I.
Thermochemistry
A. The study of the transfer of energy as heat that accompany chemical reactions and
physical changes
1. Adding/Breaking bonds
B. Enthalpy
1. Energy flow as heat
2. Represented by a capital H
3. ΔH
4. Change
a) Final-Initial
C. Laws of Thermodynamics (3)
1. Law #1
a) Energy cannot be created or destroyed, just transferred or
transformed
b) Law of Conservation of Energy
c) Key terms
(1) Joule(J)
(a) The unit for heat as well as all other forms of
energy
(2) Heat
(a) Can be thought of as the energy between samples of
matter because of a difference in their temperatures
(3) Temperature
(a) The measure of the average kinetic energy of the
particles in a sample of matter
(b) Warmer = zipping/moving faster/higher energy
(c)
(4) Exothermic vs. Endothermic
(a) Exothermic
(i)
Out to system
(b) Endothermic
(i)
In
(c) Which direction does the energy (heat) flow in each
case?
(i)
High to low
(5) Calorimetry
(a) The energy absorbed or released as heat in a
chemical or physical change is measure in a
calorimeter
(6) Two Types
(a) Coffee Cup vs. Bomb
(i)
In coffee cup (the more common), known
quantities of reactants are sealed in a
reaction chamber, which is immersed in a
known quantity of water in an insulated
vessel
(ii) The energy absorbed during the reaction is
equal to the energy absorbed by the known
quantity of water
(iii)
The amount of energy is determined from
the temperature change of the known mass
of surrounding water
(iv)
The quantity of energy transferred as heat
during a temperature change depends on the
nature on
(a) What substance
(b) How much of the substance
(c) How much of change
(b) Formula
(i)
q = c * m * Δt
(a) q is energy lost of gain (+ or -)
(i)
Negative=losing energy to
environment
(ii) Exo
(iii)
Positive
(iv)
endo
(b) m is mass in grams of material
(c) Δt the difference between initial and
final temperatures in C
(d) C is specific heat. This is the amount
of energy required to raise the
temperature of one gram of
substance by one degree Celsius.
Final -Initial. Unkown.
(j/g*C)aserr6t