Chemistry
Math / Symbols
Energy
The capacity to do work (exerting
force over distance)
Directed energy change resulting
from a process. (not a state
function)
w = -P∆V
P = F/d²
V = d³
- in a vacuum, p=0 and therefore
w=0
Kinetic energy- energy of motion
Radiant energy- solar energy
Thermal energy- energy
associated with random motion of
atoms and molecules; more
movement=more energy
Chemical energy- stored within
structural units of chemical
substances; when chem. reaction
occurs, energy is released,
stored, or converted to another
form of energy
Potential energy- energy available
because of an objects position,
ex: rock on a cliff edge
The total quantity of energy in
the universe is assumed constant;
as energy is used, it converts to
different forms all the time
The transfer of thermal energy
Work
Types of energy:
Law of Conservation of Energy
Heat
Thermochemistry
What is a system?
The 3 types of systems are:
Explain system/surroundings
relationship as it relates to chemical
reactions.
Exothermic process
between two bodies that are at
different temperatures; nearly all
chemical reactions absorb or
produce (release) energy in the
form of heat; q (not a state
function)
the study of heat change in
chemical reactions
The specific part of the universe
that is of interest to us.
Open system- can exchange mass
and energy, usually in the form of
heat with its surroundings (ex:
water in an open container)
Closed system- allows the
transfer of energy(heat), but not
mass (ex: closed container)
Isolated system- does not allow
the transfer of either mass or
energy (ex:insulated, closed
container)
In a chemical reaction, the
reacting mixture would be the
system and the rest of the
universe the surroundings.
Because energy cannot be created
or destroyed, energy lost by the
system must be gained by the
surroundings (exothermic).
Conversely, in some reactions,
heat can be supplied to the
system by the surroundings
(endothermic).
any process that gives off heattransfers energy to the
surroundings
(ex: combustion of hydrogen gas
in oxygen)
2 H₂(g) + O₂(g) → 2 H₂O(l) +
energy
Endothermic process
heat has to be supplied to the
system by the surroundings
(ex: decomposition of mercury
(II) oxide at high temp)
energy + 2 HgO(s) → 2 Hg(l) +
O₂(g)
Thermodynamics
scientific study of the
interconversion of heat and other
kinds of energy
What determines the state of a system?
the values of all relevant
macroscopic properties
(composition, energy,
temperature, pressure, and
volume)
What are state functions?
properties that are determined
by the state of the system,
regardless of how that condition
was achieved
(energy, temperature, pressure,
volume)- when system state
changes, the magnitude of change
in any state function depends only
on the initial and final states of
the system and not on how the
change is accomplished
ex: ∆V = Vf - Vi
Define the First Law of Thermodynamics: energy can be converted from one
form to another, but cannot be
created or destroyed
Explain the two components of a system's Kinetic energy- various types of
molecular motion and the
movement of electrons within
molecules
Potential energy- determined by
attractive interactions between
electrons and nuclei and by
repulsive interactions between
electrons and nuclei in individual
molecules, as well as by
interaction between molecules
What is specific heat? (s)
the amount of heat required to
raise the temperature of one
gram of the substance by 1°C.
-intensive property
What is heat capacity? (C)
the amount of heat required to
raise the temperature of a given
quantity of the substance by one
degree Celcius.
-extensive property
What is the relationship between specific C = ms
internal energy:
heat and heat capacity?
What are the equations for calculating
heat change?
C = heat capacity (J/°C)
m = mass of substance in grams
s = specific heat (J/g ⋅ °C)
q = ms∆t
q = C∆t
(∆t = t(final) - t(initial))
(∆t is the change in the sample's
temp)
(q is the amount of heat released
(-, exothermic) or absorbed (+,
endothermic) in a particular
process)
By;Lama Nasser Al-Zakari.