LESSON 1: Thermodynamics of Biosystems

Thermodynamics

deals with the transfer of energy from one place to another and from one form to another

Zeroth Law

when two systems are each in thermal equilibrium with a third system, the first two systems are in thermal equilibrium with each other

First Law of Thermodynamics

the change in a system’s internal energy is equal to the difference between heat added to the system from its surroundings and work done by the system on its surroundings

∆U = Q - W

Formula for the First Law of Thermodynamics

Pressure

force per unit area

Work

when an object moves on the effect of force

Isothermal Process

is any process in which the temperature of the system remains constant

Isochoric Process

is one in which the volume is held constant, meaning that the work done by the system will be zero

Adiabatic Process

is where a system exchanged no heat with its surroundings

Second Law of Thermodynamics

heat does not flow spontaneously from a colder region to a hotter region, or, equivalently, heat at a given temperature cannot be converted entirely into work

Arrow of Time

is the one-way direction or asymmetry of time, moving strictly from the past to the future, which is driven by the second law of thermodynamics

Third Law of Thermodynamics

the entropy of a perfect crystal of an element in its most stable form tends to zero as the temperature approaches absolute zero ; becomes perfectly ordered

Boltzmann Formula

shows the relationship between entropy and the number of ways the atoms or molecules of a thermodynamic system can be arranged

Entropy

a measurement of the degree of randomness of energy in a system ; the lower the entropy the more ordered and less random it is, and vice versa

System

is simply a collection of objects within some boundary

Open System

is a system that freely exchanges energy and matter with its surroundings

Closed System

is a system that exchanges only energy with its surroundings, not matter

Isolated System

does not exchange energy or matter with its surroundings

Temperature

is a physical quantity expressing hot and cold ; it is measured with a thermometer calibrated in one or more temperature scales

Energy

has a precise meaning in physics that does not always correspond to everyday language, and yet a precise definition is somewhat elusive ; cannot be created nor destroyed

Ergon

work

Joule

SI unit for energy and work ; 1 Joule is equal to 1 Newton Meter

W = FL

Formula for Work

Calorie

is an energy measurement unit ; is a pre-SI measurement unit of energy or heat

Energy

conserved quality

Law of Conservation of Energy

energy can be converted in form, but not created or destroyed

Potential Energy

stored energy that depends upon the relative position of various parts of a system

Kinetic Energy

form of energy that an object or particle has by reason of its motion

KE = ½ mv²

Formula for Kinetic Energy

Gravitational Potential Energy

is the energy stored in an object due to its position above the Earth’s surface

E_P = mgh

Formula for Gravitational Potential Energy

Thermal Energy

is energy possessed by an object or system due to the movement of particles within the object or the system

Thermodynamic Potentials

are useful in the chemical thermodynamics of reactions and non-cyclic processes

Internal Energy U

is defined as the energy associated with the random, disordered motion of molecules

U

is the most common symbol used for internal energy

∆U = Q + W

Formula for Internal Energy U

Enthalpy H

it is a useful quantity for tracking chemical reactions

∆H = U + PV

Formula for Enthalpy H

Helmholtz Free Energy F

helps determine how much energy is able to be used by available energy to do work ; donated by F

F = U - TS

Formula for Helmholtz Free Energy F

TS

Energy you can get from the system’s environment by heating

F

maximum amount of work a system is able to perform during a thermodynamic process with constant T

Q = ST

represents heat obtained from the environment

Gibbs Free Energy G

helps identify spontaneous reaction ; always negative ; maximum amount of work obtainable from a reaction

G = U - TS + PV

Formula for Gibbs Free Energy G

Reversible

if the process can return back in such that both the system and the surroundings return to their original states, with no other change anywhere else in the universe ; this doesn’t exist in this world

Irreversible

only this occurs in this universe, free energy is decreased and entropy is increased ; process that cannot return back ; everything is irreversible because you already used energy

Steady State

during this state, entropy is increased, heat is produced in the body and the same amount of heat is released from the organism so that body temperature stays constant at about 37 degrees Celsius

Hess’s Law of Constant Heat Summation

states that regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes