Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.



Published on

Published in: Education, Technology
  • Be the first to comment

  • Be the first to like this


  1. 1. G Gamma Ray Gamma radiation, also known as gamma rays, and denoted by the Greek letter γ, refers to electromagnetic radiation of extremely high frequency and therefore high energy per photon. Gamma rays are ionizing radiation, and are thus biologically hazardous. They are classically produced by the decay from high energy states of atomic nuclei (gamma decay), but are also created by other processes. Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium. Villard's radiation was named "gamma rays" by Ernest Rutherford in 1903. Natural sources of gamma rays on Earth include gamma decay from naturally occurring radioisotopes, and secondary radiation from atmospheric interactions with cosmic ray particles. Rare terrestrial natural sources produce gamma rays that are not of a nuclear origin, such as lightning strikes and terrestrial gamma-ray flashes. The electron avalanche builds up quickly, generating more and more high energy particles, in an ever increasing feedback loop, eventually generating a terrestrial gamma ray flash. Gamma rays are produced by a number of astronomical processes in which very high-energy electrons are produced, that in turn cause secondary gamma rays by the mechanisms of Gamma Ray Radiation
  2. 2. bremsstrahlung, inverse Compton scattering and synchrotron radiation. A large fraction of such 41 astronomical gamma rays are screened by Earth's atmosphere and can only be detected by spacecraft. Gamma rays typically have frequencies above 10 exahertz (or >1019 Hz), and therefore have energies above 100 keV and wavelengths less than 10 picometers (less than the diameter of an atom). However, this is not a hard and fast definition, but rather only a rule-of-thumb description for natural processes. Gamma rays from radioactive decay are defined as gamma rays no matter what their energy, so that there is no lower limit to gamma energy derived from radioactive decay. Gamma decay commonly produces energies of a few hundred keV, and almost always less than 10 MeV. In astronomy, gamma rays are defined by their energy, and no production process need be specified. The energies of gamma rays from astronomical sources range over 10 TeV, at a level far too large to result from radioactive decay. [2] A notable example is extremely powerful bursts of high-energy radiation normally referred to as long duration gamma-ray bursts, which produce gamma rays by a mechanism not compatible with radioactive decay. These bursts of gamma rays, thought to be due to the collapse of stars called hypernovae, are the most powerful events so far discovered in the cosmos. Geiger, Hans Wilhelm ( 1882-1945) September 30, 1882, Neustadt an de Haardt, Germany, d. September 24, 1945, Potsdam. A German physicist and inventor of the Geiger counter, a type of particle detector, and for the Geiger-Marsden experiment which discovered the atomic nucleus. In 1902 , Geiger started studying physics and mathematics in the University of Erlangen and was awarded a doctorate in 1986. In 1907 he began work with Ernest Rutherford at the Hans Wilhelm "Gengar" Geiger (1928)
  3. 3. University of Manchester, the following year he built his first device to detect radioactive 42 particles and became known as Geiger Counter. The detection component ofGeiger Counter as a metal tube filled with gas under low pressure. The tube and a copper cathodes are under high voltage. When alpha particle emitted from the nucleus of a radioactive atom passes through the tube, it ionizes a gas molecule leaving the molecule or ion, is then attracted to the cathode. As it moves toward the cathode, the ion collides with other gas molecule s and produces more ions. This brief cascade of ions creates sufficient energy to produce a momentarily electrical current. The Geiger Counter records each cascade electronically and indicates a cascade with a click. Rapidly repeating clicks indicates the presence or a huge number of alpha particles and therefore an increased level of radioactivity. Rutherford subsequently identified the alpha particles as the nucleus of helium atom. In 1909, along with Ernest Marsden, conducted the famous Geiger- Marsden experiment, also called the ― gold-foil experiment‖. And also along with Ernest Rutherford, they created the Rutherford-Geiger tube, later to become Geiger counter. In 1911, Geiger and John Mitchel Nuttall discovered the Geiger-Nuttall law and performed experiments that led to Rutherford’s atomic model. In 1928, Geiger and his student, Walter Muller created an improved version of Geiger counter, called as the Geiger-Muller counter. Geiger also worked with James Chadwick. In 1912, leader became the leader of the Physical-Technical Reichsanstalt in Berlin. In 1925, became professor in Kiel, in 1929 in Tubingen and from 1936 in Berlin. He was a member of Uranium Club. He expressed himself in public about the Nazis. But illness slowed the pace of Geiger’s work from 1940 until his death. Giauque, William Francis (1895-1982) b. May 12, 1895 On t. , Canada, d. March 28, 1982, Berkeley, California, U.S.A. Geiger, Hans Wilhelm
  4. 4. A Canadian- born American physical chemist and winner at the Nobel Prize for chemistry in 1949 for his studies of the properties of matter at temperatures close 43 to absolute zero. After earning his Ph. D. from the University of California, Berkeley in 1922, Giauque joined the chemistry faculty there and held posts at the school until 1981. In 1927, he proposed a new method of achieving extremely low temperatures using a process called adiabatic demagnetization. By 1933, he had working apparatus that obtained a temperature with one-tenth of a degree of absolute zero ( -273.15 degree Celsius). His researched confirmed the third law of thermodynamics, which states that the entropy of ordered solids reaches zero at the absolute zero of temperature. In the course of his low-temperature studies of oxygen, Giauque discovered with Herrick L. Johnston the oxygen isotopes of mass 17 and 18. For his work in chemical thermodynamics, he received the 1949 Nobel Prize in Chemistry. Gummite It is a mixture of natural Uranium oxides, representing the final oxidation and hydration stages of uraninite, that usually occurs as dense masses and crusts in many of the known uraninite localities. It is named for its gum-like consistence. The material was also known under various names, mostly because of different origins of the samples, including: eliasite from Elias – the name of a mine at Jáchymov, coracite – a variety from Lake Superior, pittinite, pechuran, urangummit and uranogummite. It varies widely in physical appearance of some varieties, is related to well-defined Uranium oxides such as limonite and also manganese oxides. Gummite from collection of Prague National Museum
  5. 5. 44 Gyroscope A gyroscope is a device for measuring or maintaining orientation, based on the principles of angular momentum. Mechanically, a gyroscope is a spinning wheel or disc in which the axle is free to assume any orientation. Although this orientation does not remain fixed, it changes in response to an external torque much less and in a different direction than it would with the large angular momentum associated with the disc's high rate of spin and moment of inertia. The device's orientation remains nearly fixed, regardless of the mounting platform's motion, because mounting the device in a gimbal minimizes external torque. Gyroscopes based on other operating principles also exist, such as the electronic, microchip-packaged MEMS gyroscope devices found in consumer electronic devices, solid-state ring lasers, fibre optic gyroscopes, and the extremely sensitive quantum gyroscope. Applications of gyroscopes include inertial navigation systems where magnetic compasses would not work (as in the Hubble telescope) or would not be precise enough (as in ICBMs), or for the stabilization of flying vehicles like radio-controlled helicopters or unmanned aerial vehicles. Due to their precision, gyroscopes are also used in gyrotheodolites to maintain direction in tunnel mining.
  6. 6. 45 H Heart The heart is a hollow muscular organ that pumps blood throughout the blood vessels to various parts of the body by repeated, rhythmic contractions. It is found in all animals with a circulatory system, which includes the vertebrates. The adjective cardiac means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart". Cardiology is the medical speciality that deals with cardiac diseases and abnormalities. The vertebrate heart is principally composed of cardiac muscle and connective tissue. Cardiac muscle is an involuntary striated muscle tissue specific to the heart and is responsible for the heart's ability to pump blood. The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during an average 66 year lifespan, and pumps approximately 4.7-5.7 litres of blood per minute. It weighs approximately 250 to 300 grams (9 to 11 oz) in females and 300 to 350 grams (11 to 12 oz) in males. The structure of the heart can vary among the different animal species.Cephalopods have two "gill hearts" and one "systemic heart". In vertebrates, the heart lies in the anterior part of the body cavity, dorsal to the gut. It is always surrounded by a pericardium, which is usually a distinct structure, but may be continuous with the peritoneum in jawless and cartilaginous fish. Hagfish, uniquely among vertebrates, also possess a second heart-like structure in the tail. Structure diagram of the human heart from an anterior view. Blue components indicate deoxygenated blood pathways and red components indicate oxygenated pathways.
  7. 7. The adult human heart has a mass of between 250 and 350 grams 46 and is about the size of a fist. It is located anterior to the vertebral column and posterior to the sternum. It is enclosed in a double-walled sac called the pericardium. The pericardium's outer wall is called the parietal pericardium and the inner one the visceral pericardium. Between them there is some pericardial fluid which functions to permit the inner and outer walls to slide easily over one another with the heart movements. Outside the parietal pericardium is a fibrous layer called thefibrous pericardium which is attached to the mediastinal fascia. This sac protects the heart and anchors it to the surrounding structures. The outer wall of the human heart is composed of three layers; the outer layer is called the epicardium, or visceral pericardium since it is also the inner wall of the pericardium. The middle layer is called the myocardium and is composed of contractile cardiac muscle. In mammals, the function of the right side of the heart is to collect de-oxygenated blood, in the right atrium, from the body (via superior and inferior vena cavae) and pump it, through the tricuspid valve, via the right ventricle, into the lungs (pulmonary circulation) so that carbon dioxide can be exchanged for oxygen. This happens through the passive process of diffusion. The left side (see left heart) collects oxygenated blood from thelungs into the left atrium. From the left atrium the blood moves to the left ventricle, through the bicuspid valve (mitral valve), which pumps it out to the body (via the aorta). On both sides, the lower ventricles are thicker and stronger than the upper atria. The muscle wall surrounding the left ventricle is thicker than the wall surrounding the right ventricle due to the higher force needed to pump the blood through the systemic circulation.
  8. 8. 47 Heat Energy Heat energy is a form of energy that results from movement of atoms, ions or molecules in solids liquids or gases. It can be transferred from one object to another if the two objects have a temperature difference. Thermal energy is generated and measured by heat of any kind. It is caused by the increased activity or velocity of molecules in a substance, which in turn causes temperature to rise accordingly. There are many natural sources of thermal energy on Earth, making it an important component of alternative energy. Heat energy is the type of energy that is emitted from burning fuel. A unit of heat energy is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. Heat energy deals with the transfer of energy of a body or of a system in the form of heat, or raising temperatures. Raising the temperature of a substance, raises it's heat energy. The movement of atoms and molecules create heat energy. It transfers among particles in a give substance by kinetic energy which means that the heat is transferred by bouncing particles bumping into each other. Hemoglobin Hemoglobin (/hiːməːɡloʊbɪn/); also spelled haemoglobin and abbreviated Hb or Hgb, is the iron-containing oxygen- transport metalloproteinase in the red blood cells of all vertebrates[1] (with the exception of the fish family
  9. 9. 48 Channichthyidae) as well as the tissues of some invertebrates. Hemoglobin in the blood carries oxygen from the respiratory organs (lungs or gills) to the rest of the body (i.e. the tissues) where it releases the oxygen to burn nutrients to provide energy to power the functions of the organism in the process called metabolism. In mammals, the protein makes up about 96% of the red blood cells' dry content (by weight), and around 35% of the total content (including water. Hemoglobin has an oxygen binding capacity of 1.34 mL O2 per gram of hemoglobin, which increases the total blood oxygen capacity seventy-fold compared to dissolved oxygen in blood. The mammalian hemoglobin molecule can bind (carry) up to four oxygen molecules. Hemoglobin is involved in the transport of other gases: it carries some of the body's respiratory carbon dioxide (about 10% of the total) ascarbaminohemoglobin, in which CO2 is bound to the globin protein. The molecule also carries the important regulatory molecule nitric oxide bound to a globin protein thiol group, releasing it at the same time as oxygen. Hemoglobin and hemoglobin-like molecules are also found in many invertebrates Hemoglobin is also found outside red blood cells and their progenitor lines. Other cells that contain hemoglobin include the A9 dopaminergic neurons in the substantial nigra, macrophages, alveolar cells, and meningeal cells in the kidney. In these tissues, hemoglobin has a non-oxygen-carrying function as an antioxidant and a regulator of iron metabolism. In these organisms, hemoglobin’s may carry oxygen, or they may act to transport and regulate other things such as carbon dioxide, nitric oxide, hydrogen sulfide and sulfide. A variant of the molecule, called leg hemoglobin, is used to scavenge oxygen away from anaerobic systems, such as the nitrogen-fixing nodules of leguminous plants, before the oxygen can poison the system. Hemoglobin consists mostly of protein subunits (the "globin" molecules), and these proteins, in turn, are folded chains of a large number of different amino acids called polypeptides. The amino acid sequence of any polypeptide created by a cell is in turn determined by the stretches of DNA called genes. In all proteins, it is the amino acid sequence which determines the protein's chemical properties and function. There is more than one hemoglobin gene. The amino acid sequences of the globin proteins in hemoglobins usually differ between species. These differences grow with evolutionary distance
