[MUSIC]. Good day dear listeners of our course My name is Alexey Tamaskan and I'm professor and head of inorganic chemistry department of San Petersburg State University. It is my pleasure to welcome you to our course, structure over matter from atoms and molecules to materials and nanoparticles. In this course, you will study how we universe is organized. We will start from the small particles atoms, when we consider why atoms attached to each other to form molecules, and when we will move to study materials, nano particles and when applications in different areas of chemistry and technology Universe is very complex. And when scientists describe the universe we use so called models, models is a simplified by but religiously defined view on the matter. So in this course, we will use very simple models One of the most famous models is a model of ideal gas. Every model is based on some postulates ideal gas model based on the following postulates molecules of a gas has have no size way are considered only as a mask points. Collisions between molecules are absolutely elastic and molecules are not interacting with each other. Based on these postulates where mathematical description of a module can be created. This has given us a ideal gas equation. PV equal n RT, where p is a pressure, V is the volume of a system N is amount of substance. R is universal gas constant and T is absolute temperature. Of course, you know what no gas is ideal because every gas has molecules of some size and they interact with each other. However, the ideal gas model describes the behavior of each gas At low pressures and high temperatures, so at pressures less than one atmosphere and temperatures more than 300 Kelvin, any gas can be described successfully by ideal gas equation. So we use the model two Describe behavior over real gas. Another example of modeling chemistry is a model of a pure chemical substance. When we write the chemical equations when we consider what we are doing, we assume what we operate with fewer chemical substances. However, this is not the case. Studies in the Institute of high purity compounds in Russian Academy of Sciences showed what even involved with real high purity germanium Vera Fuji six impurities with large Contamination from 10 to the -8th to 10 to the -13 atomic percent. Why this contamination is large, it looks not so large. But when you consider what, where germanium will be semiconductor if the copper content will be below 10 to the minus 10th atomic percent even realize what in one mole of germanium contains about six to 10 to 11 atoms of copper so it's a lot of atoms in very high purity material. As in in the know the attack. Another noted would in any Bolger on the street, one can find any element Over a periodic system, and this statement is true, where only problem is to find this element and which content it has. So in reality, it's remember, we never worked with pure chemical substances were always impurities in chemicals. We've worked with. Even if it would be no impurities, there is also another obstacle which does not allow us to completely define our chemical system. Let's look for simple water. What is water? What's the formula for it? It's h2o. Everybody knows it. However, we know now what we're hydrogen has two more isotopes. It has not only protein but also the terrarium and tritium and oxygen also have carry oxygen agent isotope Therefore the chemical formulas of water in addition to H2O, it also could be HOD, D2O, H2180, so this called k water and in reality we work with a mixture of isotopes. So it's also One should remember is why this is important. Web impurities are really important and I will tell you two examples why it is important because in the 1970s it was studies of some research groups who claimed what we discovered in a new form of water so called poly water. We distilled and this endlessly water in glass capillaries and were absorbed with the properties of water changed. It became more viscous and it has higher boiling point. Even geriatricians started to predict what is poorly water form might be more stable than normal water. However, in several years, it was disproved. spectroscopiist found mistakes and were assignments into deficiency using by more sophisticated methods showed with normal water. Is most stable. And actually, the polywater was solution of some silicates organic materials which came into the sample upon distilled mints and measurements. So one should really carefully examine what he works with. Another example considering extraction of gold from the seawater. us in any Bolger on the street Also in, in the ocean where every element dissolved, Where the contents of these elements is different So in the beginning of the 20th century, German scientist, gentleman chemist, decided to check if it's economically favorable to extract gold from seawater, they made a laboratory test and it showed what this is very favorable. When we build a factory and during his factory tests, we realized that this is not favorable at all we obtained much less gold than we expected. What is the reason for this? They started to look and we found out what we chemicals which we used. In the laboratory the contaminated by gold. So in essence, we worked with much gold in laboratory. And when we switch to the fabric, we're used to