A unified overview of the dynamical properties of water and its unique and diverse role in biological and chemical processes.

Liquid-crystalline phases are now known to be formed by an ever growing range of quite diverse materials, these include those of low molecular weight as well as the novel liquid-crystalline polymers, such phases can also be induced by the addition of a solvent to amphiphilic systems leading to lyotropic liquid crystals. Irrespective of the structure of the constituent molecules these numerous liquid-cl)'Stailine phases are characterised by their long range orientational order. In addition certain phases exhibit elements of long range positional order. Our understanding, both experimental and theoretical, at the molecular level of the static behaviour of these fascinating and important materials is now well advanced. In contrast the influence of the long range order; both orientational and positional, on the molecular dynamics in liquid Cl)'Stais is less well understood. In an attempt to address this situation a NATO Advanced Study Institute devoted to liquid ctystal dynamics was held at n Ciocco, Barga, Italy in September 1989. This brought together experimentalists and theoreticians concerned with the various dynamical processes occurring in all liquid crystals. The skills of the participants was impressively wide ranging; they spanned the experimental techniques used in the study of molecular dynamics, the nature of the systems investigated and the theoretical models employed to understand the results. While much was learnt it was also recognised that much more needed to be done in order to advance our understanding of molecular dynamics in liquid Cl)'Stais.

When, in my capacity as President of the Societe de Chimie physique, I opened the 24th Annual Meeting of this Society, devoted this year to 'molecular motions in liquids', I was stirred by a particular emotion. This had two reasons, one general and the other rather personal. I would like to give an explanation in the Foreword to this volume of communications to the Meeting and their ensuing discussions. An essential characteristic of science is its international nature. It is like a symphony composed of contributions by all the countries playing together as an orchestra in unison. Just as a melody has different 'colours' when played by strings or woodwinds, so there exist similar 'colour' differences, subtle ones, between scientific contributions from different countries, rooted as they are in their own cultural history and liable to impoverish the ensemble if they should cease to participate. I have always had an impression of marked 'colour' differences prevailing among American, Russian, Japanese and European contributions, although within the latter group the timbre is very much the same. This is why I have dreamed of a European 'chamber orchestra' in addition to the great world orchestra.

The activities in this book explain elementary concepts in the study of chemistry, including matter, atoms, molecules, physical properties of matter, and changing states of matter. General background information, suggested activities, questions for discussion, and answers are included. Encourage students to keep completed pages in a folder or notebook for further reference and review.

The activities in this book explain elementary concepts in the study of chemistry, including the physical properties of matter (solids, liquids, and gases), surface tension, capillary action, and expansion. General background information, suggested activities, questions for discussion, and answers are included.