  10. 10. 49 between species. For example, the most common hemoglobin sequences in humans and chimpanzees are nearly identical, differing by only one amino acid in both the alpha and the beta globin protein chains. These differences grow larger between less closely related species. Even within a species, different variants of hemoglobin always exist, although one sequence is usually a "most common" one in each species. Mutations in the genes for the hemoglobin protein in a species result in hemoglobin variants. Many of these mutant forms of hemoglobin cause no disease. Some of these mutant forms of hemoglobin, however, cause a group of hereditary diseases termed the hemoglobinopathies. The best known hemoglobinopathy is sickle-cell disease, which was the first human disease whose mechanism was understood at the molecular level. A (mostly) separate set of diseases called thalassemias invol ves underproduction of normal and sometimes abnormal hemoglobins, through problems and mutations in globin gene regulation. All these diseases produce anemia. Variations in hemoglobin amino acid sequences, as with other proteins, may be adaptive. For example, recent studies have suggested genetic variants in deer mice that help explain how deer mice that live in the mountains are able to survive in the thin air that accompanies high altitudes. Hydroelectricity Use running water to generate electricity, whether it's a small stream or a larger river. Small or micro hydroelectricity systems, also called hydropower systems or just hydro systems, can produce enough electricity
  11. 11. 50 for lighting and electrical appliances in an average home. How do hydropower systems work? All streams and rivers flow downhill. Before the water flows down the hill, it has potential energy because of its height. Hydro power systems convert this potential energy into kinetic energy in a turbine, which drives a generator to produce electricity. The greater the height and the more water there is flowing through the turbine, the more electricity can be generated. The amount of electricity a system actually generates also depends on how efficiently it converts the power of the moving water into electrical power. Hydrogen Bond Polar molecules, such as water molecules, have a weak, partial negative charge at one region of the molecule (the oxygen atom in water) and a partial positive charge elsewhere (the hydrogen atoms in water). Thus when water molecules are close together, their positive and negative regions are attracted to the oppositely-charged regions of nearby molecules. The force of attraction, shown here as a dotted line, is called
  12. 12. 51 a hydrogen bond. Each water molecule is hydrogen bonded to four others. The hydrogen bonds that form between water molecules account for some of the essential — and unique — properties of water. The attraction created by hydrogen bonds keeps water liquid over a wider range of temperature than is found for any other molecule its size. The energy required to break multiple hydrogen bonds causes water to have a high heat of vaporization; that is, a large amount of energy is needed to convert liquid water, where the molecules are attracted through their hydrogen bonds, to water vapor, where they are not. Two outcomes of this: The evaporation of sweat, used by many mammals to cool themselves, cools by the large amount of heat needed to break the hydrogen bonds between water molecules. Reduction of temperature extremes near large bodies of water like the ocean. The hydrogen bond has only 5% or so of the strength of a covalent bond. However, when many hydrogen bonds can form between two molecules (or parts of the same molecule), the resulting union can be sufficiently strong as to be quite stable. Multiple hydrogen bonds hold the two strands of the DNA double helix together hold polypeptides together in such secondary structures as the alpha helix and the beta conformation; help enzymes bind to their substrate help antibodies bind to their antigen help transcription factors bind to each other; help transcription factors bind to DNA
  13. 13. 52 I Ionic Bonding Ionic bonding is a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions. These ions represent atoms that have lost one or more electron (known as cations) and atoms that have gained one or more electrons (known as an anions). In the simplest case, the cation is a metal atom and the anion is a nonmetal atom, but these ions can be of a more complex nature, e.g. molecular ions like NH4 + or SO4 2- It is important to recognize that clean ionic bonding - in which one atom "steals" an electron from another - cannot exist: All ionic compounds have some degree of covalent bonding, or electron sharing. Thus, the term "ionic bonding" is given when the ionic character is greater than the covalent character - that is, a bond in which a large electronegativity difference exists between the two atoms, causing the bonding to be more polar (ionic) than in covalent bonding where electrons are shared more equally. Bonds with partially ionic and partially covalent character are called polar covalent bonds. Ionic compounds conduct electricity when molten or in solution, but typically not as a solid. There are exceptions to this rule, such as rubidium silver iodide, where the silver ion can be quite mobile. Ionic compounds generally have a high melting point, depending on the charge of the ions they consist of. The
  14. 14. higher the charges the stronger the cohesive forces and the higher the melting point. They also tend to be soluble in water. 53 Here, the opposite trend roughly holds: The weaker the cohesive forces the greater the solubility. Formation Ionic bonding can result from a redox reaction when atoms of an element (usually metal), whose ionization energy is low, release some of their electrons to achieve a stable electron configuration. In doing so, cations are formed. The atom of another element (usually nonmetal), whose electron affinity is positive, then accepts the electron(s), again to attain a stable electron configuration, and after accepting electron(s) the atom becomes an anion. Typically, the stable electron configuration is one of the noble gases for elements in the s-block and the p- block, and particular stable electron configurations for d-block and f-block elements. The electrostatic attraction between the anions and cations leads to the formation of a solid with a crystallographic lattice in which the ions are stacked in an alternating fashion. In such a lattice, it is usually not possible to distinguish discrete molecular units, so that the compounds formed are not molecular in nature. However, the ions themselves can be complex and form molecular ions like the acetate anion or the ammonium cation. Insulin Insulin is a peptide hormone, produced by beta cells of the pancreas, and is central to regulating carbohydrate and fat metabolism in the body. It causes cells in the liver, skeletal muscles, and fat tissue to absorb glucose from the blood. Insulin stops the use of fat as an energy source by inhibiting the release of glucagon. With the exception of the metabolic disorder diabetes mellitus and metabolic syndrome, insulin is provided within the body in a constant proportion to remove
