AMALIA SHOLEHAHJURUSAN TEKNIK METALURGI

FT – UNTIRTA

THERMODYNAMICS

Overview

General Chemistry Physical Chemistry

First Law:The internal energy of an isolated system is constant

Zeroth Law:If two thermodynamics systems are in thermal equilibrium with a third, they are also in thermal equilibrium with each other

First Law:The energy of an isolated system is constant. It implies that energy can never be created or destroyed, it can only change its form. For a system U = q + w ; Where (U) represents a change in internal energy, (q) is the change in thermal energy and (w) is the work done

Second Law:A spontaneous change is accompanied by an increase in the total entropy of the system and its surroundings

Second Law:Whenever a spontaneous event takes place it is accompanied by an increase in the entropy of the universe

Third Law:For a pure crystalline substance, S = 0 at 0°K

Study of the patterns of energy change" thermo" energy

"dynamics" the patterns of changeDeals mainly with

(A) energy conversion (B) the stability of molecules (C) direction of change

Laws of Thermodynamics

They control interactions of everything in the universe - regardless of scale

Classical physics is, from a certain perspective, entirely based on Newton's Laws of motion only applicable in certain conditions

Development of the Laws of Thermodynamics actually began thousands of years ago

The largest advancements in developing the Laws of Thermodynamics occurred in the mid-1800s Joule’s experiment First Law of Thermodynamics

Not long after Clausius theory Second Law of Thermodynamics

Around 1906 Nernst theory Third Law of Thermodynamics

State of a System

System physical universe that is under consideration

System is separated from rest of universe by Real / Imaginary boundary

Surroundings part of universe outside the boundary

Thermodynamics Properties

Extensive properties Depend on the size of the system Ex : Volume (V), mass

Intensive properties Not depend on the size of the ystem Ex : Pressure (P), Temperature (T), density

Thermodynamics Process

P – V conjugate pair transfer of mechanical or dynamic energy as the result of work Isobaric process occurs on constant pressure

(dynamically connected) Isochoric / isometric process occurs on constant

volume (dynamically insulated)

T – S conjugate pair transfer of thermal energy as the result of heating Isothermal process occurs on constant temperature

(thermally connected) Isentropic process occurs on constant entropy Adiabatic process no energy added or subtracted

from the system by heating or cooling (thermally insulated)

State Variables (Thermodynamic Coordinates)

When a system is at equilibrium its state defined entirely by the state variable not depend on history of system

Ex : pressure (P), temperature (T), internal energy (U), enthalpy (H), enthropy (S), and Gibbs energy (G)

Zeroth Law

“ If two thermodynamics systems are in thermal equilibrium with a third, they are also in

thermal equilibrium with each other ”

A B

C

A system in thermal equilibrium is a system whose macroscopic properties (like pressure, temperature, volume, etc.) are not changing in time

When two systems are in thermal equilibrium: both of the systems are in a state of equilibrium, they remain so when they are brought into

contact, where 'contact' is meant to imply the possibility of exchanging heat, but not work or particles

If a fluid is in thermal equilibrium with another system: it has only one independent variable the macroscopic properties have certain values

Isotherm Plot

Boyle’s Law PV = f(θ)

Gay-Lussac’s Law (PV)1

(PV)2

= (1, 2)

(PV)1

(PV)2

=T1

T2

= (PV)2

T2

(PV)1

T1

Ideal gas

R = ideal gas constant

(PV)T

= nR