chapter 5 review Flashcards
system
the part of the universe chosen to study
surroundings
the rest of the universe
open systems
freely exchanges energy AND matter with its surroundings
closed system
can exchange energy, but NOT matter with is surroundings
isolated system
cannot exchange energy OR matter with its surroundings
kinetic energy
the energy of a MOVING object (includes thermal energy-molecular motion)
potential energy
energy resulting from condition, position, or composition (includes chemical energy- potential energy stored in bonds)
the first law of thermodynamics
energy can be converted from one form to another, but cannot be created or destroyed
internal energy of a system (U or E)
sum of all the potential and kinetic energies in the system
ΔU=
q (heat) + w (work)
ΔU isolated=
0
ΔU system =
-ΔU surroundings
system to surroundings
q and w (-)
surroundings to system
q and w (+)
heat
the transfer of thermal energy between a system and surroundings due to temperature difference
1 cal=
4.184 J
(P-V) pressure-volume work
work involved in the expansion or compression of gas
w (work)=
-PextΔV
negative external pressure times the change in volume
how can you tell if P-V work has happened
conceptually= change of gas in a chemical reaction
ex) 2C2H6(s) + 7O2(g) —> 6H2O(l) + 4CO2 (g)
there were 7 moles of gas and then it became four moles of gas
visually= the piston moves
heat capacity(C)=
q/ΔT
q=
mcΔT
solid to liquid
melting or fusion
liquid to gas
evaporation or vaporization
enthalpy(H)
the change in the energy of a system at constant pressure, sum of the change in internal energy and the P-V product