  15. 15. excess glucose from the blood, which otherwise would be toxic. When blood glucose levels fall below a certain level, the 54 body begins to use stored sugar as an energy source through glycogenolysis, which breaks down the glycogen stored in the liver and muscles into glucose, which can then be utilized as an energy source. As a central metabolic control mechanism, its status is also used as a control signal to other body systems (such as amino acid uptake by body cells). In addition, it has several other anabolic effects throughout the body. When control of insulin levels fails, diabetes mellitus can result. As a consequence, insulin is used medically to treat some forms of diabetes mellitus. Patients with type 1 diabetes depend on external insulin (most commonly injected subcutaneously) for their survival because the hormone is no longer produced internally.[2] Patients with type 2 diabetes are often insulin resistant and, because of such resistance, may suffer from a "relative" insulin deficiency. Some patients with type 2 diabetes may eventually require insulin if other medications fail to control blood glucose levels adequately. Over 40% of those with Type 2 diabetes require insulin as part of their diabetes management plan. The human insulin protein is composed of 51 amino acids, and has a molecular weight of 5808 Da. It is a dimer of an A-chain and a B-chain, which are linked together by disulfide bonds. Insulin's name is derived from the Latin insula for "island". Insulin's structure varies slightly between species of animals. Insulin from animal sources differs somewhat in "strength" (in carbohydrate metabolism control effects) from that in humans because of those variations. Porcine insulin is especially close to the human version. Synthesis Insulin is proIn mammals, insulin is synthesized in the pancreas within the β-cells of the islets of Langerhans. One million to three million islets of Langerhans (pancreatic islets) form the endocrine part of the pancreas, which is primarily an exocrine gland. The endocrine portion accounts for only 2% of the total mass of the pancreas. Within the islets of Langerhans, beta cells constitute 65–80% of all the cells.
  16. 16. Insulin consists of two polypeptide chains, the A- and B- chains, linked together by disulfide bonds. It is however first synthesized as a single polypeptide called preproinsulin in 55 pancreatic β-cells. Preproinsulin contains a 24-residue signal peptide which directs the nascent polypeptide chain to the rough endoplasmic reticulum (RER). The signal peptide is cleaved as the polypeptide is translocated into lumen of the RER, forming proinsulin.[13] In the RER the proinsulin folds into the correct conformation and 3 disulfide bonds are formed. About 5–10 min after its assembly in the endoplasmic reticulum, proinsulin is transported to the trans-Golgi network (TGN) where immature granules are formed. Transport to the TGN may take about 30 min. In the posttranslational modifications insulin and its related proteins have been shown to be produced inside the brain, and reduced levels of these proteins are linked to Alzheimer's disease. duced in the pancreas and released when any of several stimuli are detected. These stimuli include ingested protein and glucose in the blood produced from digested food. Carbohydrates can be polymers of simple sugars or the simple sugars themselves. If the carbohydrates include glucose, then that glucose will be absorbed into the bloodstream and blood glucose level will begin to rise. In target cells, insulin initiates a signal transduction, which has the effect of increasing glucose uptake and storage. Finally, insulin is degraded, terminating the response. Iron Iron is a chemical element with the symbol Fe (from Latin: ferrum) and atomic number 26. It is a metal in the first transition series. It by mass is the most common element on Earth, forming much of Earth's outer and inner core. It is the fourth most 1lustrous metallic with a grayish tinge
  17. 17. common element in the Earth's crust. Iron's very common presence in rocky planets like Earth is due to its abundant production as a result of fusion in high-mass stars, wherein the production of nickel-56 (which decays to the most common isotope of iron) is 56 the last nuclear fusion reaction that is exothermic. Therefore, radioactive nickel is the last element to be produced, before collapse of a supernova causes the explosion that abundantly scatters this precursor radionuclide into space. Like other group 8 elements, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen and water. Fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike many other metals which form passivating oxide layers, iron oxides occupy more volume than iron metal, and thus iron oxides flake off and expose fresh surfaces for corrosion. Iron metal has been used since ancient times, though copper alloys, which have lower melting temperatures, were used first in history. Pure iron is soft (softer than aluminium), but is unobtainable by smelting. The material is significantly hardened and strengthened by impurities, such as carbon, from the smelting process. A certain proportion of carbon (between 0.002% and 2.1%) produces steel, which may be up to 1000 times harder than pure iron. Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, which has a high carbon content. Further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and low carbon iron alloys along with other metals (alloy steels) are by far the most common metals in industrial use, due to their great range of desirable properties and the abundance of iron. Iron chemical compounds, which include ferrous and ferric compounds, have many uses. Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. It forms binary compounds with the halogens and the chalcogens. Among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with molecular oxygen in hemoglobin and myoglobin; these two
  18. 18. compounds are common oxygen transport proteins in vertebrates. Iron is also the metal used at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals. 57 Isomer In chemistry, isomers (/ːaɪsəmərz/; from Greek ἰ ζομερής, isomerès; isos = "equal", méros = "part") are molecules with the same molecular formula but different chemical structures. That is, isomers contain the same number of atoms of each element, but have different arrangements of their atoms in space.[1][2] Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like positional isomers, cis-trans isomers and enantiomers, etc. (see chart below). There are two main forms of isomerism: structural isomerism and stereoisomerism (spatial isomerism) Structural isomers In structural isomers, sometimes referred to as constitutional isomers, the atoms and functional groups are joined together in different ways. Structural isomers have different IUPAC names and may or may not belong to the same functional group.[3] This group includes chain isomerism whereby hydrocarbon chains have variable amounts of branching; position isomerism, which deals with the position of a functional group on a chain; and
