1.
Ferrocerium
–
Ferrocerium is a synthetic pyrophoric alloy that produces hot sparks that can reach temperatures of 3,000 °C when rapidly oxidized by the process of striking. Due to ferroceriums ability to ignite in adverse conditions, rods of ferrocerium are commonly used as a combustion device in survival kits. Invented by 1903 by the Austrian chemist Carl Auer von Welsbach, the pyrophoric effect is dependent on the brittleness of the alloy and its low autoignition temperature. e. The sparks are tiny pieces of burning metal, the sparking is due to ceriums low ignition temperature of between 150 and 180 °C. About 700 tons were produced in 2000, modern flint bears no chemical relationship to the mineral flint, the name for two types of rock historically used to generate sparks. A flint spark lighter is a type of lighter used in applications to safely light a gaseous fuel to start a flame. It is most commonly used for bunsen burners and oxyacetylene welding torches and this manual rubbing action, done by squeezing the handle, creates a spark which then lights the gaseous fuel. As tinder-igniting campfire starter rods it is sold under trade names as Blastmatch, Fire Steel and Metal-Match for survivalists. Some manufacturers and resellers incorrectly call them magnesium rods, the sparks from the ferrocerium will ignite the magnesium, which will in turn ignite the tinder. It is also known in Europe as Auermetall after its inventor Baron Carl Auer von Welsbach, three different Auermetalls were developed, the first was iron and cerium, the second also included lanthanum to produce brighter sparks, and the third added other heavy metals. In the Baron von Welsbachs first alloy, 30% iron was added to purified cerium, iron reacts with rare earth metals to form hard intermetallic compounds similar to those in neodymium magnets, such magnets are known to generate sparks when broken. A modern ferrocerium firesteel product is composed of an alloy of rare earth metals called mischmetal, plus iron, a variety of other components are added to modify the spark and processing characteristics. Most contemporary flints are hardened with 20% iron oxide and 2% magnesium oxide, firelighting Jorgenson, John D. Corathers, Lisa A. Gambogi, Joseph, Kuck, Peter H. Magyar, Michael J. Papp, John F. Shedd, Kim B
2.
Bunsen burner
–
A Bunsen burner, named after Robert Bunsen, is a common piece of laboratory equipment that produces a single open gas flame, which is used for heating, sterilization, and combustion. The gas can be gas or a liquefied petroleum gas, such as propane, butane. In 1852 the University of Heidelberg hired Bunsen and promised him a new laboratory building, the city of Heidelberg had begun to install coal-gas street lighting, and so the university laid gas lines to the new laboratory. The designers of the building intended to use the gas not just for illumination, for any burner lamp, it was desirable to maximize the temperature and minimize luminosity. However, existing laboratory burner lamps left much to be desired not just in terms of the heat of the flame, but also regarding economy and simplicity. While the building was still under construction in late 1854 Bunsen suggested certain design principles to the mechanic, Peter Desaga. The Bunsen/Desaga design succeeded in generating a hot, sootless, non-luminous flame by mixing the gas with air in a controlled fashion before combustion, Desaga created adjustable slits for air at the bottom of the cylindrical burner, with the flame igniting at the top. By the time the building opened early in 1855 Desaga had made fifty of the burners for Bunsens students, two years later Bunsen published a description, and many of his colleagues soon adopted the design. Bunsen burners are now used in all around the world. The device in use today safely burns a continuous stream of a gas such as natural gas or a liquefied petroleum gas such as propane, butane. The hose barb is connected to a gas nozzle on the bench with rubber tubing. Most laboratory benches are equipped with multiple gas nozzles connected to a gas source, as well as vacuum, nitrogen. The gas then flows up through the base through a hole at the bottom of the barrel and is directed upward. There are open slots in the side of the bottom to admit air into the stream via the venturi effect. The most common methods of lighting the burner are using a match or a spark lighter, the amount of air mixed with the gas stream affects the completeness of the combustion reaction. Less air yields an incomplete and thus cooler reaction, while a gas stream well mixed with air provides oxygen in an amount and thus a complete. The air flow can be controlled by opening or closing the openings at the base of the barrel. If the collar at the bottom of the tube is adjusted so more air can mix with the gas before combustion, the flame will burn hotter, appearing blue as a result
3.
