DIGITAL TEXT
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Diffusion
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INDEX
SL. NO.
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CONTENTS
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PAGE NO.
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1.
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INTRODUCTION
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4
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2.
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DEFINITION OF DIFFUSION
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5
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3.
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DESCRIPTION ABOUT DIFFUSION
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6-7
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4.
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APPLICATION
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8
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5.
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WORKED OUT EXERCISE
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9
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6
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APPENDIX
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10
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7
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REFERENCE
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11
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PREFACE
I develop a simple pack of information’s on Diffusion by the assistance of two videos. It is very useful to the high school students for studying this topic. This file can open anyone without any restrictions. The video representation can be used and lay let a path for future work that requires a more flexible version.
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INTRODUCTION
The contemporary literature on any topic on Chemistry subject is not enough to teach the students. They need well proof and also hands own experience. Here introducing two videos related diffusion. The video is simple and attractive, so the students can easily understand the concept of diffusion.
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DIFFUSION
Molecular diffusion, often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero.
ANOTHER DEFINITION
Diffusion is the spontaneous mixing of one substance with another when in contact or separated by a permeable membrane. Diffusion is a result of the random motions of their component atoms, molecules, ions or other particles.
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The movement of particles from a higher concentration to a lower concentration is called diffusion. The ratio of this movement is a function of temperature, viscosity of the fluid and the size (mass) of the particles. Once the concentrations are equal to the molecules continue to move, but since there is no concentration gradient the process of molecular diffusion has ceased and is instead governed by the process of self-diffusion, originating from the random motion of the molecules. The result of diffusion is a gradual mixing of materials such that the distribution of molecules is uniform.
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VIDEO-1
The mixing of molecules itself having molecular motion is called diffusion. Fundamentally, two types of diffusion are distinguished. Tracer diffusion and self-diffusion.
Tracer diffusion and self-diffusion, which is a spontaneous mixing of molecules taking place in the absence of concentration (or chemical potential) gradient. This type of diffusion can be followed using isotropic tracers, hence the name. The tracer diffusion is usually assumed to be identical to self-diffusion.
Chemical diffusion occurs in a presence of concentration (or chemical potential) gradient and it results in net transport of mass. This is the process described by the diffusion equation. Chemical diffusion increases the entropy of a system. ie; diffusion is a spontaneous and irreversible process.
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APPLICATIONS
Diffusion is of fundamental importance in many disciplines of physics, chemistry and biology. Some example applications of diffusion:
i. Sintering to produce solid materials (powder metallurgy, production of ceramics
ii. Chemical reactor design
iii. Catalyst design in chemical industry
iv. Steel can be diffused (eg: with carbon or nitrogen) to modify its properties.
v. Doping during production of semiconductors.
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WORKED OUT EXERCISE
The smell of flowers are spread over the area, why?
The reason behind the spreading of smell of flower is diffusion. That is the molecules in the flowers are moving from high concentration to low concentration.
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PRACTICE QUESTIONS
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APPENDIX
Diffusion:
When particles move to a lower area of concentration from a high area of concentration.
Concentration:
The amount of a substance dissolved in a liquid.
Spontaneous:
Something that happens all by itself, without any outside stimuli.
Molecule:
The smallest particle of an element or component capable of a stable, independent existence.
Particle:
Small portion of matter.
Entropy:
The thermodynamic quantity measuring the disorder of a substance
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REFERENCES
Ø New edition 8th standard text book
Ø www.wikipedia.com
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