Phase Changes and Thermodynamics Flashcards
Is the change in enthalpy positive or negative for vaporization?
positive enthalpy change
Define melting
solid to liquid
Is the change in entropy positive or negative for vaporization?
positive entropy change
The balance between enthalpy and entropy is controlled by?
temperature
At any given temperature the most stable phase is the substance with?
the lowest free energy
What phase are most substances in at high temps?
gases
Is the change in enthalpy positive or negative for condensation?
negative enthalpy change
Is the change in entropy positive or negative for condensation?
negative entropy change
What does the entropy tell us?
The entropy tells us about the number of potential microstates for distributing energy
• The higher the entropy, the more likely such a state is to randomly occur
Describe the relationship between entropy and phases
• Solids are low in entropy and gases are high in entropy
What is the Gibbs Free Energy Formula?
G = H - TS
Is the change in entropy positive or negative for sublimation?
positive entropy change
Describe the relationship between enthalpy and molecular distance
The enthalpy of two molecules in close proximity is lower than two molecules separated by some distance
What always leads to a lower overall free energy?
spontaneous chanes
Define sublimation
solid to gas
Describe the relationship between entropy and number of molecules
Entropy increases with increasing the number of molecules
At high temps does enthalpy or entropy dominate?
entropy
Define vaporization
liquid to gas
Describe the relationship between entropy and temperature
Entropy increases with increasing temperature
What is it mean when G = 0?
the system has reached equilibrium
Is the change in entropy positive or negative for deposition?
negative entropy change
Is the change in entropy positive or negative for melting?
positive entropy change
Define freezing
liquid to solid
What phase are most substances in at low temps?
solids
Is the change in enthalpy positive or negative for melting?
positive enthalpy change
Describe the relationship between enthalpy and phases
The lowest enthalpy phase is the solid phase and the highest is the gas phase
Is the change in entropy positive or negative for freezing?
negative entropy change
Describe the relationship between entropy and volume
Entropy increases with increasing volume
Does the universe tend toward higher or lower entropy?
higher
Define deposition
gas to solid
Define condensation
gas to liquid
Does the universe tend toward higher or lower enthalpy?
lower
At low temps does enthalpy or entropy dominate?
enthalpy
Is the change in enthalpy positive or negative for freezing?
negative enthalpy change
Is the change in enthalpy positive or negative for deposition?
negative enthalpy change
Is the change in enthalpy positive or negative for sublimation?
positive enthalpy change
