What does temperature measure?
What does pressure measure?
Thermochemistry
 Heat changes that occur during a chemical reaction
 Energy- the capacity for doing work or supplying heat
 Energy is weightless, colorless, and odorless
 Energy that is stored in the bonds of chemical
substances is called chemical potential energy.
(Example: gasoline)
What is Work and Heat?
 Work- when a force is used to move an object
 Heat- energy that is transferred from one object to
another
 Through a temperature change
 Neither senses nor instruments can detect heat; only
changes in heat can be detected
 Heat flows from warm to cold until equilibrium is
reached
Key terms for describing the flow of
energy
 System- part of the
universe you are
interested in
Surroundings
 Surroundingseverything else in the
universe
System
 Universe- the system
and the surroundings
The Universe is Everything
Endothermic
 When heat flows into a
system from the
surroundings the
process is called
endothermic
 +q
Exothermic
 When heat flows out of
a system into the
surroundings the
process is called
exothermic
 -q
What is a calorie?
 The quantity of heat
required to raise one (1)
gram of water one (1) C
 The unit that we will be
using that is the SI system
of measurement for heat is
the joule
 1 joule = 0.2390 calories
 1 calorie = 4.184 joules
Heat Capacity
 The amount of heat
needed to raise the
temperature of
substance 1 C
 Heat capacity depends
on the composition and
the mass of the
substance
Specific Heat Capacity
 The amount of heat it takes





to raise 1 gram of a
substance 1 C
We can determine the heat
capacity using the equation
C = Specific Heat
(J/g  C or cal/g  C)
q = heat (J or cal)
m = mass (g)
T = Tfinal – Tinitial (C)
q
Cp 
m  T
Example
 When 400 J of heat is added




to 4.0 grams of olive oil at
20C, the temperature
increases to 60C. What is
the specific heat of olive oil?
C=?
q = 400 J
m = 4.0 g
T = Tfinal – Tinitial = 60C –
20C = 40 C
q
C
m  T
400 J
C
4.0 g  40C
J
C  2.5
g  C
Another Example
 How much heat is required




to raise the temperature of
200.0 g of mercury 50 C?
The specific heat of mercury
is 0.15 J/g  C.
C = 0.15 J/g  C
q=?
m = 200.0 g
T = 50 C
q
C
m  T
q  C  m  T
J
q  0.15
 200.0 g  50C
g  C
q  1500 J