Download Chemical Reaction

Chemical Reaction
Process in which one or
more substances are
changed into one or more
different substances
Examples: burning coal,
rusting, cooking
Chemical Reaction
Beginning & ending substances
have different properties
Atoms are rearranged,
chemical bonds are broken and
new bonds are formed
All reactions involve energy
changes
Chemical Equations
An expression using
symbols & formulas to
represent a chemical
reaction
Chemical Equations
C + O2 CO2 + energy
reactants
yield sign
products
Chemical Equations
Reactants
–Substance(s) that enters
into a chemical reaction
–Left side of the equation
Chemical Equations
Yield sign
–Replaces the equal
sign of an equation
–Shows the direction of
the chemical change
Chemical Equations
Products
–Substance(s) produced
from a reaction
–Right side of the
equation
Law of Conservation of
Mass
Mass remains constant
in a chemical reaction
The number of atoms on
both sides of the equation
remains the same
Law of Conservation of
Mass
Atoms are
rearranged, not
created or destroyed
Balancing equations
Coefficients
–Whole number placed in
front of a symbol or
formula to show the
number of atoms or
molecules involved
Balancing equations
Coefficients
–Coefficient of one is
not written, it is
understood
Balancing equations
Rules to balance an equation
–1. Write out the proper
formulas.
–2. Draw a line down from the
yield sign to separate the
reactants from the products
Balancing equations
Rules to balance an equation
–3. List the atoms found on each
side of the equation in the
same order
–4. Count the number of atoms
on each side of the equation
Balancing equations
Rules to balance an equation
–5. Add coefficients until the
number of atoms on each side
of the equation are equal.
Balancing equations
Examples
H2 + O2
H2O
Balancing equations
Examples
Fe + O2
Fe2O3
Balancing equations
Examples
CrCl3 + H2S
Cr2S3+ HCl
Balancing equations
Examples
P + O2
P2O5
Balancing equations
Examples
BaCl2 + H2SO4
BaSO4 + HCl
Energy in Chem Rxn
Exothermic reaction
–Chemical reaction in
which energy is released
–Examples: burning or
combustion, digestion of
food
Energy in Chem Rxn
Exothermic reaction
–Energy comes from the
bonds in molecules
–Energy of the reactants is
higher than the products
Energy in Chem Rxn
Endothermic reaction
–Chemical reaction in
which energy is absorbed
–Examples: making soap,
photosynthesis
Energy in Chem Rxn
Endothermic reaction
–Energy is absorbed or
stored in the molecules
–Energy of the reactants is
lower than the products
Energy in Chem Rxn
Activation energy
–The amount of energy
needed to start a
chemical reaction
–All reactions require
activation energy
Energy in Chem Rxn
Activation energy
–Exothermic reactions
require a smaller amount
of activation energy than
endothermic reactions
Energy in Chem Rxn
Spontaneous reaction
Takes place with so little
energy than it seems as if no
activation energy is required
Example: battery
Kinetics
Study of reactions
rates
How fast the
reactants turn into
the products
Kinetics
Collision theory
–In order to react,
particles must collide
at the correct angle
and with enough
energy
Kinetics
Collision theory
–Depends on several factors
Concentration- higher the
concentration, the more
particles, the greater the
chances of collisions
Kinetics
Surface area- higher the
surface area, the greater
the number of particles
exposed, the greater the
chances of collision
Kinetics
Temperature- higher the
temperature, the faster
the particles move and
with more energy, the
greater the chances of
collision
Kinetics
Catalysts
Substance that increases the
rate of a reaction but is not
itself changed by the reaction
Can be reused
Produces a lower energy path
for the reaction
Kinetics
Catalysts
–Examples: digestion,
catalytic converters in cars,
enzymes
Kinetics
Catalysts
–Inhibitors
A catalyst that slows down a
reaction
–Example: preservative