chapter 7: chemical energy Flashcards
what is thermodynamics
the study of energy and its transformations
what is thermochemistry
relationship between chemical reactions and energy changes involving heat
what is energy
the ability (or capacity) to do work or transfer heat.
what is work
Energy used to cause
an object that has mass
to move
what is heat
Energy used to cause
the temp of an object
to rise
what is force
any kind of push or pull exerted on an object
what is the formula for force
f = m x g
what does g stand for
acceleration due to gravity; 9.8 m/s^2
what is the magnitude of work formula
w = F x d = m x g x d d = distance m = mass F = force g = gravity
what is another name for heat
thermal energy
what direction does heat flow
warmer objects to cooler objects
what are some characteristcs of heat and work
- energy is being exchanged between two objects
- energy can flow into or out of the subject studied
- dont exist before or after the state of change
what types of energy are there
potential and kinetic
what is electrical energy
KE associated w/ flow of electrical charge
what is heat or thermal enrgy
KE associated w/ molecular motion
what is light or radiant energy
KE associated with energy transitions in an atom
what is nuclear energy
PE in the nucleus of atoms
what is chemical energy
PE due to the structure of the atoms
what is kinetic energy
energy that is being transferred (motion)
what is the kinetic energy formula
KE = 1/2mv^2
what does KE depend on
the mass and speed of the object
do atoms and molecules possess KE
yes
what is potential energy
energy that is stored in an object
when does PE arise
no force operating on the on
what does PE depend on
mass, height, the gravitational
what is the formula for PE
m x g x h
what is the unit for energy
Joule (J)
who was the energy SI unit named after
James Joule
what does 1 joule equal
1 kgm^2/ s^2
what is a non-SI unit that is still used
calorie (cal)
how many joules does one calorie equal
4.184 J
what is the value of the nutritional calorie
1000 cal (1kcal)
what is the system
included the molecules we want to study
what are the surroundings
everything else
what is temperature
measure of the kinetic energy,
thermal energy, within a sample of mater.
what is thermal equilibrium
the flow of heat from high temp to low temp until both objects reach the same temp
what does endothermic mean
heat is absorbed by the system from the surroundings
what does exothermic mean
eat is released by the system to
the surroundings,
what is the first law of thermodynamics
law of the
conservation of energy.
the total energy of the universe it….
constant
if the system loses energy…
it must be gained by the surroundings
what are state functions
values that depend on the state of the substance, and not on how that state was reached.
is delta E a state function
yes bc it depends on the specific amounts of q and w
what is an example of a state function
water reached room temp from both directions
are q and w state functions
no bc they are forms of energy in transit, don’t exist before or after the change of the state
what does delta E equal
q + w
when does E increase
when heat is added to a system or work is done on a system
what does q represent
heat
what does w represent
work
what happens when q is +
system gains thermal energy
what happens when q is -
system loses thermal energy
what happens when w is +
work done on the system
what happens when w is -
work done BY the system
when do most of the chemical and physical changes occur
occur at constant atmospheric pressure
what is the formula for pressure-work volume
w = -(P)(change in volume)
what is the change in volume
Vfinal - Vinitial
when gases expand what happens to the volume and work
V = + w = -
what is enthalpy
heat flow; s defined as the internal energy plus
the product of pressure and volume:
what is the formula for enthalpy
H = E +PV
what is the formula for enthalpy when system changes at constant pressure, the
change in enthalpy,
deltaH = q
delta H is positive
endothermic
delta H is negative
exothermic
what is the formula for enthalpy of a reaction
deltaH = Hproducts - H reactants
what is the delta H called
enthalpy of reactionb
what are the rules of enthalpy
1.) extensive property
what is heat capacity
amount of energy required to raise the temp. of a substance by 1 K (1 °C)
what is specific heat capacity
amount of energy required
to raise the temperature of 1 g of
a substance by 1 K (1 °C)
what is molar heat capacity
the heat capacity of one mole of
a substance is called its
what is the formula for heat capacity
Cs = q/ m x deltaT
what is the formula for q
m x Cs x change in temp
what does Cs mean
specific heat
what is calorimetry
measurement of heat flow
what is a calorimeter
device used to measure heat flow
what happens with the heat produced in a calorimetry reaction
the solution absorbs it
what happens to heat in an exothermic reaction
heat is lost by reaction and gained by the solution
what happens to heat in an endothermic reaction
heat is gained by the reaction and lost by the solution
the heat gained by the solution is equal to…
the magnitude of qrxn
what does qsoln =
m x s deltaT = -qrxn
what is the constant pressure formula for metal
mass metal x Cs metal x change temp of metal = mass metal x Cs metal x change temp of metal
what is the second rule of enthalpy
change of heat for a reaction in the forward direction is
equal in magnitude, but opposite in sign, to H
for the reverse reaction
what is the third rule of enthalpy
H for a reaction depends on the state of the
products and the state of the reactants.
