THERMOCHEMISTRY

Prepared by: Nor Fatihah binti NawiMatrix no: A132797Programme: sarjanamuda pendidikan dengan kepujian (mathematics)

CHAPTER OUTLINE

18.1 INTRODUCTION TO THERMODYNAMICS

18.2 SPONTANEOUS PROCESSES

18.3 ENTROPY (S)

18.4 THE SECOND LAW OF THERMODYNAMICS

18.4 THE THIRD LAW OF THERMODYNAMICS

FURTHER INFORMATION

6.1 INTRODUCTION TO THERMODYNAMICS

The First Law of Thermodynamics Based on the law of conservation of energy ,

states that energy can be converted from one to another but cannot be created or destroyed.

Therefore the total energy of the universe is a constant.

Test the validity of first law by measuring the change in the internal energy.

E = Ef – Ei

E: energy change Ef: final energy Ei: initial energy

6.1 INTRODUCTION TO THERMODYNAMICS

The Second Law of Thermodynamics Explain why chemical processes tend to

favor one direction

The Third Law of Thermodynamics An extension of the second law

18.2 SPONTENUOS PROCESSES

A reaction that does occur under the given set of condition

The processes occur spontaneously in one direction cannot under the same condition.

Examples of physical and chemical processes in every day: A waterfall runs downhill but never up

spontaneously Heat flows from a hotter object to a colder one, but the reverse never happens spontaneously. Iron exposed to water and oxygen forms rust, but rust does not spontaneously change back to

iron.

18.2 SPONTENUOS PROCESSES

18.3 ENTROPY (S)

A measure of how spread out or dispersed the energy of a system is among the different possible ways that system can contain energy.

Entropy can be thought of as a measure of the randomness of a system.

It is related to the various modes of motion in molecules.

Therefore, S = Sfinal Sinitial

18.3 ENTROPY (S)

For a process occurring at constant temperature (an isothermal process):

qrev = the heat that is transferred when the process is carried out reversibly at a constant temperature.T = temperature in Kelvin.

18.3 ENTROPY (S)

STANDARD ENTROPY Entropy is obtained by calorimetric method. These are molar entropy values of substances in their standard states. Standard entropies tend to increase with increasing molar mass.

18.3 ENTROPY (S)

CHANGES IN ENTROPY A system with fewer microstates(smaller

W) among which to spread its energy(small dispersal) has a lower entropy.

A system with more microstates (large W) among which to spread its energy (large dispersal) has a higher entropy.

18.4 THE SECOND LAW OF THERMODYNAMICS

The entropy of the universe increases in a spontaneous process and remains unchanged in an equilibrium process.

Spontaneous process:

Equilibrium process:

18.4 THE THIRD LAW OF THERMODYNAMICS

The entropy of a perfect crystallines subtances is zero at the absolute zero of temperature.

18.4 THE THIRD LAW OF THERMODYNAMICS

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FURTHER INFORMATION

You can get more information on this topic by other power point presentation as below:

http://search.sweetim.com/search.asp?src=6&q=thermodynamic+powerpoint+presentation

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