Johannes Diderik van der Waals

Johannes Diderik van der Waals was born on November 23, 1837 in Leyden, located in The Netherlands. His parents were Jacobus van der Waals, a carpenter and Elisabeth van den Burg. Without having much money to start with, van der Waals had to work his way up the latter. After completing his elementary education in Leyden, he became a schoolteacher. Having no prior knowledge of classical languages, and being exempt from taking academic examinations, he continued studying at Leyden University in his spare time during 1862 through 1865.

By doing this he was later able to obtain teaching certificates in mathematics and physics. Other successful people that attended the university were the Nobel Prize winners, and great physicists, Albert Einstein and Paul Ehrenfest. The Arabist and Islam expert Christiaan Snouck Hurgronje and the law expert Cornelis van Vollenhoven, were among those who pushed the university into a place of international prominence during the twenties of the twentiest century. In 1864 Johannes was given a job as a teacher at a middle school in Deventer, The Netherlands. He also married Anna Magdalena Smit, who died early.

After that he never married again. They had three daughters and one son. Shortly after their mothers death, their first daughter, Anne Madeleine, ran the house and looked after her father. His other daughter Jacqueline Elisabeth was a teacher of history and a well-known poetess, (form the research Ive done, Ive noticed a lot of information came up regarding her name). His son Johannes Diderik Jr. , was a Professor of Physics at Groningen University, from 1903 to 1908. Activities JohannesVan der Waals enjoyed on his free time were, walking in the country, and reading.

In 1866, he moved to The Hague (the capital of Southern Holland), first as a schoolteacher and later as Director of one of the middle schools in the town. Then later after laws changed, pertaining towards the law, of were university students werent allowed to take examinations because of not completion of taking classical education such as Latin and Greek, van der Waals was able to take them. In 1873 he obtained his doctor’s degree for a thesis certified as Over de Continuteit van den Gas- en Vloeistoftoestand In other words, for his work on the equation of state for gases and liquids.

Which is now known as Van der Waals equation of state. His resulting equation is: In this thesis he composed a proposal stating: that he made an empirical correction to the Equation of State for Ideal Gases (PV = nRT), to make it work for real gases at elevated pressure and flat temperature, where attraction between molecules and their calculable sizes come into play. He could also demonstrate that these two states of matter not only merge into each other in an ongoing process, but that they are in fact of

The momentousness of this conclusion from Van der Waals’ first thesis can be judged from the comments made by Clerk Maxwell. He said, “that there can be no doubt that the name of Van der Waals will soon be among the foremost in molecular science” and “It has certainly directed the attention of more than one inquirer to the study of the Low-Dutch language in which it is written. ” After being appointed as the very first professor of Physics at the University of Amsterdam he accomplished many great tasks.

Along with him accompanied, Vant Hoff and Hugo de Vries, the geneticist, by staying faithful to the university and not leaving until retirement, he helped it become a very popular school. His second great achievement was the Law of Corresponding States It was this law which served as an instructional guide during experiments which ended up to the result of liquefaction of hydrogen by J. Dewar in 1898 and of helium by H. Kamerlingh onnes in 1908. He also was given many awards: Van der Waals was the recipient of numerous honors and distinctions, of which the following should be particularly mentioned.

He received an honorary doctorate of the University of Cambridge; was made honorary member of the Imperial Society of Naturalists of Moscow, the Royal Irish Academy and the American Philosophical Society; corresponding member of the Institut de France and the Royal Academy of Sciences of Berlin; associate member of the Royal Academy of Sciences of Belgium; and foreign member of the Chemical Society of London, the National Academy of Sciences of the U. S. A. , and of the Accademia dei Lincei of Rome. Johannes Diderik van der Waals died in Amsterdam on March 8, 1923. He was 86 years old, when he departed from the world.

He was a man that came from nothing and amounted to a lot because of his ambition and thirst for life. Johannes was a wise man who opened the doors for other scientist, of other racists, genders and of people of different ages. If it wasnt for him or other gifted scientists then we may not have the knowledge or understanding of the world and things around us, that we do today. Johannes Diderik van der waals attained many goals in his life. From starting out with a roof over his head and a carpenter as a father, he was able to achieve a great deal and make history come to life.

After a long struggle to succeed he was able to accomplish many achievements. Two of those were, van der Waals forces, and van der Waals equation of state. Van der Waals forces scientific definition is, a term used to describe the weakest intermolecular attractions; these include dispersion forces and dipole interactions. In English that means, molecules that are attracted to each other at moderate distances and repel each other when at a close range. The forces only operate when the molecules pass very close to each other during collision or scarcely missing.

These occurrences happen during liquefying and solidifying gases, and in almost all organic liquids and solids. Solids that are held together by van der Waals forces generally have lower melting points and are more fragile than those held together by the stronger ionic bond (the electrostatic attraction that binds oppositely charged ions together. ), covalent (a chemical bond formed between atoms by the sharing of electrons), and metallic bonds (the force of attraction that holds metals together; it consists of the attraction of free-floating valence electrons for positively charged metal ions).

