Thermochemistry (Chang) Flashcards
Energy
Capacity to do work
Work
Directed energy change resulting from a process
Radiant energy/ solar energy
Comes from the sun; Earth’s primary energy source
Thermal energy
Energy associated with random motion of atoms and molecules
Kinetic energy
Energy produced by a moving object
Chemical energy
Stored within the structural units of chemical substances
Potential energy
Energy available by virtue of an object’s position
*Chemical energy can be considered as form of potential energy because it is associated with relative positions and arrangements of atoms within a given substance
Law of conservation of energy
Total quantity of energy in the universe is assumed constant
Heat
Transfer of thermal energy between two bodies that are at different temperatures (hot to cold)
Thermochemistry
-study of heat change in chemical reactions
System
Specific part of the universe that is of interest to us
Surroundings
-the rest of the universe outside the system
Open system
Can exchange mass and energy with its surroundings
Closed system
Allows the transfer of energy (heat) but not mass
Isolated system
-totally insulated container
-does not allow the transfer of either mass or energy
Exothermic process
-any process that gives off heat; transfers thermal energy to surroundings
energy products < energy reactants
Endothermic process
-heat has to be supplied to the system by the surroundings
energy reactants < energy products
Enthalpy, H
H = E + PV
Enthalpy of reaction ∆H
∆H = Hprod - Hreact