My Science School

          Fullerene or buckminsterfullerene is a series of hollow carbon molecules that form either a closed cage or a cylinder. Fullerenes in the form of a closed cage are sometimes called buckyballs whereas cylindrical fullerenes are called carbon nanotubes.

          The first fullerene was discovered in 1985 by the British chemist Sir Harold W. Kroto, Richard E. Smalley and Robert F. Curl, Jr., of the United States. The trios were awarded the Nobel Prize in 1996 for their discovery.

          It is in turn named after the American architect R. Buckminster Fuller, whose geodesic dome is constructed on the same structural principles. Sumio Lijima of Japan identified the elongated cousins of buckyballs called carbon nanotubes in 1991.

         Though fullerenes had been predicted for some time, they were detected in nature and outer space only after their accidental synthesis in 1985. Until then, graphite, diamond, and amorphous carbon such as soot and charcoal were the only allotropes of carbon. The discovery of fullerenes has led to a new understanding of sheet materials and created new vistas in nano-science and nanotechnology.

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          How do we know that dinosaurs lived on Earth millions of years ago? From their fossils of course. But how do we know their age? One way to do it is through radiocarbon dating.

          The ages of objects can be determined by finding out the amount of radiocarbon in it. All living things Contain traces of carbon-14, a radio-active element of carbon. Dating an object with the help of radiocarbon is known as ‘radiocarbon dating’ and it can date objects up to 50,000 years old. Willard Libby first proposed this innovative method for dating organic material in 1946 which is done by determining the half-life of radioactive carbon.

          Carbon-14 is formed when Cosmic rays hit the atmosphere and react with atmospheric nitrogen. Carbon -14 is taken in by plants which in turn enters all living organisms through the food chain. When an animal or a plant dies, carbon-14 atoms decay at a steady rate. The amount of carbon-14 in a dead plant or animal can give us information regarding when it died. The process lies in finding the amount of carbon-14 and dating it using half-life of the element. Half-life is defined as the period of time after which half of a given sample will have decayed. The half-life of carbon-14 is about 5,500 years. This means that after 5,500 years after the death of a plant or an animal, half the carbon-14 atoms at the time of its death won’t be present. Therefore, the lesser the amount of carbon-14, the older the sample.

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          In 1932, James Chadwick became the first person to discover neutrons. Chadwick had experience working with Rutherford, who discovered protons.

          After the discovery of protons, scientists found that protons were not the only particle in the nucleus. The number of protons in the nucleus is called atomic number. It is equal to the positive charge of the atom. During atomic disintegration, scientists were baffled to find that atomic number was less than atomic mass. For example, a helium atom’s mass is four whereas its atomic number is just two.

          Because electrons have almost no mass, scientists assumed that something other than protons were adding to the mass. Chadwick kept this problem in mind even while he was engaged in other matters. He conducted many experiments to find a neutral particle with zero charge that has the same mass as a proton. Finally, Chadwick proved the existence of neutrons and determined that its mass was about 0.1 per cent more than the proton’s. In a characteristic display of modesty, he published his findings in a paper titled Possible Existence of a Neutron. Chadwick was awarded the Nobel Prize in 1935 for his discovery.

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            An isotope is any form of a chemical element that has the same number of protons in the nucleus, or the same atomic number but has a different number of neutrons in the nucleus.

            For example, three isotopes of carbon are found in nature- carbon-12, carbon-13 and carbon-14. All three have six protons, but their neutron numbers differ, being 6, 7, and 8 respectively. Isotopes may be stable or unstable. If unstable, they will be radioactive. The term isotope is a combination of the Greek word ‘isos’, meaning equal, and ‘typos’ which means place.

            Radiochemist Frederick Soddy was the first to suggest the existence of isotopes in 1913. He made this inference based on studies of radioactive decay chains. Soddy was also the first to isolate isotopes by degenerating uranium.

           The first evidence for multiple isotopes of a stable, non-radioactive element was found by J. J. Thomson in 1913. The effect of isotopes on atomic mass was discovered by Harold Urey and G. M. Murphy in 1931.

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          Nitrogen is an essential nutrient for plants. Though four-fifths of air is made up of nitrogen, plants are unable to absorb it directly. To resolve this, plants were given nitrogen-rich fertilizers. By the 1900s however, natural supplies of nitrogen such as bird droppings were in short supply.

