Unit 7:
Kinetics and Thermodynamics
Cartoon courtesy of
NearingZero.net
Heat is the energy that is
transferred from one object to
another because of a temperature
difference. The direction of heat
transfer is always from a hotter
object to a colder object.
Thermal equilibrium is reached
when two or more objects in
contact with one another reach the
same temperature.
Heat (Enthalpy) Change
The amount of heat energy released or
absorbed during a process.
Endothermic:
Processes in which energy is absorbed as
it proceeds, and surroundings become
colder
Exothermic:
Processes in which energy is released as
it proceeds, and surroundings become
warmer
You have water at 25°C. You dissolve
ammonium acetate, NH4C2H4O2, in the
water and find the temperature decreases
to 15°C.
Is T positive or negative?
Is heat energy transferring from the
solution to the environment or from the
environment to the solution?
Is the process an exothermic or
endothermic process?
System: The chunk of
the universe being
studied (i.e., a water
molecule, a beaker of
solution, a campfire).
Surroundings:
Everything “outside” the
system.
Heat describes the process of
energy transfer. Heat is not a
“thing” (a noun).
Energy is a measurement of
the capacity of a system to do
work or to transfer heat.
Internal energy is associated
with the degree of motion of
atoms. Heat transfer changes
the internal energy of a system.
Units for Measuring Heat
The Joule is the SI system unit for
measuring heat:
kg  m
1 J  N m 
2
s
2
The calorie is the heat required to raise
the temperature of 1 gram of water by
1 Celsius degree
1calorie  4.18 Joules
A Bomb Calorimeter
A Cheaper
Calorimeter
Calorimetry is the measurement
of the amount of heat
transferred.
The temperature rise of water is
a measure of the amount of heat
transferred from a chemical
change such as a fire.
Calorie: The amount of heat
needed to raise the temperature of
one gram of water by one degree
Celsius.
Specific heat capacity of water
is the conversion factor between
calories, grams, and temperature
change. For water, the conversion
factor is 1 calorie/1 gram – 1°C.
Specific Heat
The amount of heat
required to raise the
temperature of one
gram of substance by
one degree Celsius.
Calculations Involving Specific Heat
q
c  
m T
p
OR
q  c m  T
p
cp = Specific Heat
q = Heat lost or gained
T = Temperature change
m = Mass
Table of Specific Heats
Temperature is a measure of the average
motion, or kinetic energy, of the atoms and
molecules in a substance.
Heat is a measure of the total motion of all the
atoms and molecules in a system. More heat is
required to raise the temperature as the mass of
the substances in the system is increased. The
heat required is also specific to the substances,
and is called the specific heat.
•Latent heat is the heat associated with a
phase change and is measured in cal/g.
Latent Heat of Phase Change
Molar Heat of Fusion
The energy that must be absorbed in
order to convert one mole of solid to
liquid at its melting point.
Molar Heat of Solidification
The energy that must be removed in
order to convert one mole of liquid to
solid at its freezing point.
Latent Heat of Phase Change #2
Molar Heat of Vaporization
The energy that must be absorbed in
order to convert one mole of liquid to
gas at its boiling point.
Molar Heat of Condensation
The energy that must be removed in
order to convert one mole of gas to
liquid at its condensation point.
Latent Heat – Sample Problem
Problem: The molar heat of fusion of water is
6.009 kJ/mol. How much energy is needed to convert
60 grams of ice at 0C to liquid water at0C?
60 g H 2O 1 mol H 2O 6.009 kJ
 20.00 kiloJoules
18.02 g H 2O 1 mol
Mass
of ice
Molar
Mass of
water
Heat
of
fusion
Heat of Solution
The Heat of Solution is the amount of heat
energy absorbed (endothermic) or released
(exothermic) when a specific amount of
solute dissolves in a solvent.
Substance
Heat of Solution
(kJ/mol)
NaOH
-44.51
NH4NO3
+25.69
KNO3
+34.89
HCl
-74.84