Module 3 Flashcards
What does kinetics tell you/measure?
How fast, temperature
What does thermodynamics measure/tell you?
How much
Definition of internal energy
The energy that’s intrinsic to a material
State functions
Tells us the state of the system.
Does NOT depend (mathematically) on how we got from A to B, just uses the initial and final conditions.
Value is dependent only on the state the system is in, never on how that state was reached.
Path functions
(Mathematically) depends on how we got from A to B. Measures what happens in between the initial and final conditions.
Value is dependent on how the state of the system was reached.
First Law of Thermodynamics
The energy of the universe is constant.
The total change in energy of a system consists of the heat transferred to (delta H or q) and the work done (w) on a system.
If something releases heat, it is…
Exothermic
If something absorbs heat, it is…
Endothermic
Definition of specific heat capacity
The quantity of heat required to increase the temperature of one gram of a substance by one degree C/K
Is delta H (change in enthalpy) a state function or a path function?
State function. It uses only the initial and final conditions.
What does calorimetry measure?
Heat flow
Is enthalpy (H) a state function or a path function?
It’s a state function.
Note that enthalpy values can’t be measured directly. Only changes in enthalpy can be determined.
If delta H is negative…
…the rxn is exothermic, indicates that heat has been lost from the system.
If delta H is positive…
…the rxn is endothermic, indicates that heat has been gained in the system.
What does delta H predict?
Whether reactions will be endothermic or exothermic.
What does entropy predict?
Whether reactions will be spontaneous or not.`
Second Law of Thermodynamics
The entropy of the universe is increasing to a maximum.
What happens to entropy if the temperature of the system increases while volume remains constant?
Entropy increases, delta S is positive
What happens to entropy if the volume of the system increases while temperature remains constant?
Entropy increases, delta S is positive
What happens to entropy if both the temperature and the volume of a system increase?
Entropy increases, delta S is positive
What three properties do liquids have?
Viscosity (resistance to flow)
Surface tension
Vapor pressure
What would make a liquid more viscous?
Decreasing the temperature, decreasing the IMFs present
What would increase a liquid’s surface tension?
Strengthening the IMFs
What would increase a liquid’s vapor pressure?
Weakening the IMFs, increasing temperature
When at low temperatures is a rxn spontaneous?
At low temps, delta G is roughly equal to delta H.
Rxn must be endothermic (delta H is negative) for it to be spontaneous.
When at high temperatures is a rxn spontaneous?
At high temps, delta G is roughly equal to -TdeltaS.
Rxn must increase in entropy (delta S is positive) for it to be spontaneous.
How does delta G predict spontenaity?
When delta G is negative, rxn is spontaneous.
When delta G is positive, rxn is NOT spontaneous, instead the reverse rxn is spontaneous.
When delta G = 0, the system is at equilibrium and neither the forwards nor reverse rxns are spontaneous.