Thermochemistry Chapter (Lecture 1) 9 Terms Flashcards
Internal Energy
A microscopic energy contains in a substance. Formula: Internal Energy (U)= Thermal Energy + Chemical Energy
Thermal Energy
Energy that results in temperature.
TE= KE (Kinetic energy)
Ex: Higher T= Faster Molecular Motion
Chemical Energy
Chem energy = Chem bonds
As chemical bonds break apart the chemical energy increases.
A physical change occurs (State of matter changes)
Intermolecular attractions
Potential Energy that resides in Chemical energy
System and Surrounding
Universe = System + Surrounding
System: Part of the universe chosen for Study
Surrounding: Part of the universe outside system
What is system and surrounding connected by?
Matter: Flow of molecules across boundaries
Heat: Transfer of energy form high T to low T
Work
Force acting through a distance
Open systems
Systems that can exchange matter with surroundings like heat of work. Ex: Water vapor escaping from beaker
Closed System
System does not allow flow of matter within surrounding. Ex: sealed flask or balloon with Helium. (Balloon expands; gas inside work on surrounding and surroundings lose energy
OR heat will flow of balloon if the outside temp is lower
Isolated System
Cannot exchange any heat, work or matter with surrounding.
Heat
(q) Internal Energy being transferred between a system and surrounding.
Heat flows from hot to cold Ta>Tb
Calorie
Quantity of heat required to change temp of one gram of water by one-degree Celcius
Conversion from Joule to Calorie
1 cal = 4.184 j
Heat and law of Conservation of Energy
Heat gained by system = is lost by surroundings
Positive: Heat gained in system
Negative: Heat is lost in system
q system = - q surr
Heat flows from surrounding to the system.
q system (+) q surr (-)
Heat that flows from system to surrounding
q system (-) q surr (+)
Heat Capacity
Capacity C = quantity of heat required to change the temperature of substance by 1 C
C= q/ Change in Temperature (J/ C)
Extensive property
units: moles and grams
Ex: mass, volume, heat capacity (as more mass and volume is added they will increase)
Proportional to system size
Intensive property
Does not depend on system size. Ex: Temp, Pressure, density
Specific Heat Capacity (per gram)
Divided by system size to get intensive property
Formula: Csp = Heat supplied/(Temp rise) x (mass) = (q/change in Temp x grams) = (J/ C x g)
Molar Heat Capacity (mer molar)
J/ C x mol
Heat supplied
q= mCsp (change in Temperature)
Specific heat values in metals
Some have different heat capacities such as Iron having 0.449 less than ICE with 2.11. Change in property can change specific heat values.
Enthalpy Formula
H = U + PV
Work formula
w= -P(Vf-Vi)
Ef-Ei =
Qp x -P (Vf-Vi)
Work being done by the system on surrounding
w<0
Work being done by surrounding onto the system.
w>0
