Unit 7: Thermochemistry Flashcards
define energy
the capacity to do work or transfer heat
what is the equation for change in energy (delta energy)
delta E = Efinal - Einitial = q +w
what is 1 calorie in joules
4.184 J
define system and surroundings
- system: object(s) being studied
- surroundings: everything outside of the system
describe what it means when the change in energy is <0
- initial energy is higher than final energy
- energy of reactants higher than energy of products
- energy is lost to surroundings
describe what it means when the change in energy is >0
- final energy is higher than initial energy
- energy of products is higher than energy of reactants
- energy gained from surroundings
define state functions
- depend on initial and final states of a system
- uppercase variables: V, E, P, T
define path functions
- depend on the path a system takes to get from the initial to the final state
- lowercase variables: q, w, t, d
which type of function is easier to measure
state functions
define internal energy
energy contained within a system
define kinetic energy
energy associated with motion
what are the three types of kinetic energy
- translation
- vibration
- rotation
define potential energy
energy associated with position
what are the two types of potential energy
- chemical bonds
- intermolecular forces
what is the order of phase states from lowest energy to highest energy
- lowest energy: solid
- middle energy: liquid
- highest energy: gas
is energy absorbed or released when water evaporates
- liquid to gas: lower energy to higher energy
- energy of products (gas) greater than energy of reactants (liquid)
- energy is absorbed
define specific heat (C)
amount of heat required to raise the temperature of ONE GRAM of a substance one degree celsius
define molar heat capacity (Cm)
amount of heat required to raise the temperature of ONE MOLE of a substance one degree celsius
does water have an unusually high or low specific heat
high - 4.814 J/gC
define the variables in q=mCAT
- q = heat (J)
- m = mass (g)
- C = specific heat (J/gC)
- AT = temperature change, final-initial (C)
how is the heat of the system related to the heat of the surroundings
- q(system) = -q(surroundings)
- heat from system is equal and opposite of heat from surroundings
- system with either gain or lose heat while the surroundings do the other until the temperatures of both are equal
define calorimetry
the measurement of heat changes
describe the equation used in calorimetry
- q(reaction) = -q(calorimeter)
- q(reaction) = -q(water)
- q(reaction) = -mCAT(water)
what are two types of calorimeteres
- coffee cup calorimeter
- bomb calorimeter