Thermodynamics Flashcards
Avogadro’s Law
under the same conditions of temperature and pressure, equal volumes of different gases contain an equal number of molecules
Charles’s Law
experimental gas law that describes how gases tend to expand when heated
Heat
Thermal motion
Temperature is a way to compare heat energy between objects
Statistical view of temperature
Average kinetic energy is proportional to temperature
- Maxwell Boltzmann curve
Boyle’s Law
The absolute pressure exerted by a given mass of an ideal gas is inversely proportional to the volume it occupies if the temperature and amount of gas remain unchanged within a closed system
Ideal Gas Law
PV = nRT R = 8.314 J/mol x K
Work as a form of energy
force x distance
Heat as a form of energy
- Macroscopic expression of the microscopic motion of atoms or molecules
- Heat.(q): random motion/energy
- Work (w): directed/organised motion/energy
Joule Experiment
- heat and work can be interconverted
- quantity of heat capable of increasing the temperature of one pound of water by 1 degree Farenheit requires the expenditure of a mechanical force (fall of 772 lbsby one foot)
Isolated System
No exchange of matter or energy
Closed System
Exchange of energy but not matter
Open System
Exchange of both matter and energy
Enthalpy
- practical expression of the first law of thermodynamics
H = U + (PV) - changes in enthalpy means heat has moved in/out of the system
- enthalpy can be thermal energy or a phase transition
Heat capacity
The amount of heat to be supplied to a given mass of a material to produce a unit change in its temperature.
= q/T
Chemical forms of Enthalpy
Energy storage in a molecular system
- covalent bonds
- weak bonds
- bond energy is a form of enthalpy without decreasing volume
- enthalpy is molecular motion and organisation
Boltzman Constant
Kb = R / na
Statistical View of Entropy
- no work done or enthalpy changes
- entropy (S) = Kb x ln Q
Q = number of microstates corresponding to a particular macrostate - probability equation relating the entropy of the gas to the number of real microstates corresponding to the gas’s macrostate
- shows the relationship between entropy and the possible number of ways the atoms/molecules can be arranged
Thermodynamic view of entropy
S = nR ln (V2/V1)
S = q/T
Entropy of universe = entropy of system + entropy of surroundings
Based on the second law of thermodynamics
Gibb’s Free Energy
G = H - TS
Enthalpy Driven and Entropy Driven Reactions
- reactions can be favorable entropically and enthalpically (exergonic)
- sometimes one factor drives the spontaneity of the reaction
Ligand Binding
Favorable: - forming protein ligand bonds - re organisation of water Unfavorable: - loss of ligand mobility - breaking protein water and ligand water bonds and water water bonds
Overall, there is a decrease in entropy but a larger increase in enthalpy so the reaction is spontaneous and enthalpy driven
Protein Folding
Favorable:
- internal H bond formation in protein
- internal van der Waals bonds in protein
- re organisation of water (hydrophobic effect)
Unfavorable:
- breaking protein water and water water bonds
- loss of conformational flexibility
Chemical Potential
- energy change during a chemical reaction or phase transition
- dependent on both the intrinsic chemical energy of the system (chemical bonding) and the concentration of the molecule
- difference in this is the potential energy difference to establish a diffusional equilibrium
Free energy and equilibrium
G = -RT ln Keq
The standard free energy change of a reaction tells us the Keq when allowed to come to equilibrium
Energy Coupling
- Unfavorable reaction can be coupled to a favorable one to drive it spontaneously
eg. ATP coupling to biological reactions
Steady State Conditions
- concentrations of reactants and products may be constant but not at equilbrium
- this is often seen in cells
- G = Go + RT ln [products]/[reactants]
Electrochemical Reactions
G = -nFE E = electric potential (volts) \+ = favorable - = non favorable
Half reactions
- redox reactions (either reduction or oxidation) with associated voltages
- adding them together gives overall voltage and spontaneity
Van’t Hoff Plot
Relates the change in Keq (ln Keq) to the Temperature (1/T)
y Intercept: S/R
slope: H/R
Membrane Potential
Y = membrane potential G = concentration and electrical potentials -96 mV G = RT ln (in/out) + z x F x Y Negative inside and positive outside
Nernst Equation
Y = -RT/zF x ln [in]/[out]
Active Transport
ATP use to move ions out of the cell
Find G of ion movement and couple this to ATP hydrolysis (-52.7 kJ/mol)
