Thermodynamics Flashcards
Define heat.
Transfer of thermal energy from a hotter object to a colder object
What is 0˚ C in Kelvin?
273K
Conversion of F –> C
(9/5)C + 32
When solids or liquids experience a change in temperature, their length or volume changes. What are the corresponding formulas to determine this change?
For ∆L (applicable to solids only):
∆L = αL∆T
For ∆V (solids & liquids):
∆V = βV∆T
**α and β are constant values
State functions
Functions that describe the equilibrium state of a system, independent of the path taken by the system to arrive to its present state
Pressure, volume, temperature, entropy
Process/path functions
Functions that describe the path taken by a system to transition from 1 equilibrium state to another
Work, heat
Equation to calculate total internal energy of a system:
∆U = Q - W
If W is negative, work is being done (on/by) the system.
If W is positive, work is being done (on/by) the system.
-W = work is done on the system
+W = work is done by the system
3 methods of heat transfer:
Conduction, convection, radiation
Conduction
direct transfer of energy through physical contact/molecular collisions
Convection
transfer of heat by the physical motion of a liquid or gas over a material
*SOLIDS don’t participate in convection
Radiation
transfer of energy by electromagnetic waves ;can transfer energy through a vacuum
Ex: Sun warming the Earth
During a phase change, temperature is (changing/constant), even though heat is added or removed.
Constant
SI unit of heat
Joules (J)
Specific heat of water
1 cal/g˚C or 4.184 J/g*K or 420 J/˚C
0th Law of Thermodynamics
Objects that are in thermal contact & not in thermal equilibrium, will exchange heat traveling from the hotter object to the cooler object
1st Law of Thermodynamics
Energy can be transferred, but it isn’t created or destroyed.
2nd Law of Thermodynamics
Entropy of an isolated system always increases; heat will flow from a hotter object to a colder object
Calculating heat energy (q)
q = mC∆T
c is the specific heat capacity
Difference between specific heat capacity and heat capacity
Specific heat capacity - amt. of heat required to raise the temp of 1 g of substance by 1˚C
Heat capacity - amt. of heat required to raise temp of entire sample by 1˚C
Another version of calculating heat:
q = C∆T
no mass required
*If given a problem where one material loses heat & other gains heat, set q’s equal to each other
Change in entropy equation
∆S = Qrev/T
Qrev is the heat gained or lost in a reversible process
T is measured in Kelvin
True or false:
In order to concentrate or confine energy, it requires work.
Yes, because energy spontaneously disperses, so in order for it to be confined some amount of work should be used to confine it to one area.
Calorimeters are an example of what type of system: isolated, closed or open?
Isolated systems because neither energy nor matter is exchanged.