Chemistry Chapter 5 Thermochemistry
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Flashcardsenergy
the capacity to do work or to transfer heat
energy cannot be created or destroyed, it can only be converted from one form to another
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44 Terms
energy
the capacity to do work or to transfer heat
energy cannot be created or destroyed, it can only be converted from one form to another
two types of energy
potential and kinetic
kinetic energy
energy due to position in space or composition
potential energy
energy because of motion and is dependent on the mass and velocity of an object
thermal energy
type of kenetic energy associated with heat in matter
temperature
a measurement of the average thermal energy of matter in a system
system
an object or matter that is the point of study
surroundings
everything outside of a system
open system
a system that can freely exchange both matter and energy with their surroundings
closed system
a type of system that can freely exchange energy with their surroundings but not matter
isolated system
a type of system that cannot exchange either matter or energy with their surroundings
heat (q)
the transfer of energy from warmer objects to cooler objects due to a temperature difference
thermal equilibrium
will always flow from the object with the higher temperature to the object with a lower temperature until both objects are at the same temperature
calorie
the amount of energy that is required to increase the temperature of 1.00g of water by 1 degree C
exothermic process
a process in which a system releases energy in the form of heat to its surroundings (heat is negative)
endothermic process
a process in which a system absorbs energy in the form of heat from its surroundings (heat is positive)
work
describes a force acting over a distance
internal energy
describes the potential energy and kinetic of all particles in a system
equation for internal energy of a system
delta E = q + w
if work is positive
we would say work is being done on the system
if work is negative
work is being done by the system
enthalpy (delta H)
the internal energy of a system plus the products of its pressure times the volume
formula for delta H
delta H= delta E + delta PV
delta D= q
state function
a property that depends ONLY on the initial and final states
the path taken from the initial to the final state does not matter
path or process function
the ENTIRE pathway is considered getting from the initial to the final state
heat capacity (C)
the amount of heat that is required to change the temperature of a substance by 1 degree C
formula for heat capacity
C= q/delta T
formula for delta T
delta T= Tfinal-Tinitial
specific heat capacity
the amount of heat that is required to raise the temperature of 1 gram of a substance by 1 degree C
molar heat capacity
the amount of heat that is required to raise the temperature of 1 mole of a substance by 1 degree C
relationship between heat capacity and energy
the higher the heat capacity the more energy required to change its temperature
thermal equilibrium equation
q1 + q2 = 0
caliometery
a technique used to measure heat that is absorbed or evolved in a chemical reaction or physical process
constant pressure (coffee cup) calorimetry
a type of calorimeter used to determine the change in enthalpy for some chemical reaction or process
coffee cup calorimeter equation
q reaction - q calorimeter = 0
what happens when the temperature of the calorimeter increases
a negative (exothermic) heat of reaction
what happens when the temperature of the calorimeter decreases
a positive (endothermic) heat of reaction
constant volume (bomb) calorimeter
is used to determine the change in energy for some chemical process in which volume is held constant but not pressure (must consider heat capacity in our calculations)
in bomb calorimetry what does q calorimeter equal
q cal = (Ccal)(DeltaT)
hess law
states that if a reaction can be represented as the sum of two or more reactions, then the enthalpy of reaction for the overall process will be equal to the sum of the deltaHr values of those reactions
standard enthalpy of formation (deltaHf)
the enthalpy change for the formation of one mole of a compound directly from its component elements
standard enthalpy of formation for an element in its standard state
is always zero
calculation for the enthalpy change for a reaction under standard conditions
deltaHr= products - reactants
Note 
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