Flashcards in Thermodynamics Exam 1 Deck (34)
The part of the universe chosen for study
Anything that is not defined as the system
Line or surface that separates the system and surroundings
Composed of both the system and surroundings
3 types of systems
Open: exchange of energy and matter can occur across the boundary.
Closed: exchange of energy that can occur across the boundary
Ex: cup with lid
Isolated: no exchange occurs across boundary
Kinetic energy (eK)
Translational motion of an object causing energy/energy of a moving object. (V and T)
eK = 1/2 mu^2
Potential energy (PE)
Energy due to composition, position, or condition. Stored energy that has potential to do work. (Condition(state), position(height), composition(bond, atom))
Associated with random molecular motion (eg: frictional heating). It is proportional to both the temperature of the system and the number of particles (N) in the system. (Collisions)
SI united of joules and Newton’s
J = Nm = kg(m^2/s^2)
N = kg(m/s^2)
capacity to do work or produce heat
force (F) acting over distance (d). W=Fd, V change, or volume change (-P(delta V))
energy transfer between an open or closed system and its surroundings because of a temperature difference between the two.
equation for heat
heat = q = mCpT
Law of conversation of energy
energy is not created or destroyed
q > 0
heat is absorbed by the system. heat enters the system. endothermic (+)
q < 0
heat evolves from the system. heat leaves the system. exothermic(-)
1 food calorie
isolated system at constant volume; highly exothermic reactions occur.
energy associated with bonds and intermolecular attraction or repulsion. Potential energy of a system associated with chemistry.
heat of reaction (rxn)
quantity of heat exchanged between the system and surroundings during a chemical reaction. Determined by calorimeters. (energy of reaction)
coffee cup calorimeter
at constant pressure and commonly used for solutions. there may be numerous sources of q.
pressure-volume work (w)
chemical reactions that involve work. if gas is released as a product of a reaction, the gas could exert a force on an external object by pushing it, thereby doing work.
1 L atm is how many Joules?
First Law of Thermodynamics
Law of conservation of energy, stating that the energy of the universe is constant. This energy is called the total or internal energy (U) which includes both potential and kinetic energy.
in an isolated system, what is q and w?
0; bc of no transfer of energy
any property that only depends on the current state of the system. the way or path is not relevant. (ex: T,P,V,m,U)
function involves any property that does depend on the pathway by which the current state of the system was obtained. (ex: q and w)
Isothermal conditions for ideal gas
T = 0 and U = 0
Change in Enthalpy
Delta H which is heat at constant pressure. (no T change)
Equation: delta H = delta U + (P)(delta V)
(Reaction, phase change, mixing solutions, U - w)
Measure of the kinetic energy of the system (eK)
Internal Energy (U)
total amount of energy contained within the system boundary (eK, PE)
technique used to find delta H for a given overall reaction when there is a series of simultaneous reactions each having a given delta H.
Simultaneous reactions: sum up to the overall reaction.
Intermediates: appear in the sim rxns but not in the overall reaction.
Standard enthalpy of formation (delta Hf)
change in enthalpy that accompanies the formation of 1 mole of a compound from its elements with all substances in their standard states at 25C. (Elemental form)
Equation: delta H = (sum of (prod moles)(delta H of prod))-(sum of(reactant moles)(delta H of reactants))