  19. 19. functional group isomerism, in which one functional group is split up into different ones. For example, two position isomers would be 2-fluoropropane and 1-fluoropropane, illustrated on the left side of the diagram above. 58 In skeletal isomers the main carbon chain is different between the two isomers. This type of isomerism is most identifiable in secondary and tertiary alcohol isomers. Tautomers are structural isomers of the same chemical substance that spontaneously interconvert with each other, even when pure. They have different chemical properties and, as a consequence, distinct reactions characteristic to each form are observed. If the interconversion reaction is fast enough, tautomers cannot be isolated from each other. An example is when they differ by the position of a proton, such as in keto/enol tautomerism, where the proton is alternately on the carbon or oxygen. Stereoisomer In stereoisomers the bond structure is the same, but the geometrical positioning of atoms and functional groups in space differs. This class includes enantiomers, which are non-superimposable mirror-images of each other, and diastereomers, which are not. Enantiomers always contain chiral centres and diastereomers often do, but there are some diastereomers that neither are chiral nor contain chiral centers.[4] Another type of isomer, conformational isomers (conformers), may be rotamers, diastereomers, or enantiomers depending on the exact compound. For example, ortho- position- locked biphenyl systems have enantiomers. E/Z isomers, which have restricted rotation within the molecule, to be specific isomers containing a double bond, are configurational isomers. They are classified as diastereomers, whether or not they contain any chiral centres.[4] E/Z notation depicts absolute stereochemistry, which is an unambiguous descriptor based on CIP priorities. "Cis–trans isomers" are used to describe any molecules with restricted rotation in the molecule. However, these descriptors describe relative stereochemistry only based on group bulkiness or principal carbon chain, so can be ambiguous. This is especially problematic for double bonds that have more than two substituents. An obsolete term for cis–trans isomerism is
  20. 20. "geometric isomerism".[5] For alkenes with more than two substituents, E-Z notation is used instead of cis and trans. If possible, E and Z (written in italic type) is also preferred in compounds with two substituents.[6] In octahedral coordination compounds, facial–meridional isomerism occurs. The isomers can be fac- (with facial ligands) 59 or mer- (with meridional ligands). Note that, although conformers can be referred to as stereoisomers, they are not stable isomers, since bonds in conformers can easily rotate, thus converting one conformer to another, which can be either diastereomeric or enantiomeric to the original one. While structural isomers typically have different chemical properties, stereoisomers behave identically in most chemical reactions, except in their reaction with other stereoisomers. Enzymes, however, can distinguish between different enantiomers of a compound, and organisms often prefer one isomer over the other. Some stereoisomers also differ in the way they rotate polarized light. Isomerization Isomerization is the process by which one molecule is transformed into another molecule that has exactly the same atoms, but the atoms are rearranged.[7] In some molecules and under some conditions, isomerization occurs spontaneously. Many isomers are equal or roughly equal in bond energy, and so exist in roughly equal amounts, provided that they can interconvert relatively freely, that is the energy barrier between the two isomers is not too high. When the isomerization occurs intramolecularly, it is considered a rearrangement reaction. An example of an organometallic isomerization is the production of decaphenylferrocene, [(η5 -C5Ph5)2Fe] from its linkage isomer.[8][9]
  21. 21. 60 J Jade Jade is an ornamental rock. The term jade is applied to two different metamorphic rocks that are made up of different silicate minerals: Nephrite consists of a microcrystalline interlocking fibrous matrix of the calcium, magnesium-iron rich amphibole mineral series tremolite (calcium-magnesium)-ferroactinolite (calcium- magnesium-iron). The middle member of this series with an intermediate composition is called actinolite (the silky fibrous mineral form is one form of asbestos). The higher the iron content the greener the colour. Jadeite Jadeite is a sodium- and aluminium-rich pyroxene. The gem form of the mineral is a microcrystalline interlocking crystal
  22. 22. matrix. A high pressure clinopyroxene that is frequently carved and polished as a gemstone. Jadeite is a pyroxene mineral with composition NaAlSi2O6. It is monoclinic. It has a Mohs hardness of about 6.5 to 7.0 61 depending on the composition. The mineral is dense, with a specific gravity of about 3.4. Jadeite forms solid solutions with other pyroxene endmembers such asaugite and diopside (CaMg-rich endmembers), aegirine (NaFe endmember), and kosmochlor (NaCr endmember). Pyroxenes rich in both the jadeite and augite endmembers are known as omphacite. Jasper A variety of colored chert, typically red or green and often found in association with iron ores. Jasper is frequently used as a gemstone or in the production of ornaments. The name means "spotted or speckled stone", and is derived via Old French jaspre (variant of Anglo-Norman jaspe) and Latin iaspidem (nom. iaspis)) from Greek ἴ αζπις iaspis, (feminine noun)[5] from a Semitic language (cf. Hebrew ‫יושפה‬yushphah, Akkadian yashupu). Green jasper was used to make bow drills in Mehrgarh between 4th and 5th millennium BC. Jasper is known to have been a favorite gem in the ancient world; its name can be traced back in Arabic, Persian, Hebrew, Assyrian, Greek and Latin. On Minoan Crete,
  23. 23. jasper was carved to produce seals circa 1800 BC, as evidenced by archaeological recoveries at the palace of Knossos. 62 Jolly Balance The Jolly balance is an instrument for determining specific gravities. Invented by the German physicist Philipp von Jolly in 1864, it consists of a spring fastened at the top to a movable arm. At the lower end, the spring is provided with two small pans, one suspended beneath the other. The lower pan is kept immersed to the same depth in water, while the other one hangs in the air. On the upright stand behind the spring is a mirror on which is engraved or painted a scale of equal parts. The specific gravity of an object, typically a solid, is determined by noting how much the spring lengthens spring when the object is resting in the upper pan in air ( ), and then when the object is moved to the lower pan and immersed in water ( ). The specific gravity is . Juvenile water or Magmatic water A spring balance used in the determination of specific gravity. Magmatic water or juvenile water is water that exists within, and in equilibrium with, a magma or water rich volatile fluids that are derived from a magma. This
  24. 24. magmatic water is released to the atmosphere during a volcanic eruption. Magmatic water may also be released as hydrothermal fluids during 63 the late stages of magmatic crystallization or solidification within the Earth's crust. The crystallization of hydroxyl bearing amphibole and mica minerals acts to contain part of the magmatic water within a solidified igneous rock. Ultimate sources of this magmatic water includes water and hydrous minerals in rocks melted during subduction as well as primordial water brought up from the deep mantle. Juvenile Water: Water that is new to the hydrologic cycle. Brought to Earth's surface through volcanic eruptions.
