87773961 Thermodynamics Basics (1)

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

ThermodynamicsThermodynamicsBasic principles

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

What is thermodynamics?What is thermodynamics?

The science of reciprocal transfer of energy within a The science of reciprocal transfer of energy within a system and between different systemssystem and between different systems

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Questions, discussion:Questions, discussion:

Describe the energy flow and transformations necessary for a grain of wheat to become a slice a bread

The greenhouse effect:

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UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Thermodynamic systemsThermodynamic systems

Thermodynamic system = Thermodynamic system = macroscopic systemmacroscopic system, , composed of a large (but finite!) number of particles, which composed of a large (but finite!) number of particles, which interact energeticallyinteract energetically among them and with the exterior among them and with the exterior environmentenvironment

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Which one is a thermodynamic system?Which one is a thermodynamic system?

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Measurable physical amounts, that define the stateMeasurable physical amounts, that define the state

TemperatureTemperature PressurePressure

Number of molsNumber of mols MassMass VolumeVolume

Intensive parameters:Intensive parameters:➔ Not influenced by the size of the Not influenced by the size of the

systemsystem

Extensive parameters:Extensive parameters:➔ Depend on the size of the systemDepend on the size of the system

State of a system – state parametersState of a system – state parameters

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

State parametersState parameters

TemperatureTemperature – a measure of the thermal motion – a measure of the thermal motion

PressurePressure – reflects the force of the molecules hitting the – reflects the force of the molecules hitting the container's walls, divided by the surface of the wallscontainer's walls, divided by the surface of the walls

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UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Legea universala a gazelor:Legea universala a gazelor:

pV = pV = RTRT

p – presiunea gazuluip – presiunea gazului V – volumul ocupatV – volumul ocupat - numarul de moli- numarul de moli R – constanta universala a gazelor R – constanta universala a gazelor

(R = 8.314 J/kmol ∙K)(R = 8.314 J/kmol ∙K) T - temperaturaT - temperatura

Ideal gas law:Ideal gas law:

pV = pV = RTRT

p – pressurep – pressure V – volumeV – volume - number of mols- number of mols R – universal gas constantR – universal gas constant

(R = 8.314 J/kmol ∙K)(R = 8.314 J/kmol ∙K) T - temperatureT - temperature

Connection between p, V and TConnection between p, V and T

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Questions, discussionQuestions, discussion

Explain, for an isolated thermodynamic system, considering the molecular explanations for temperature and pressure:

What happens to the pressure of a gas, maintained at constant volume, when temperature increases

What happens to the volume of a gas, maintained at constant pressure, if the temperature increases

What happens to the pressure of a gas, maintained at constant temperature, if the volume increases

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Thermodynamic processThermodynamic process

Evolution of a thermodynamic system from one state Evolution of a thermodynamic system from one state to anotherto another

ReversibleReversible processes: processes: Cvasistatic (at any moment in time, the system is at equilibrium)Cvasistatic (at any moment in time, the system is at equilibrium) If the sense of variation for the thermodynamic parameters is If the sense of variation for the thermodynamic parameters is

reversed, the system returns to the initial state following the same reversed, the system returns to the initial state following the same pathway (it goes through the same states, only in reversed order)pathway (it goes through the same states, only in reversed order)

IrreversibleIrreversible processes processes Non-cvasistaticNon-cvasistatic If possible, the return to the initial state is on a different pathway and If possible, the return to the initial state is on a different pathway and

requires external interferencerequires external interference

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

http://members.fortunecity.com/rickteuscher/index.html

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Questions, discussionQuestions, discussion

After a few hours of driving, the temperature inside the tires of a cars increases from 17°C to 27°C. What's the relative increase in pressure?

When will the volume of a gas inside an isolated elastic balloon (p = ct) increase more (no gas escapes the container) ?:

When 10 l of hydrogen are heated with 10°C When 10 l of carbon dioxide are heated with 10°C

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Thermodynamic equilibriumThermodynamic equilibrium

State parameters areState parameters are constant spatially constant spatially, within the , within the system, and system, and don't change over timedon't change over time

The spontaneous evolution of a thermodynamic system is The spontaneous evolution of a thermodynamic system is towards equilibriumtowards equilibrium

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

The principles of thermodynamicsThe principles of thermodynamics

Principle 0 Transitivity of thermal equilibrium (if object A is in thermal equilibrium

with object B, and B is in thermal equilibrium with C, then A and C are in thermal equilibrium)

Principle I Conservation of internal energy

Principle II Entropy; spontaneous direction of evolution for thermodynamic

systems

(Principle III) The entropy of a system approaches 0 when the temperature

approaches 0 K.