It can be seen that as the atomic number and the number of electron increase, the van der Waals forces between them also increase since it takes more energy to do things with them. This analysis is true for all molecules, the bigger they get, and the more electrons that they contain, the more that van der Waals forces will modify them. It is important to remember that van der Waals’ forces are forces that exist between MOLECULES of the same substance. And they are quite different from the forces that make up the molecule.

There are three van der Waals forces: Dipole interactions, Dispersion forces, and hydrogen bonding. Dipole interactions are one of van der Waals’ three forces. They exist between any two polar molecules: the negatively charged end of one molecule attracts the positive end of another molecule. Polar molecules have an unequal sharing of electrons. The molecules naturally familiarize themselves to accommodate the charge. The positive part of one molecule will move until it is next to the negative part of a neighboring molecule. These forces between molecules tend to make them literally, ‘stick’ together.

Or this analogy might make more sense; one end of the molecule with the atom having the greater ability to attract electrons will be slightly negative and the other end will be slightly positive. Thats where the Dipole force comes into action, one end is slightly negative and the other end of it is slightly positive. The Dispersion forces exist between non-polar molecules. Dispersion forces are another of van der Waals’ three forces. They exist between non-polar molecules. It is important to remember that within a bond, electrons are constantly MOVING. They zoom around the atoms really quickly.

As a result, there may be a tiny instant in that time span where the electrons happen to dominant on one side, rather than the other. However, this temporary charge disappears just as quickly as it appeared because the electrons are moving so fast that it really doesnt matter. These temporary dipoles allow the negative side of one molecule to attract the positive side of another molecule, which is the intermolecular force. The energy required to separate and move molecules from one another increases as the size of the molecules becomes greater in size.

Since it takes energy to separate the molecules, the attraction between molecules is greater. Dispersion forces are also the type of intermolecular forces responsible for the increase in melting points and boiling points of these non-polar covalent compounds. The last of van der Waals forces is Hydrogen bonding or a shared electron bond. Hydrogen bonding by scientific is a relatively strong intermolecular force in which a hydrogen atom that is covalently bonded to a very electronegative atom is also weakly bonded to an unshared electron pair of an electronegative atom in the same molecule or one nearby.

Hence the name, hydrogen bonding, ALWAYS involves with the element hydrogen. As it states in our chemistry book, it is the only chemically reactive element whose valence electrons are not shielded from the nucleus by a layer of underlying electrons. Since hydrogen is the smallest atom on the periodic table, its easy to understand that two molecules can get very close to each other. They are approximately 30 times smaller than normal colvalent bonds. When I stated previously that Dipole interactions are small, hydrogen bonding is much smaller, it literally dwarfs it.

Hydrogen bonds vary from about 4 kJ/mole to 25 kJ/mole (so they are still weaker than typical covalent bonds. But they are stronger than dipole-dipole and or dispersion forces). Hydrogen bonds only form between hydrogen and the element nitrogen, oxygen, or not as common fluorine. These elements are very electronegative, that is, when they form a covalent bond with hydrogen. What they do is pull hydrogen’s single electron more tensely toward them and away from hydrogens nucleus. This creates a slight positive charge on the hydrogen atom and also a negative charge on the oxygen, nitrogen, or fluorine atom.

If the word electronegativity seems unfamiliar to you, it means having a tendency to attract electrons. The hydrogen’s proton and its positive charge are bared. When the slightly positively charged hydrogen draws towards a slightly negatively charged oxygen, nitrogen, or fluorine atom in another molecule, the two atoms form what is called, a hydrogen bond. These special bonds are important for the living system. Hydrogen bonds are the foundation of keeping water molecules together in the liquid state. It helps prevent the water molecules from separating and being evaporated.

Without hydrogen bonds, water would boil close to 80 C instead of at 100 C. Also, water in the state of liquid would not exist in most places on Earth. Hydrogen bonds also make up DNA by binding together the paired strands of compounds. The van der waals equation was developed in 1873, when Johannes van der Waals made his Ph. D. thesis. His equation of state was the very first to describe the critical point and phase separation. His equation was developed to serve two purposes one was to show that the volume of molecules reduces the amount of free volume floating in a fluid.

His second purpose was to show that the attraction of the molecules produced another additional pressure. Johannes van der Waals equation of state looks like this: He arrived at this conclusion by probably one day looking at the ideal gas equation, and figuring something was not correct about it. The ideal gas equation is Pv = nRT. The ideal gas equation states the realationship between pressure, volume, temperature and the number of particles that a gas contains. The ideal gas equation made some statements that were not true.

Molecules do have volume and do attract each other. all gases depart from ideal behavior under conditions of low temperature.. and high pressure. In the equation of state he said that since ther are attractive forces between molecules, the pressure is lower than the ideal value. Basically van der Waals equation is a modified version of this one. The importance of this thesis was described when a man by the name of dames Clerk Maxwell in Nature said a very important statement.

He said, “that there can be no doubt that the name of Van der Waals will soon be among the foremost in molecular science” and “It has certainly directed the attention of more than one inquirer to the study of the Low-Dutch language in which it is written. ” It should be brought up that the van der Waals equation is not perfectly accurate but is historically important and practical for qualitative investigations. At the moment there are hundreds of different equations of states out theyre which have been developed empirically or theoretically for lots of substances.


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