completely different chemicals which were not contaminated by gold, and so with gold amount we Extracted was much less and it was not economical to do it. So these two examples really show what it is important to understand what you never worked with fewer chemical substances.Another interesting point about of water and any other molecule is what the molecules are not regions. You probably know from school but what it is angular molecule you can find what it has certain inter atomic distance and it has a certain valence angle. For example, oxygen hydrogen bond is 0.96 angstroms in this course, we will use With angstrom unit chemists like it and this angstroms 10 to the minus 10th of a meter in international system. So, one may say with what is rigid But no, every molecule undergoes some vibrational modes. For the water molecule were free search modes were to violence vibrations. Violence, vibration is when you elongate or contract the chemical bond. So this violence vibrations can be symmetric when you at the same time elongated the same time contract. Or isometric when one would elongates and one would contracts and what it also undergoes deformation, deformation of vibrations associated with violence and will change. For example, here sewn whiskey stirring vibrations of water When the valence angle decreases and increases, so one should realize what the molecule is not a rigid structure, even at room temperature, or moreover even at zero Kelvin which vibrational modes contributes some part which is called zero point vibrational energy. It should be taken into account. Speaking about the developing on science. man should realize that this process is cyclic. If somebody comes to you and says, I discovered completely new cheerier, which rejects all the previous knowledge, most probably it's not true. Usually scientific developments goes as follows. Chemist work and we discover some experimental data, when somebody starts to think about it, how to rationalize what's within reality between this data and he comes with empirical generalization, empirical means where based on the experiment And when some guy says okay, let's try to describe it in terms of some model. So he developed some postulates of a model, mathematical description, and verts would be called theory. The correct theory should completely describe all No one experimental data. If one experimental fact is not fitting to maturity, which Judy is wrong and it should be at edge developed. However, even if agility is good and all experimental data described with science never stops. And at some point not new experimental data arrive. Which are not fitting to our first theorem what the science should do. Like a person could develop the theory of course will advocate with his theory is right an experimental data. Wrong. However, one of course should check with experimental data. But if where, right when we cheer is wrong and new models should be developed. So the model too, based on new, Postlets usually more expanded and it's mathematical description creates, which you agree to and so on because when USA experimental data came in, This cyclic process of development of science is endless. One should note what we choose religion is a subset of theory to so it does not completely rejects it. It just, theory 2 should describe both old and new experimental data. I swear Russian Nobel prize winner in chemistry. I could emission Nicola Nickel X for a scientist to find the big or small discrepancy is a gift of fortune. One should not let it pass. That's very important because even making very simple experiments, if you find out some discrepancy with. Literature data. You should check it very carefully because this can lead you to development of new teoria as did Nikolai Smirnoff when he developed where theory of chain reactions, for which he got his Nobel prize to give shear Hinshelwood. The example of development of a simple model is the real gas model. We already discussed the ideal gas model, and now the postulates can be changed. Man can postulate that molecules have some size and molecules interact with each other. When one can create more complicated mathematical description of his model, its so called Vander Waals equation is given on the slide. This equation contains two parameters A and B. This parameter is dependent on the nature of a gas In the physical sense parameter B is volume of one molecule because in the total volume of molecules we have size, we have some occupies some volume. So one should take this into account and parameter A is responsible for the interaction between molecules. So, this is more complicated equation, which works in large a temperature and pressure interval. However, please note that if A and B will be equal to zero, this equation converts to ideal gas equation. So, at some conditions, when molecules interaction is very small and the size of a molecule is negligible, you can use more simple equation, ideal gas equation instead of real gas equation. In our courts It's course for beginners. We use very simple models. It's important to understand the limitations of the model. So never use an ideal gas equation for very high pressures and very low temperatures, where result will be absorbed. But if you understand with frameworks Where the model works. You can use it to describe when he.
