ENTERING
PROCEDURE
Make sure that all your pages have been
locked in and locked down into your
Interactive Notebooks for today’s lesson.
Pages have been
convenience. 
numbered
for
your
BELL RINGER
Take a few minutes and jot down some information related to
Potential Energy. 5-6 sentences and at least 1 drawing.
Questions to Consider
• What do you remember about potential Energy from our
previous classes?
• Are there pictures that you associate with this term? If so
draw them.
• How does this term relate to chemical reactions
YOU DO NOT HAVE TO WRITE THE
QUESTIONS
POTENTIAL
ENERGY
DIAGRAMS
TODAY’S OBJECTIVES
• Students will be able to (SWBAT)
calculate enthalpy of a reaction using
potential energy diagrams.
• SWBAT Create and interpret Potential
Energy diagrams for exothermic and
endothermic reactions
• SWBAT identify energy of activation,
effects of a catalyst and PE of Reactants
and Products using potential energy
diagrams.
ENERGY IN ALL OF ITS FORMS.
WHAT CAUSES MOVEMENT?
Rollercoaster Video
DEFINITIONS AND
SYMBOLS
1. Potential energy (PE): the energy stored in a
substance (measured in kJ)
2. PE reactants: Potential energy of the reactants
3. PE products: Potential energy of the products
4. Activation Energy (Ea): Energy needed to make
the reaction go
5. Heat of reaction (∆H): PE products - PE reactants
POTENTIAL ENERGY (PE)- THE
ENERGY STORED IN A SUBSTANCE
∆H = heat of reaction
Activation Energy
(Energy needed
to make the rxn go)
PE reactants
PE products
∆ H = PE products – PE reactants
*If the reaction was reversed*
∆H = heat of reaction
PE products
Activation Energy
(Energy needed
to make the rxn go)
PE reactants
∆ H = PE products – PE reactants
You might
want to
copy this
down
A
B
1. PE reactants? 40 kJ
2. PE Products? 20 kJ
3. Ea forward (find this by subtracting the number at the top of the
hill minus the value for the PE reactants)
100 kJ – 40 kJ = 60 kJ
4. Find ∆Hrxn?
20 kJ – 40 kJ = -20 kJ
+∆H = Endothermic
What is
the heat of
reaction?
∆ H = PE products – PE reactants
∆ H =350 – 200 = 150
kJ
-∆H = EXOTHERMIC
What is the
heat of
reaction?
Which type
of reaction
is more
likely to
happen, fwd
or
backward?
40
10
∆ H = PE products – PE reactants
= -30
∆ H = 10 – 40
kJ
What does adding a catalyst do in a
reaction?
EA without a
catalyst
EA with a
catalyst
•Adding a catalyst
lowers the
activation energy.
•This speeds up the
reaction, but ∆H
remains
unchanged.
Answer: Lowers the activation energy!
Post-lab questions:
1.Was this experiment exothermic or endothermic?
Explain how you know.
2.What was the role of the yeast in this experiment? Do
you think the experiment could have happened without
yeast?
3.What would have happened if a stronger
concentration of hydrogen peroxide had been used?
4.Given your answer to question #1, make a SKETCH of
a potential energy diagram. Make sure your diagram
either matches an exothermic graph or an endothermic
graph. Be sure to label parts of your graph
INDEPENDENT WORK
TIME
Now work on the
Potential Energy
Diagram Worksheets
EXIT SLIP ANSWERS
A. Labeled
Potential energy
Ea
PE
products
B. 412kJ – 2631kJ =
-2219 kJ
C. Exothermic
PE
reactants
Reaction coordinate
Grading Scale
6 = 100
5 = 83
4 = 66
3 = 50
2 = 33
1 = 16
0=0