Reaction Rates
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Transcript Reaction Rates
UNIT 7-CHEMICAL REACTONS
RATES OF
REACTIONS
Collision Theory
Reaction
rate depends
on the collisions
between reacting
particles.
Successful
collisions occur
if the particles...
collide with each other
have the correct orientation
have enough kinetic energy
to break bonds
Activation Energy
(Ea):
minimum energy
required for a
reaction to occur
Activation Energy
Low
Ea =
faster
reaction rate
Ea
High
Ea =
slower
reaction rate
?
EXOTHERMIC
Heat energy
released
2H2(l) + O2(l) 2H2O(g) + energy
ENDOTHERMIC
Heat
energy
absorbed
2Al2O3 + energy 4Al + 3O2
Factors Affecting Rxn Rate
1. Surface Area (SA)
high SA = fast reaction rate
more opportunities for
collisions
Increase surface area by…
- using smaller particles
- dissolving in water
How can you make sugar
cubes dissolve faster?
2. Concentration
high conc. = fast rxn rate
more opportunities for
collisions
3. Temperature
high temp = fast rxn rate
high KE
-fast-moving particles
-more likely to reach
activation energy
Which of these will sugar
dissolve faster in?
4. Catalyst
substance that increases rxn
rate without being consumed
(used up) in the rxn
lowers the activation energy