 Welcome to this course on Statistical Mechanics. Statistical mechanics combines two terms, statistics and mechanics and in certain sense they are antithesis of each other. In statistics we deal with very large number of systems or particles or people while mechanics on the other hand is fully deterministic. We start with certain set of conditions and go to the final conclusion. In science mechanics embodies a deterministic science while statistics is based on probability and such concepts. So these are quite in many sense opposite to each other but in statistical mechanics we combine these two different things to build a completely new discipline which aims at explaining what we call large body phenomena, phenomena which originate from combination and interactions of many particles. For example when a ice melts or water goes into the ice this is what we call a large many body phenomena where many molecules, many water molecules combine together to give rise to a beautiful phenomena like freezing and melting or formation of snowflakes same like formation of rain droplets that also is a many body phenomena. These cannot be understood by studying 1 or 2 or 3 or 10 molecules. We have to understand what we call in chemistry is the Avogadro number of molecules. So, these Avogadro number of molecules interact and they cooperate and collectively create a new phenomena. Such kind of phenomena cannot be understood by studying purely mechanistic view like solving Newton's equation. On the other hand just the statistics as we do in economics or in probability theory cannot explain because we have to take into account the how the molecules interact with each other, how molecules talk with each other. So intermolecular interactions or molecules are talking with each other has to be combined with the probabilistic or statistical approach to explain such phenomena and melting of ice, formation of rain drops, for protein folding or drug DNA intercalation, how the chemotherapy drug works, why you need vitamin D or all kinds of very different things that comes to our mind or all kinds of material science. So, statistical mechanics aims at explaining these kind of phenomena. Now, statistical mechanics is one of the two main branches of theoretical science that we have at our disposal across physics, chemistry, biology or material science. The other being the quantum mechanics and we all know the power of quantum mechanics that it played a role in creating of transistors and superconductivity and semiconductors. Similarly, statistical mechanics is at the heart of biology or at the heart of chemical reactions, at the heart of protein folding as I said drug DNA intercalation. So, you need both statistical mechanics and quantum mechanics two together to understand and explain a large number of natural phenomena. So, in this course we want to bring together these two things and try to explain such phenomena as phase transitions, chemical reaction dynamics, polymers and many other subjects. Just like quantum mechanics that is built on solving the Schrodinger equation and then go on doing many other things. In statistical mechanics we start with certain postulates, actually two postulates which are connected by a hypothesis. Build on these two postulates and one hypothesis statistical mechanics sets out to explain the vast majority or vast number of natural phenomena. So, if you start from these basic postulates and slowly build up the whole empire of statistical mechanics you see you appreciate the beauty of it and you the it is an essential science that is required in understand for example, the undergraduate physical chemistry. As I said biophysical chemistry, material science, mineral composition, nucleation of droplets all almost every phenomena that is happening and nature you need statistical mechanics to explain them. So, it is a huge subject which is can go on many years and many semesters a large number of people doing research on that teaching on this. So, this particular course will be aimed at understanding these basic things to advanced undergraduate students, then master students MSc1 and MSc2 and also beginning or starting PhD students. So, we aim at the physicists, physical chemists and material scientists with emphasis on chemistry and material science in this course and we bring all the essential ingredients of statistical mechanics and after developing the from the basic postulates the machinery we apply to understand phase transition, phase equilibrium, polymers, nucleation and many many other things. So, to summarize the main goal of this course of statistical mechanics is to bring home to undergraduate physics and chemistry students and material science students. The scope of the statistical mechanics to explain a very large number of phenomena that the students have studied in their undergraduate studies. For example, the field of binary mixtures, the non-ideality or the chemical kinetics or the electrochemistry or the electrolytes all these things were taught as a phenomological level and however, statistical mechanics provides a microscopic understanding and microscopic explanation as I said starting from intermolecular interactions the fast magnitude and fast amount of phenomena that is going around us in nature. So, I wish you a good journey through this course of statistical mechanics.