  25. 25. 64 K Kelp Kelps are large seaweeds (algae) belonging to the brown algae(Phaeophyceae) in the order Laminariales. There are about 30 differentgenera. Kelp grows in underwater "forests" (kelp forests) in shallow oceans, and is thought to have appeared in the Miocene, 23 to 5 million years ago. The organisms require nutrient-rich water with temperatures between 6 and 14 °C (43 and 57 °F). They are known for their high growth rate — the generaMacrocystis and Nereocystis can grow as fast as half a metre a day, ultimately reaching 30 to 80 metres (100 to 260 ft).
  26. 26. Through the 19th century, the word "kelp" was closely associated with seaweeds that could be burned to obtain soda ash (primarily sodium carbonate). The seaweeds used included species from both the orders Laminariales and Fucales. The word "kelp" was also used directly to refer to these processed ashes. Ketone A ketone (alkanone) /ːkiːtoʊn/ is an organic compound with the structure RC(=O)R', where R and R' can be a variety of carbon- containing substituents. Ketones feature a carbonyl group (C=O) bonded to two other carbon atoms. Many ketones are known and 65 many are of great importance in industry and in biology. Examples include many sugars (ketoses) and the industrial solvent acetone. Nomenclature and etymology The word ketone derives its name from Aketon, an old German word for acetone. According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -ane of the parent alkane to -anone. For the most important ketones, however, traditional nonsystematic names are still generally used, for example acetone and benzophenone. These nonsystematic names are considered retained IUPAC names, although some introductory chemistry textbooks use names such as 2-propanone or propan-2-one instead of acetone, the simplest ketone (C H3-CO-CH3). The position of the carbonyl group is usually denoted by a number. Although used infrequently, oxo is the IUPAC nomenclature for a ketone functional group. Other prefixes, however, are also used. For some common chemicals (mainly in biochemistry), keto or oxo refer to the ketone functional group. The term oxo is used widely through chemistry. For example, it also refers to an oxygen atom bonded to a transition metal (a metal oxo).
  27. 27. Classes of ketones Ketones are classified on the basis of their substituents. One broad classification subdivides ketones into symmetrical and asymmetrical derivatives, depending on the equivalency of the two organic substituents attached to the carbonyl center. Acetone and benzophenone (C6H5C(O)C6H5) are symmetrical ketones. Acetophenone (C6H5C(O)CH3) is an asymmetrical ketone. In the area of stereochemistry, asymmetrical ketones are known for being prochiral. Diketones Many kinds of diketones are known, some with unusual properties. 66 The simplest is diacetyl (CH3C(O)C(O)CH3), once used as butter- flavoring in popcorn. Acetylacetone (pentane-2,4-dione) is virtually a misnomer (inappropriate name) because this species exists mainly as the monoenol CH3C(O)CH=C(OH)CH3. Its enolate is a common ligand in coordination chemistry. Unsaturated ketones Ketones containing alkene and alkyne units are often called unsaturated ketones. The most widely used member of this class of compounds is methyl vinyl ketone, CH3C(O)CH=CH2, which is useful in the Robinson annulation reaction. Lest there be confusion, a ketone itself is a site of unsaturation; that is, it can be hydrogenated. Cyclic ketones Many ketones are cyclic. The simplest class have the formula (CH2)nCO, where n varies from 3 for cyclopropanone to the teens. Larger derivatives exist. Cyclohexanone, a symmetrical cyclic ketone, is an important intermediate in the production of nylon. Isophorone, derived from acetone, is an unsaturated, asymmetrical ketone that is the precursor to other polymers. Muscone, 3-methylpentadecanone, is an animal pheromone. Another cyclic ketone is cyclobutanone, having the formula C4H6O.
  28. 28. Kinetics The cars of a roller coaster reach their maximum kinetic energy when at the bottom of their path. When they start rising, the kinetic energy begins to be converted to gravitational potential energy. The sum of kinetic and potential energy in the system remains constant, ignoring losses to friction. Common symbol(s): KE, Ek, or T SI unit: joule (J) Derivations from other quantities: Ek = ½mv2 Ek = Et+Er The kinetic energy of an object is the energy which it possesses due to its motion.[1] It is defined as the work needed to 67 accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body in decelerating from its current speed to a state of rest. In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is ½ mv². In relativistic mechanics, this is only a good approximation when v is much less than the speed of light. K- Potassium Potassium is a chemical element with symbol K (from Neo-Latin kalium) and atomic number 19. Elemental potassium is a soft silvery- white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction and burning with a lilac flame.