           In 1909, German chemist Fritz Haber successfully managed to capture atmospheric nitrogen. Nitrogen was combined with hydrogen under high pressure and heat, to form ammonia which could be made into fertilizers and similar products. This process, known as the Haber process, had potential applications in industrial and agricultural sectors.

          In 1913, a research team from BASF, under the leadership of Carl Bosch developed the first industrial level application of this process, now occasionally called the Haber-Bosch process.

          In the early twenty-first century, the global demand for ammonia was over 100 million tons. The success of the Haber process lies in satisfying about 99 per cent of this demand.

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          John Dalton, J.J. Thomson, Ernest Rutherford, and Niels Bohr were the scientists who made notable contributions towards the study of atomic structure.

          Dalton successfully stated about atoms, but failed to identify the subatomic particles. Sir Joseph John Thomson came up with a model of an atom in the 1900s. He described atom as a positively charged sphere into which negatively charged electrons were embedded. Thomson’s model can be visualised as a plum pudding with the positively charged atom and plum pieces as electrons. Thus, the idea came to be called the ‘plum pudding model.’

          Rutherford was J.J. Thomson’s student. He modified his teacher’s model when another subatomic particle called nucleus was discovered.

          Neils Bohr put forth his model of the atom in 1915. One of the most significant ideas he suggested was that electrons were placed on distinct ‘stationary orbits’ inside the atom.

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          Proton is one of the constituents of an atom, besides neutron and electron. These positively charged protons reside in the nucleus of the atom and add to the overall positive charge of a molecule.

          Ernest Rutherford is generally credited with the discovery of protons. He discovered alpha and beta ‘rays’ from uranium in 1899. The alpha rays were later found to be from the nuclei of helium atoms. In 1919 Rutherford conducted many experiments to explore radioactivity. As a result of one of these experiments, he discovered that atoms have a concentrated positive centre charge which contains most of the mass of that atom.

          Rutherford suggested that the nucleus carried a positively charged particle. He called it proton; a name derived from the Greek word ‘protos’ which means ‘first’. The numbers of protons differ from one element to another thereby giving each nucleus a different charge. This meant that the hydrogen nucleus, which has a single proton, was an elementary particle.

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          Noble gases are a group of chemical elements with similar properties. Six naturally occurring noble gases are helium, neon, argon, krypton, xenon and radioactive radon. As we saw before, helium was first discovered in 1868, while looking at the chromosphere of the Sun and was first isolated by William Ramsay.

          Argon, the lazy one, was discovered by Lord Rayleigh and William Ramsay at University College, London in 1894. It was named so, due to its inert character. Krypton, neon, and xenon were discovered by William Ramsay in 1898. Radon was first identified in 1898 by Friedrich Ernst Dorn. However, it was not considered a noble gas until 1904 when its characteristics were found similar to other noble gases.

          In 1904, Rayleigh and Ramsay received the Nobel Prizes in Physics and in Chemistry respectively for their discovery of the noble gases.

          As these gases occur in smaller amounts in the atmosphere, they are also called rare gases. Helium is found sealed within some of the radioactive minerals and can be released on heating. Others are obtained by fractional distillation of liquid air.

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          Helium was first discovered in the corona surrounding the Sun and later found in gases leaking from Mount Vesuvius. It is the second-most abundant element in the universe.

          The first evidence of helium was observed on 18 August 1868, in the spectrum of the chromosphere of the Sun. It was discovered on Earth much later. Italian physicist Luigi Palmieri detected helium on Earth for the first time through its spectral line in 1881. He found it while analysing a material that had sublimated during a recent eruption of Mount Vesuvius. The first person to isolate helium on Earth was the Scottish chemist, Sir William Ramsay. On 26 March 1895, he heated a mineral called cleveite, which contains uranium and discovered that it gave off a gas. The gas was identified by the yellow line in its spectrum, which matched that of the helium in the Sun.

          The same year, chemists Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden collected enough helium to determine its atomic weight accurately. Later, Ramsay and a British chemist Frederick Soddy discovered that helium is produced whenever radioactive elements decay.