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

❒ Internal energy of a systemInternal energy of a system – extensive state parameter

➔ total energytotal energy of a system of a system

KineticKinetic energy: energy: TranslationalTranslational RotationalRotational Vibrational Vibrational

PotentialPotential energy energy Attraction between moleculesAttraction between molecules Interaction with external fields Interaction with external fields

(electric etc)(electric etc) Intramolecular, intraatomic Intramolecular, intraatomic

energiesenergies

The variation of internal energy of a system depends on the initial state and the final state, but not on the pathway of evolution between states

The IThe Ithth principle of thermodynamics principle of thermodynamics

time

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Energia interna a unui sistem (U) creste cand sistemul primeste Energia interna a unui sistem (U) creste cand sistemul primeste caldura (Q) din exterior si scade cand sistemul efectueaza lucru caldura (Q) din exterior si scade cand sistemul efectueaza lucru mecanic (L)mecanic (L)

CalduraCaldura – – transfer de energie datorat miscarii dezordonate a transfer de energie datorat miscarii dezordonate a moleculelormoleculelor (Q > 0 cand sistemul primeste caldura)(Q > 0 cand sistemul primeste caldura)

Lucrul mecanicLucrul mecanic – – transfer de energie datorat miscarii ordonate transfer de energie datorat miscarii ordonate a sistemului a sistemului (L > 0 cand sistemul efectueaza lucru mecanic)(L > 0 cand sistemul efectueaza lucru mecanic)

U=Q−L

The internal energy of a system (U) increases when the system The internal energy of a system (U) increases when the system receives heat from the exterior (Q) and decreases when the receives heat from the exterior (Q) and decreases when the system does work (L)system does work (L)

HeatHeat – – energy transfer due to chaotic movement of molecules energy transfer due to chaotic movement of molecules (Q > 0 when the system receives heat)(Q > 0 when the system receives heat)

WorkWork – – energy transfer due to ordered movement of the system energy transfer due to ordered movement of the system (L > 0 when system does work)(L > 0 when system does work)

Mathematical expression of the IMathematical expression of the Ithth principle of thermodynamicsprinciple of thermodynamics

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

IIthth law of thermodynamics law of thermodynamics = ENERGY CONSERVATION LAW = ENERGY CONSERVATION LAW

The energy is never lost, it changes from one form to anotherThe energy is never lost, it changes from one form to another

IsolatedIsolated system – system – conservation of internal energyconservation of internal energy

((U = 0)U = 0)

Impossibility of construction of a Impossibility of construction of a perpetuum mobile:perpetuum mobile:

No machine can be build to produce work without energy No machine can be build to produce work without energy inputinput

Conservation of energyConservation of energy

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

State parameterState parameter

Expresses the disorder in a thermodynamic systemExpresses the disorder in a thermodynamic system

S=QT

● Q – heat exchanged by the system with the exteriorQ – heat exchanged by the system with the exterior● T – temperatureT – temperature

IIIIndnd law of thermodynamics - Entropy law of thermodynamics - Entropy

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

● Q – caldura schimbata de sistem cu exteriorulQ – caldura schimbata de sistem cu exteriorul● T – temperatura la care are loc schimbul de caldurT – temperatura la care are loc schimbul de caldura

IIIIndnd law of thermodynamics - Entropy law of thermodynamics - Entropy

Boltzmann definitionBoltzmann definition Entropy expresses the order among the particles from which the Entropy expresses the order among the particles from which the

system is madesystem is made

S=k ln N

k – Boltzmann's constant (1.38 k – Boltzmann's constant (1.38 ·· 10 10-23-23 J/K) J/K) N – thermodynamic probability of a stateN – thermodynamic probability of a state

➔ Number of distinct microscopic states Number of distinct microscopic states corresponding to a macroscopic statecorresponding to a macroscopic state

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

IIIIndnd law of thermodynamics - Entropy law of thermodynamics - Entropy

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Spontaneous evolution of thermodynamic Spontaneous evolution of thermodynamic systemssystems

All spontaneous processes occurring in an isolated thermodynamic system lead to:

Increased Increased entropyentropy

Decreased free Decreased free energy energy (part of the (part of the internal energy of a internal energy of a system that can be system that can be transformed into work)transformed into work)

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Author: David van der Spoel, Uppsala University (Sweden), [email protected]

Title: Picosecond Melting of Ice by an Infrared Laser Pulse: A Simulation Study

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Questions, discussionQuestions, discussion

How is the entropy changing in the following examples of thermodynamic processes:➔ Protein synthesis➔ Aging of a biological organism➔ Digestion of nutrients➔ Water heating

What happens to the entropy of an isolated system?

What happens to the entropy in a reversible process?

UMF Carol Davila – Dept. of Biophysics Thermodynamics (basics) (AP)

Supplementary readingsSupplementary readings

http://web.mit.edu/16.unified/www/FALL/thermodynamics/

http://www.slideshare.net/ercolino/introductory-biological-thermodynamics

http://llk.media.mit.edu/projects/emergence/index.html