  29. 29. Naturally occurring potassium is composed of three isotopes, one of which, 40K, is radioactive. Traces (0.012%) of this isotope are found in all potassium making it the most common radioactive element in the human body and in many biological materials, as well as in common building materials such as concrete. Potassium ions are necessary for the function of all living cells. Potassium ion diffusion is a key mechanism in nerve transmission, and potassium depletion in animals, including humans, results in various cardiac dysfunctions. Potassium accumulates in plant cells, and thus fresh fruits and vegetables are a good dietary source of it. This resulted in potassium first being isolated from potash, the ashes of plants, giving the element its name. For the same reason, heavy crop production rapidly depletes soils of potassium, and agricultural fertilizers consume 95% of global potassium chemical production. 68 Krypton Krypton (from Greek: κρσπτός kryptos "the hidden one") is a chemical element with symbol Kr and atomic number 36. It is a member of group 18 (noble gases) elements. A colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other rare gases in fluorescent lamps. Krypton is inert for most practical purposes. Krypton, like the other noble gases, can be used in lighting and photography. Krypton light has a large number of spectral lines, and krypton's high light output in plasmas allows it to play an important role in many high-powered gas lasers (krypton ion and excimer lasers), which pick out one of the many spectral lines to amplify. There is also a specific krypton fluoride laser. The high power and relative ease of operation of krypton discharge tubes caused (from 1960 to 1983) the official length of a meter to be defined in terms of the wavelength of the 605 nm (orange) spectral line of krypton-86
  30. 30. Krypton is characterized by several sharp emission lines (spectral signatures) the strongest being green and yellow.[9] It is one of the products of uranium fission.[10] Solidified krypton is white and crystalline with a face-centered cubic crystal structure, which is a common property of all noble gases (except helium, with a hexagonal close-packed crystal structure) 69
  31. 31. L Leeuwenhoek, Anton Van Leeuwenhoek, Anton Van (1632-1723), Dutch microscopist and biologist whose improvements on the light microscope enabled him and other biologist to make many important discoveries. Leeuwenhoek was born in Delft, Netherlands, on October 24, 1632. His early schooling was brief and at the age of 16 he was apprenticed to a cloth merchant and soon after became shop booker and cashier. As a hobby, Leeuwenhoek began grinding lenses and using them to study minute objects, particularly small organisms. The hobby soon became a major activity that eventually led to many remarkable accomplishments. Leeuwenhoek used single, small, double convex lenses with very short focus. The lenses where mounted in flat metal plates equipped with handles so that the instruments could be held close to the eye. Firm objects were attached to a pin mounted behind the lens and fluids were placed on glass in the same position. A screw adjustment provided for positioning and focusing. By adjusting the lighting and arranging the background, Leeuwenhoek succeeded in obtaining magnification and particularly in resolving power that exceeded those possible with early compound microscope. In 1668, he extended the Italian anatomist Marcello Malpighi’s demonstration of capillaries in the circulatory system. He also observed the circulation of red blood corpuscles
  32. 32. 70 in several capillary systems, including those in the tail of an eel, the web of a frog foot and the ear of a rabbit. In 1674 he described red blood corpuscles in many other animals. In 1667, Leeuwenhoek described the spermatozoa of the dog, rabbit, fish, man, and several other animals. He held the philosophic position of a preformationist, specifically an animalculist –that is, he believed that the entire form of an adult in miniature was present in the sperm and merely unfolded and grew during the embryonic period. Among some of the other subjects that Leeuwenhoek studied with his microscope were muscle fibers, hairs, and epidermal (skin) cells, the nerves of various animals, ciliated protozoa, rotifers, plant tissues and the anatomy of insects. Leeuwenhoek also described the three morphological types of bacteria: bacillus, cocci, and spirilla; measured the quantity of perspiration; and demonstrated that blood did not ferment in the body. In 1680, Leeuwenhoek became a fellow of the Royal Society and in 1699 a correspondent of the Academie des Sciences in Paris. He died in Delft on August 26, 1723. Lenses For centuries, human beings have been able to do some pretty remarkable things with lenses. Although we can’t be sure when or how the first person stumbled onto the concept, it is clear that at some point in the past, ancient people (probably from the Near East) realized that they could manipulate light using a shaped piece of glass. Over the centuries, how and for what purpose lenses were used began to increase, as people discovered that they could accomplish different things using differently shaped lenses. In addition to making distant objects appear nearer (i.e. the telescope), they could also be used to make small objects appear larger and blurry objects appear clear (i.e. magnifying glasses and corrective lenses). The lenses used to accomplish these tasks fall into two categories of simple lenses: Convex and Concave Lenses.
  33. 33. 71 A concave lens is a lens that possesses at least one surface that curves inwards. It is a diverging lens, meaning that it spreads out light rays that have been refracted through it. A concave lens is thinner at its centre than at its edges, and is used to correct short- sightedness (myopia). The writings of Pliny the Elder (23–79) makes mention of what is arguably the earliest use of a corrective lens. According to Pliny, Emperor Nero was said to watch gladiatorial games using an emerald, presumably concave shaped to correct for myopia. After light rays have passed through the lens, they appear to come from a point called the principal focus. This is the point onto which the collimated light that moves parallel to the axis of the lens is focused. The image formed by a concave lens is virtual, meaning that it will appear to be farther away than it actually is, and therefore smaller than the object itself. Curved mirrors often have this effect, which is why many (especially on cars) come with a warning: Objects in mirror are closer than they appear. The image will also be upright, meaning not inverted, as some curved reflective surfaces and lenses have been known to do. As every child is sure to find out at some point in their life, lenses can be an endless source of fun. They can be used for everything from examining small objects and type to focusing the sun’s rays. In the latter case, hopefully they choose to be humanitarian and burn things like paper and grass rather than ants! But the fact remains, a Convex Lens is the source of this scientific marvel. Typically made of glass or transparent plastic, a convex lens has at least one surface that curves outward like the exterior of a sphere. Of all lenses, it is the most common given its many uses.