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          Silicon is an element represented as Si. Sir Humphry Davy proposed the name “silicium” for silicon after an attempt to isolate it in 1808.

          In 1811, Gay-Lussac and Louis Thenard are thought to have prepared impure amorphous silicon by heating recently isolated potassium metal with silicon tetrafluoride. They however, did not purify the product, nor did they identify it as a new element. Silicon’s present name was given in 1817 by Scottish chemist Thomas Thomson.

          Jons Jacob Berzelius is credited with the discovery of silicon. In 1824, he used the method followed by Gay-Lussac to prepare amorphous silicon and then purified the product into a brown powder through repeated washing.

          Silicon of lesser purity is used in metallurgy as a reducing agent and as an alloying element in steel, aluminium, brass, and bronze.       

          Silicon dioxide (silica) and various silicates are the most important compounds of silicon. Silica in the form of sand and clay is used to make concrete and bricks. It is also used as refractory material for high-temperature applications.

 

          The fact that blood circulates in our body might seem obvious to us in this age of advanced medical technology, but that was not always the case. Early knowledge of this subject came from the studies of Galen, the Greek physician. Unfortunately, most of his conclusions were later proven wrong.

          It was William Harvey who discovered and published the first accurate description of the human circulatory system in 1616. Before Harvey’s discovery, it was thought that blood was made in the liver which later turned into flesh. Though this might seem stupid to us, it was widely accepted by the doctors back then.

          Harvey accepted only those ideas which had scientific evidence. He finally published his research findings in Exercitatio Anatomica de Motu Cordis Sanguinis in Animalibus (An Anatomical Exercise on the Motion of the Heart and Blood in Living Beings) in 1628. He proved that blood circulates within the body and that the circulatory system includes arteries, veins and the heart.

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          William Harvey’s description of the circulatory system could not explain how blood moved from arteries to veins. This was one of the mysteries solved by the invention of the microscope.

          In 1661, Marcello Malpighi was working in Bologna, Italy when he discovered tiny vessels through which blood travels. These tiny vessels known as capillaries could only be seen using a microscope and they proved to be the missing element in Harvey’s theory.

          Capillaries are the smallest blood vessels in the human body which function as the site of exchange for many substances. While substances such as water, oxygen and glucose exit the body, other items including, water, carbon dioxide, uric acid, lactic acid, urea and creatine enter the bloodstream through capillaries.

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         What are the constituent elements of all living things? This centuries old question was answered only in the 1660s when scientists Anton Van Leeuwenhoek and Robert Hooke discovered cells and their parts.

         While observing a piece of cork, Hooke noticed that it was made of small structures that reminded him of individual rooms. What appeared like rooms to him were called cells. Meanwhile, Anton Van Leeuwenhoek studied substances such as blood and saliva under the microscope. Within these, he observed tiny parts which he named “animalcules” as they resembled animals.

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          Robert Hooke and Anton Van Leeuwenhoek discovered the existence of microscopic organisms between 1665 and 1683. The presentation of the micro fungus Mucor in Hooke’s Micrographia (1665) is the first published depiction of a microorganism. In 1674, Leeuwenhoek became the first person to see the tiny, single-celled protozoa that swim around in ponds and water butts.

          The organisms discovered until then were comparatively larger than those like bacteria, which were even smaller than protozoa. In 1676, Leeuwenhoek made a lens that could magnify up to 280 times. Using this lens, he observed some of the larger types of bacteria collected from his mouth. Leeuwenhoek used certain techniques to watch them. These techniques probably involved lighting the microscopic organisms from a side, so that they would stand out like dust in a sunbeam.

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          We all know that plants cannot live without the sun. Plants around us absorb energy from sunlight to make food from water and carbon dioxide. This process is called photosynthesis. Though this phenomenon has existed since time immemorial, humans were ignorant about it until the 1800s.

          When green plants receive sunlight, they consume higher amount of carbon dioxide than they release. Moreover, they give out more oxygen than they take in.

          When it is dark, they use oxygen and release carbon dioxide like any other animals and humans.

          This process was first described by the Dutch doctor Jan Ingenhousz in 1779 in his book ‘Experiments Upon Vegetables, Discovering Their Great Power of Purifying the Common Air in Sunshine, and of injuring it in the Shade and at Night.’

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