Chapter 3: Thermodynamics Flashcards
Temperature measures these parts of internal energy…
Rotational
Transitional
Vibrational
6 Internal Energies
- ) Vibrational Energy- atoms vibrations within a molecule; atoms in monatomic gas have NO vibrational energy
- ) Rotational Energy- molecular movement where spatial orientation of the body changes and center of mass remains fixed; Atoms in a monatomic gas have NO rotational energy
- ) Transitional energy- movement of center of mass of a molecule
- ) Electronic Energy- potential electrical energy created by attractions b/n electrons and their nuclei; below 5000K, all molecules are at lowest energy level and if no molecular run occurs, electronic energy remains ms constant
- ) Intermolecular potential energy- energy created by the intermolecular forces b/n molecular dipoles; gas at room temp & pressure, IPE makes small contribution to internal energy but at higher pressure contributions become more significant
- ) Rest Mass energy- energy predicted by e=mc^2
Seven state functions
Title. State function. Prefix
1 Internal Energy. U
2 Temperature. T
3 Pressure. P
4 Volume. V
5 Enthalpy. H
6 Entropy. S
7 Gibbs energy. G
Zeroth law of thermodynamics states…
That temperature exists
Internal energies (vibrational, transitional, and rotational) describe energies of ….
Sum of these energies is called
Relationship in Increase in thermal energy is
Molecular motion
Thermal energy
Increase in temperature
Molecules vibrate faster in a…
Molecules in a solid only…
Solid as temps increase
Vibrate
Define enthalpy
H=U+PV
Units for Enthalpy is joules (energy)
(U=internal energy)
Change in enthalpy
(Delta)H=(delta)U+P(delta)V
Catalysts do not affect…
Equilibrium and enthalpy change
Catalyst affect …
The rate
What’s Entropy
Natures tendency toward “disorder” or the concept of “probability”
Second Law Thermodynamics
Entropy of isolated system will never decrease
The sum of entropy is…
Change of entropy system + change in surroundings = change in universe > or = 0
Entropy of system can ___________ only if at the same time the surroundings __________ by > or = magnitude
Decrease
Increases
Entropy dictates what?
Direction of a reaction
Entropy increases with…
Number
Volume
Temperature
If a reaction INCREASES the NUMBER of gaseous molecules, then the reaction has (+) entropy
Units of entropy
J/K
Change in entropy process will be the SAME as change in entropy for a _______ process between same 2 states
Reversible
Entropy is an EXTENSIVELY property which means…
It INCREASES with amount of substance
Three types of equilibrium
Mechanical - when system is NOT accelerating
Material - in material when no net chemical reaction is occurring and there’s no matter transferring within the system
Thermal - when temp is the SAME throughout; can also be in thermal equilibrium with its surroundings, meaning that’s the SAME temp as its surroundings
Important MCAT Equation: Gibbs Free Energy (G)
(Delta)G=(delta)H-T(delta)S
Refer to system and NOT surrounding
(Delta)G=0 which means…
-(delta)G indicates _______ reaction
Equilibrium
Spontaneous
Examples of non-PV work
Contracting muscles
Transmitting nerves
Batteries
Gibbs free energy represents the maximum ….
Non-PV work available from a reaction
Gibbs function [(delta)G, (delta)S, (delta)H] refer to changes in the ….
Gibbs is a function of both…
System
Enthalpy and entropy
Reaction produces ____ change in enthalpy and a _____ change in entropy, the reaction can NEVER be the spontaneous.
Reaction produces a ____ change in enthalpy and a _____ change in entropy, it must be SPONTANEOUS.
If signs of both enthalpy and entropy are the same for a reaction, then the spontaneity of the reaction will depend on _______.
Positive; Negative
Negative; Positive (decreasing; increasing)
Temperature
Oth Law
1st Law
2nd Law
3rd Law
- Temp exists and is a state function (2 bodies with the same system are in equilibrium with the SAME system in thermal equilibrium
- Energy of an isolated system is conserved for any reaction
- Entropy of the universe INCREASES for any reaction
- Perfect crystal at 0 K is assigned an entropy value of 0. All other substances and temps have a (+) entropy value
Summary:
1) heat and work are the only two ways to change the energy of a _________.
2) heat and work result in the change in ______ energy of a system at REST.
3) Temperature is as _______ and Pressure is as _______.
4) Think of enthalpy as ______, or think of change in enthalpy at CONSTANT pressure as ______.
5) Think of ENTROPY as the __________.
6) Entropy _________ with _______, _________, and __________.
7) Gibbs energy change is as a _____ of maximum amount of energy available to do _______ work such as electrical work in a cell.
1) SYSTEM
2) INTERNAL
3) thermal/mole and thermal/vol
4) U+PV; heat
5) SPREADING of energy
6) INCREASES with temperature, volume, and numbers
7) NEGATIVE; nonPV work
