Rates of Reactions

BELL RINGER
WATCH THE
VIDEO AND
RECORD

 https://www.youtube.com/watch?v=OttRV

5ykP7A

ESSENTIAL
QUESTION

WHAT IS THE HEAT OF
REACTION (ΔH)?

STANDARD
SC.912.P.10.5

 Use the kinetic-

molecular theory to
describe the behavior
and kinetic energy of a
molecule and compound
during changes in
temperature.

OBJECTIVES

Understand the 5
ways that speed up
a reaction rate and

why

Recognize what 2
things must happen

for a reaction to

happen

ENERGY AND
CHEMICAL
REACTIONS

Chemical Energy – Energy stored in
the chemical bonds of a substance.

Chemical reactions always involve
energy changes.

Making bonds and breaking bonds
involve energy changes

When you add heat energy, molecules
move faster; temperature increases.

• Temperature: a measure of heat,

increase heat, increase temperature

Chemical Potential Energy: stored
energy in chemical bonds

• Depends on the type of atoms and

arrangement

FACTORS THAT
INCREASE REACTION
RATES

Increasing surface area of a
solid reactant

Increasing temperature

Increasing concentration or
pressure of a reactant

Nature of the reactants

Adding a catalyst.

INCREASE SURFACE AREA

Increase surface area of the reactant by crushing solid reactant into smaller pieces.

Ex: Adding sugar to your Hot Tea

INCREASING TEMPERATURE

Increasing temperature increase kinetic energy which: (Learned in Gas Laws)

Breaks forces of attraction

Increases the number and intensity of collisions between reactants

INCREASE CONCENTRATION
OR PRESSURE

An increase in concentration means an increase in the amount of
reactant which will increase in the number of collisions between
the reactants which increases the rate of the reaction.

• An increase in

pressure will also
do the same thing

NATURE OF THE REACTANT

Individual properties of substances also affect reaction rates. Some of the properties in this
category are:

State of matter: Gases react faster than liquids and solids while aqueous tends to react fastest.

Molecular size/Number of bonds: Smaller molecules with less bonds react faster than bigger
molecules with more bonds.

Bond type: Ionic tend to react faster than covalent

Bond strength: Single bonds are easier and faster to break than double or triple bonds.

ADD A CATALYST

Activation Energy-the energy required for a
reaction to start. ALL CHEMICAL REACTIONS
REQUIRE ACTIVATION ENERGY!!!

Catalyst- is a substance that reduces the activation
energy of a reaction and causes the reaction to occur
“faster”. CATALYSTS ARE NOT PART OF THE
REACTION! They are unchanged during the reaction.

Multiple Choice

Increasing the concentration of the reactants will slow down the reaction.

• false 

• true

Multiple Choice

Why does a higher temperature increase the rate of a reaction?

• it increases both the frequency and energy of particle collisions

• it only increases the frequency of particle collisions

• it only increases the energy of particle collisions

• it reduces the activation energy of the reaction

Multiple Choice

What letter represents the activation energy?

• A

• B

• C

• D

Multiple Choice

Why does a higher concentration increase the rate of reaction?

• it increases the amount of reactants

• it lowers the activation energy

• it increases the energy of particle collisions

• it increases the frequency of particle collisions

Multiple Choice

As the frequency of ______________ increases, the rate of reaction increases.

• Time

• Reactions

• Collisions

• Reactants

Multiple Choice

Adding a catalyst ___________ the activation energy.

• Raises

• Lowers

• Doesn't affect

• Inreases

Multiple Choice

The minimum amount of energy needed for colliding particles to react is called

• Chemical Energy

• Kinetic Energy

• Activation Energy

• Potential Energy

Multiple Choice

Powdered sugar has a greater ______ _____ than a solid cube of

sugar.

• Surface Area

• Catalyst

• Temperature

Multiple Choice

Under the collision theory, the particles must collide with  ____ and ____ for a reaction to occur.

• sufficient rate and sufficient energy

• sufficient surface area and correct orientation

• sufficient catalyst and sufficient energy

• sufficent energy and correct orientation

Multiple Choice

Which group of particles shows that increasing surface area increases collisions among particles?

• Left side

• Right side

• Cannot be determined by either picture

Multiple Choice

Smaller particle size allows for a _________ surface area to be exposed for the reaction.

• larger

• smaller

Multiple Choice

Grinding a seltzer tablet into powder increases the rate of reaction due to increased

• concentration

• surface area

• temperature

• reactants

Multiple Choice

Which factors increase the rate of a reaction.

• increasing temperature

• increasing concentration

• increasing surface area

• all of these