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Summary

Introduction

Various physical and chemical reactions occur at the interfaces or boundaries of two different phases like solid–liquid interface, solid–solid interface, solid–gas interface, liquid–gas interface, liquid–solid interface and liquid–liquid interface. These reactions have been of great interest to the chemists worldwide as they have important applications in industrial and domestic field.

All these changes occurring at the boundaries of different phases are studied under a branch of chemistry called surface chemistry. Surface chemistry not only deals with the reactions occurring at the interfaces but also studies the nature of surfaces and the reactions taking place at the surfaces. Adsorption and colloidal properties are some of the important effects that occur at the solid – liquid interfaces.

Adsorption

The surface of solid or liquid has a tendency to attract and retain molecules of other species (gas or liquids). This phenomenon of attracting and retaining molecules on the surface is termed as adsorption (latin word surbere; to suck up). The material on the surface of which adsorption occurs is termed as adsorbent and the substance adsorbed on the surface is called adsorbate. Now, the question of why adsorption occurs arises. Adsorption occurs because of the presence of unbalanced forces at the surface of liquids and solids. In a solid or liquid, the molecules present in the bulk are attracted equally from all sides and the net force experienced by the molecule in the bulk is zero. However, the molecule that lies near the surface (known as surface molecule) is being attracted only by the molecules below it because there are no molecules above it (Fig. 14.1). Hence, a net downward force is experienced by the surface molecule. Because of this downward force, the surface molecule tends to attract and retain other species (a gas or a dissolved substance). These species do not penetrate inside the molecule but remain on the surface. Hence, their concentration is higher on the surface than in the bulk.

Common examples of adsorption are

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Contents

Chapter Thirteen - Multi-modal Imaging

Chapter Five - Designing a Hemodynamic Imaging Experiment

Introduction

Frontmatter

Chapter Seven - Basic Statistical Analyses

14 - Surface Chemistry

Summary

10 - Atomic Structure and Chemical Bonding

Index

Introduction

Part IV - Complementary Methods

5 - The Metaphysics of Logic

25 - Analytical Techniques in Chemistry

1 - Fuels

Index of Latin Words

6 - Polymers

2 - Water

Chapter Fourteen - Causal Methods to Modulate Brain Activity

Chapter One - Introduction and Overview

Part III - Electrophysiological Neuroimaging

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Summary