Thermodynamics Flashcards
Linear expansion=?
Volume expansion=?
Change in L is proportional to L x change in T.
When temperature of a solid increases, the length increases.
Volume exhibits same relationship with T.
First law of thermodynamics=?
change in U=Q-W= (heat into system) - (work out of system)
definition: total energy in the universe can never increase or decrease (conservation of energy)
Amount of heat gained/lost for given change in temp=?
q=mc x change in T. m=mass, c=specific heat
What is the specific heat?
for water?
the amount of heat required to increase the temperature of 1g substance by one degree C or K.
Specific heat of water = 1 cal/(g x K) or 4.184J/(g x K)
Amount of heat gained/lost during a phase change=?
q=mL (m=mass, L=heat of transformation, latent heat)
What is an isobaric process?
process in which pressure is constant.
What is an adiabatic process?
process in which heat is constant, change in internal energy U= -W
What is an isothermal process?
process in which temperature doesn’t change.
change in U=0, Q=W.
What is an isochoric process?
Process in which volume doesn’t change.
change in U=Q. U=Q because change in volume being zero makes work=0.
Second law of thermodynamics=?
objects in thermal contact and NOT in thermal equilibrium will exchange heat (high->low).
What is entropy?
the amount of dispersal (increase in available microstates) of energy at a specific temperature.
Equation for calculating total enthalpy of a reaction?
+/- H means…?
H(reaction = H(products) - H(reactants)
+H -> endothermic - reactions that break bonds (which requires energy)
-H -> exothermic - reactions that form bonds
cannot determine spontaneity from enthalpy!
What is the heat of formation for elements in their standard state?
zero (if in the correct standard phase)
Hess’s law
total enthalpy = sum of all steps (applies to all states functions)
What is the bond dissociation energy?
amount of energy required to break a bond (always endothermic)
