Sunday, February 3, 2008

JEE Revision - Chemical Energetics - Introduction

Thermodynamics is the study of energy and energy changes.

Energy is the capacity to do work.

Energy is present in variou forms like, potential energy, kinetic energy, electrical etc.

Energy and energy changes are measured in terms of heat energy.

The study of the flow of heat or any other form of energy into or out of a system as it undergoes a physical aor chemical transformation is called thermodynamics.

The branch of thermodynamics dealing with energy changes accompanying chemical transformation is called chemical thermodynamics.



Open system: A system which can exchange matter as well as energy with the surroundings is called an open system.

Closed system: A system which can exchange energy but not matter with the surroundings is called a closed system.

Isolated system: A system which can neither exchange matter nor energy with the surroundings is called an isolated system.


Isothermal: Temperature of the system is constant.

Adiabatic: No heat flows into or out of the system.

Isochoric: volume of the system remains the same.

Isobaric: Pressure of the sytem remains the same.

Reversible: The system changes in infinitesimal steps and they can be reversed.

Irrevesible: Real life systems do not satisfy the reverbility criterion and hence irreversible.

Modes of transfer of energy between system and surroundings

1. Heat (Q): Energy is exchanged between the system and the surroundings as heat if they are at different temperatures.

2. Another modes of transfer of energy is work. Work is said to be performed if th point of application of a force is displaced in the direction of the force.

Pressure volume work

Pressure volume work is mechanical work. It is the work done when the gas expands or contracts against external pressure.

It is equal to force multiplied by distance moved or pressured mulitiplied by change in volume.

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