Thermochemistry Theory Flashcards
What is heat?
form of energy that flows between two samples at different temperatures
always flows from hot to cold
conduction, convection, radiation
What is temperature?
average kinetic energy of molecules
random movement of particles
What is thermal energy?
total heat energy in a substance
What are the (two) laws of thermodynamics?
energy can be converted from one form to another but can’t be created or destroyed
heat flows from hot objects to colder ones until thermal equilibrium is reached
What is potential energy?
energy stored in BONDS within and between molecules
chemical energy (deals with bonds)
originated from the sun (geothermal energy as an exception)
Ep is ABSORBED when bonds BREAK (endothermic)
Ep is RELEASED when breaks FORM (exothermic)
What is kinetic energy?
the energy of motion of ions, atoms, molecules
TEMPERATURE DEPENDENT
E ABSORBED, temp increases
E RELEASED, temp decreases
What is an exothermic process?
energy is RELEASED to its surroundings
ex) cell resp
when H2O mel, you ADD E, so when H2O freezes, you RELEASE E
What is an endothermic process?
energy is absorbed from its surroundings
ex) photosynthesis where E is stored as Ek
anything where you ADD heat
What is heat capacity?
the energy required to raised that amount of substance by one degree Celsius, depends on amt
What is molar heat capacity?
the energy required to raise 1 mole of a substance by 1 degree Celcius
What is specific heat capacity?
the energy require to raise 1 gram of a substance by 1 degree Celcius
How do you calculate kinetic energy (aka heat transfer)?
Ek=mct
What happens in an endothermic reaction?
bonds broken, E absorbed
in delta H notation, delta H is POSITIVE
if incorporated, delta H positive on REACTANT SIDE
down to up
Ep (products) > Ep (reactants)**
What happens in an exothermic reaction?
bonds formed, E released
in delta H notation, delta H is NEGATIVE
if incorporated, delta H positive on PRODUCT SIDE
up to down
Ep (products) < Ep (reactants)**
What is enthalpy?
the total potential energy possessed by a substance (chemical potential energy)
it is a property of a system that reflects its capacity to exchange energy, depends on state and temperature
