1. An athlete “burning” calories
7.4 Reaction Rates
Key Concepts
What does a reaction rate tell you?
What factors cause reaction
rates to change?
An athlete “burning” calories

2. A much ____________ way of releasing the energy is to burn
The banana in the photo is providing the cyclist with about 100 ___________ of energy.
The energy from the banana is _____________ during a series of chemical reactions that occur inside your ___________.
A much ____________ way of
releasing the energy is to burn
the banana ___________ the
body during a combustion
reaction
Calories
released
body
faster
outside

3. Reactions Over Time
The progress of any chemical reaction can be measured over ________
A reaction ________ is the rate at which reactants change into ______________ over time
Reaction rates tell you how ________ a reaction is going
time
rate
products
fast

4. Factors that affect reaction rate include…
__________________
Activation Energy
Temperature
Surface Area
Stirring
Concentration
Catalysts

5. Activation Energy
For a reaction to occur between two substances, particles of those substances must ___________ with enough _______ to cause a change to take place
The amount of energy needed when the particles collide is called _____________ _____________
It is kind of like a small _______ that all reactions need
For example, ____________ and ___________ molecules can react to produce ___________ and large amounts of ______________
2H O H2O energy
collide
force
activation
energy
“push”
hydrogen
oxygen
small
water

6. 2H O H2O energy
Oxygen and hydrogen gas, however, can exist in the same container for ________ without reacting
The reaction will not begin until enough activation _________ is provided to start the reaction
years
energy

7. Temperature
Most reactions go faster at __________ temperatures because an increase in temperature…
increases the ____________ of particles
Increases their likelihood of ____________
Example…
Food _________ quickly at higher temperatures but remains fresh longer when _________ or _______________
higher
speed
colliding
spoils
cold
frozen

8. Surface Area
The ______________ the particle size of a given mass, the _____________ is its surface area.
Think of a newspaper…will a newspaper cover more area folded together OR as separate smaller sheets?
smaller
larger
as separate, smaller sheets

9. The rate of combustion was very ____________ due to the small
Increased surface area increases ________________ that involve reacting particles.
This fire was a combustion reaction between grain ___________ and oxygen.
The rate of combustion was very
____________ due to the small
particle size of the grain dust.
collisions
dust
rapid

10. Which picture below shows a higher concentration of particles?
The ____________ of substance present in a certain ___________ is called the concentration of the substance
Which picture below shows a higher concentration of particles?
amount
volume
5 particles
10 particles
10 particles

11. Increasing the concentration of a __________ will speed up a reaction because the particles are _________ together and will ___________ more often
reactant
closer
collide

12. Stirring reactants increases their _________________ to each other.
In a washing machine, particles of detergent react with particles of the _____________ on clothes.
A washing machine ____________ up the reaction by stirring the contents back and forth.
exposure
stains
speeds

13. In a chemical equation, a catalyst may be written…
Catalysts
A catalyst is a substance that ________ up the rate of a reaction without being _______ or _______ up by the reaction
In a chemical equation, a catalyst may be written…
_________ the arrow
2H2O2  2H2O + O2
or before ____ after an arrow to show that it has not changed
2H2O2 + MnO2  2H2O + O2 + MnO2
speeds
changed
used
above
More common!
MnO2
and

14. A catalyst speeds up a chemical reaction by ___________ the activation energy needed to start the reaction
lowering

15. Why is reaction rate important?
Chemical engineers and industries wish to produce their products ______________
The faster the rate, the ______ product that can be made
Food scientists are also interested in ________ down the reactions that cause food to spoil
efficiently
more
slowing

16. Review Question 1 What is activation energy?
The energy required to start a reaction

17. Review Question 2
Predict how the following factors will affect the rate of a reaction…
Increasing temperature
Decreasing concentration
Adding a catalyst
Stirring two substances
Speed up
Slow down
Speed up
Speed up