of New Particles (K)” to 1000
a. Run the simulation and record your data:
Time
Left Side
Right Side
0
60
120
180
240
b. What does adding heat do to the experiment?
6) Design your own experiment and record the settings below:
a. Ruler height: ____
d. Starting molecules A: ___
b. Left side: ____
e. Starting molecules B: ___
c. Right side: ____
f. Temperature of new particles: ____
g. What is your prediction with your new settings?
h. Run the simulation and record your data.
Time
Left Side
Right Side
0
60
120
180
240
i. Was your prediction correct? Explain based on your data.
Analysis:
1) What does moving from the left side to the right side represent in this simulation?
2) How did the height of the middle “ruler” affect the rate at which molecules moved from one side to the
other?
3) How did the temperature of the added molecules affect the rate at which molecules moved from one side to
the other?
4) We usually show chemical reactions with a single arrow  pointing in one direction. Based on this
simulation, do you think that means that the reaction can ONLY go that direction, or that it PREFERS to go
that direction? Explain.