  34. 34. 72 A convex lens is also known as a converging lens. A converging lens is a lens that converges rays of light that are travelling parallel to its principal axis. They can be identified by their shape which is relatively thick across the middle and thin at the upper and lower edges. The edges are curved outward rather than inward. As light approaches the lens, the rays are parallel. As each ray reaches the glass surface, it refracts according to the effective angle of incidence at that point of the lens. Since the surface is curved, different rays of light will refract to different degrees; the outermost rays will refract the most. This runs contrary to what occurs when a divergent lens (otherwise known as concave, biconcave or Plano- concave) is employed. In this case, light is refracted away from the axis and outward. Lenses are classified by the curvature of the two optical surfaces. If the lens is biconvex or Plano-convex, the lens is called positive or converging. Most convex lenses fall into this category. A lens is biconvex (or double convex, or just convex) if both surfaces are convex. These types of lenses are used in the manufacture of magnifying glasses. If both surfaces have the same radius of curvature, the lens is known as an equiconvex biconvex. If one of the surfaces is flat, the lens is plano- convex (or plano-concave depending on the curvature of the other surface). A lens with one convex and one concave side is convex- concave or meniscus. These lenses are used in the manufacture of corrective lenses. Lewis, Gilbert Newton Gilbert Newton Lewis Formers( October 23, 1875 – March 23, 1946) was an American physical chemist known for the discovery of the covalent bond and his concept of electron pairs; his Lewis dot structures and other contributions to valence bond theory have shaped modern theories of chemical bonding. Lewis has successfully contributed
  35. 35. 73 to thermodynamics, photochemistry, and isotope separation, and is also known for his concept of acids and bases. G. N. Lewis was born in 1875 in Weymouth, Massachusetts. After receiving his PhD in chemistry from Harvard University and studying abroad in Germany and the Philippines, Lewis moved to California to teach chemistry at the University of California, Berkeley. Several years later, he became the Dean of the college of Chemistry at Berkeley, where he spent the rest of his life. As a professor, he incorporated thermodynamic principles into the chemistry curriculum and reformed chemical thermodynamics in a mathematically rigorous manner accessible to ordinary chemists. He began measuring the free energy values related to several chemical processes, both organic and inorganic. In 1916, he also proposed his theory of bonding and added information about electrons in the periodic table of the elements. In 1933, he started his research on isotope separation. Lewis worked with hydrogen and managed to purify a sample of heavy water. He then came up with his theory of acids and bases, and did work in photochemistry during the last years of his life. In 1926, Lewis coined the term "photon" for the smallest unit of radiant energy. He was a brother in Alpha Chi Sigma, the professional chemistry fraternity. Though he was nominated 35 times, G. N. Lewis never won the Nobel Prize in Chemistry. On March 23, 1946, Lewis was found dead in his Berkeley laboratory where he had been working with hydrogen cyanide; many postulated that the cause of his death was suicide. After Lewis' death, his children followed their father's career in chemistry. Most of Lewis’ lasting interests originated during his Harvard years. The most important was thermodynamics, a subject in which Richards was very active at that time. Although most of the important thermodynamic relations were known by 1895, they were seen as isolated equations, and had not yet been rationalized as a logical system, from which, given one relation, the rest could be derived. Moreover, these relations were inexact, applying only to ideal chemical systems. These were two outstanding problems of theoretical thermodynamics. In two long and ambitious theoretical papers in 1900 and 1901, Lewis tried to provide a solution. Lewis introduced the thermodynamic concept of activity and coined the term "fugacity".[5] His new idea of fugacity, or "escaping tendency", was a function with the dimensions of pressure which expressed the tendency of a 74
  36. 36. substance to pass from one chemical phase to another. Lewis believed that fugacity was the fundamental principle from which a system of real thermodynamic relations could be derived. This hope was not realized, though fugacity did find a lasting place in the description of real gases. Lewis’ early papers also reveal an unusually advanced awareness of J. W. Gibbs’s and P. Duhem’s ideas of free energy and thermodynamic potential. These ideas were well known to physicists and mathematicians, but not to most practical chemists, who regarded them as abstruse and inapplicable to chemical systems. Most chemists relied on the familiar thermodynamics of heat (enthalpy) of Berthelot, Ostwald, and Van’s Hoff, and the calorimetric school. Heat of reaction is not, of course, a measure of the tendency of chemical changes to occur, and Lewis realized that only free energy and entropy could provide an exact chemical thermodynamics. He derived free energy from fugacity; he tried, without success, to obtain an exact expression for the entropy function, which in 1901 had not been defined at low temperatures. Richards too tried and failed, and not until Nernst succeeded in 1907 was it possible to calculate entropies unambiguously. Although Lewis’ fugacity- based system did not last, his early interest in free energy and entropy proved most fruitful, and much of his career was devoted to making these useful concepts accessible to practical chemists. At Harvard, Lewis also wrote a theoretical paper on the thermodynamics of blackbody radiation in which he postulated that light has a pressure. He later revealed that he had been discouraged from pursuing this idea by his older, more conservative colleagues, who were unaware that W. Wien and others were successfully pursuing the same line of thought. Lewis’ paper remained unpublished; but his interest in radiation and quantum theory, and (later) in relativity, sprang from this early, aborted effort. From the start of his career, Lewis regarded himself as both chemist and physicist. Litmus Litmus, mixture of coloured organic compounds obtained from several species of lichens that 75
  37. 37. grow in the Netherlands, particularly Lecanora tartarea and Roccella tinctorum. Litmus turns red in acidic solutions and blue in alkaline solutions and is the oldest and most commonly used indicator of whether a substance is an acid or a base. Treatment of the lichens with ammonia, potash, and lime in the presence of air produces the various coloured components of litmus. By 1840 litmus had been partially separated into several substances named azolitmin, erythrolitmin, spaniolitmin, and erythrolein. These are apparently mixtures of closely related compounds that were identified. Logic gate A logic gate is an idealized or physical device implementing a Boolean function, that is, it performs a logical operation on one or more logical inputs, and produces a single logical output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and unlimited fan-out, or it may refer to a non-ideal physical device[1] (see Ideal and real op-amps for comparison). Logic gates are primarily implemented using diodes or transistors acting as electronic switches, but can also be constructed using electromagnetic relays (relay logic), fluidic logic, pneumatic logic, optics, molecules, or even mechanical elements. With amplification, logic gates can be cascaded in the same way that Boolean functions can be composed, allowing the construction of a physical model of all of Boolean logic, and therefore, all of the algorithms and mathematics that can be described with Boolean logic. Logic circuits include such devices as multiplexers, registers, arithmetic logic units (ALUs), and computer memory, all the way up through complete microprocessors, which may contain more than 100 million gates. 76
  38. 38. INDEX G Gamma rays, 41-42 Geiger, Hans Wilhelm, 42-43 Giaunghe, William France, 43-44 Gummite, p.44 Gyroscope, p.45 H Heart, pp.46-47 Heat energy, p.48 Hemoglobin, pp.48- 50 Hydroelectricity, pp.50-51 Hydrogen bond, pp.51-52 I Ionic bond, pp.53- 54 Insulin, pp.54-56 Iron, pp.56-57 Isomer, pp.58-60 Isomerization, p.60 J Jade, p.61 Jadeite, pp.61-62 Jasper, 62 Jolly balance, p.63 Juvenile water, pp.63-64 K Kelp, p.65 Ketone, pp.65-67 Kinetics, pp.67-68 K-potassium, p.68 Krypton, p.69 L Leeuwenhoek, Anton Van, pp.70-71 Lenses, pp.71-73 Lewis, Gilbert, pp.73-75 Litmus, pp.75-76 Logic gate, p.76