Chemistry
–
Chemistry is a branch of physical science that studies the composition, structure, properties and change of matter. Chemistry is sometimes called the science because it bridges other natural sciences, including physics. For the differences between chemistry and physics see comparison of chemistry and physics, the history of chemistry can be traced to alchemy, which had been practiced for several millennia in various parts of the world. The word chemistry comes from alchemy, which referred to a set of practices that encompassed elements of chemistry, metallurgy, philosophy, astrology, astronomy, mysticism. An alchemist was called a chemist in popular speech, and later the suffix -ry was added to this to describe the art of the chemist as chemistry, the modern word alchemy in turn is derived from the Arabic word al-kīmīā. In origin, the term is borrowed from the Greek χημία or χημεία and this may have Egyptian origins since al-kīmīā is derived from the Greek χημία, which is in turn derived from the word Chemi or Kimi, which is the ancient name of Egypt in Egyptian. Alternately, al-kīmīā may derive from χημεία, meaning cast together, in retrospect, the definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. The term chymistry, in the view of noted scientist Robert Boyle in 1661, in 1837, Jean-Baptiste Dumas considered the word chemistry to refer to the science concerned with the laws and effects of molecular forces. More recently, in 1998, Professor Raymond Chang broadened the definition of chemistry to mean the study of matter, early civilizations, such as the Egyptians Babylonians, Indians amassed practical knowledge concerning the arts of metallurgy, pottery and dyes, but didnt develop a systematic theory. Greek atomism dates back to 440 BC, arising in works by such as Democritus and Epicurus. In 50 BC, the Roman philosopher Lucretius expanded upon the theory in his book De rerum natura, unlike modern concepts of science, Greek atomism was purely philosophical in nature, with little concern for empirical observations and no concern for chemical experiments. Work, particularly the development of distillation, continued in the early Byzantine period with the most famous practitioner being the 4th century Greek-Egyptian Zosimos of Panopolis. He formulated Boyles law, rejected the four elements and proposed a mechanistic alternative of atoms. Before his work, though, many important discoveries had been made, the Scottish chemist Joseph Black and the Dutchman J. B. English scientist John Dalton proposed the theory of atoms, that all substances are composed of indivisible atoms of matter. Davy discovered nine new elements including the alkali metals by extracting them from their oxides with electric current, british William Prout first proposed ordering all the elements by their atomic weight as all atoms had a weight that was an exact multiple of the atomic weight of hydrogen. The inert gases, later called the noble gases were discovered by William Ramsay in collaboration with Lord Rayleigh at the end of the century, thereby filling in the basic structure of the table. Organic chemistry was developed by Justus von Liebig and others, following Friedrich Wöhlers synthesis of urea which proved that organisms were, in theory
4.
Physics
–
Physics is the natural science that involves the study of matter and its motion and behavior through space and time, along with related concepts such as energy and force. One of the most fundamental disciplines, the main goal of physics is to understand how the universe behaves. Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy, Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the mechanisms of other sciences while opening new avenues of research in areas such as mathematics. Physics also makes significant contributions through advances in new technologies that arise from theoretical breakthroughs, the United Nations named 2005 the World Year of Physics. Astronomy is the oldest of the natural sciences, the stars and planets were often a target of worship, believed to represent their gods. While the explanations for these phenomena were often unscientific and lacking in evidence, according to Asger Aaboe, the origins of Western astronomy can be found in Mesopotamia, and all Western efforts in the exact sciences are descended from late Babylonian astronomy. The most notable innovations were in the field of optics and vision, which came from the works of many scientists like Ibn Sahl, Al-Kindi, Ibn al-Haytham, Al-Farisi and Avicenna. The most notable work was The Book of Optics, written by Ibn Al-Haitham, in which he was not only the first to disprove the ancient Greek idea about vision, but also came up with a new theory. In the book, he was also the first to study the phenomenon of the pinhole camera, many later European scholars and fellow polymaths, from Robert Grosseteste and Leonardo da Vinci to René Descartes, Johannes Kepler and Isaac Newton, were in his debt. Indeed, the influence of Ibn al-Haythams Optics ranks alongside that of Newtons work of the same title, the translation of The Book of Optics had a huge impact on Europe. From it, later European scholars were able to build the devices as what Ibn al-Haytham did. From this, such important things as eyeglasses, magnifying glasses, telescopes, Physics became a separate science when early modern Europeans used experimental and quantitative methods to discover what are now considered to be the laws of physics. Newton also developed calculus, the study of change, which provided new mathematical methods for solving physical problems. The discovery of new laws in thermodynamics, chemistry, and electromagnetics resulted from greater research efforts during the Industrial Revolution as energy needs increased, however, inaccuracies in classical mechanics for very small objects and very high velocities led to the development of modern physics in the 20th century. Modern physics began in the early 20th century with the work of Max Planck in quantum theory, both of these theories came about due to inaccuracies in classical mechanics in certain situations. Quantum mechanics would come to be pioneered by Werner Heisenberg, Erwin Schrödinger, from this early work, and work in related fields, the Standard Model of particle physics was derived. Areas of mathematics in general are important to this field, such as the study of probabilities, in many ways, physics stems from ancient Greek philosophy
5.
Chemical reaction
–
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Nuclear chemistry is a sub-discipline of chemistry that involves the reactions of unstable. The substance initially involved in a reaction are called reactants or reagents. Chemical reactions are characterized by a chemical change, and they yield one or more products. Reactions often consist of a sequence of individual sub-steps, the elementary reactions. Chemical reactions are described with chemical equations, which present the starting materials, end products. Chemical reactions happen at a characteristic reaction rate at a given temperature, typically, reaction rates increase with increasing temperature because there is more thermal energy available to reach the activation energy necessary for breaking bonds between atoms. Reactions may proceed in the forward or reverse direction until they go to completion or reach equilibrium, Reactions that proceed in the forward direction to approach equilibrium are often described as spontaneous, requiring no input of free energy to go forward. Non-spontaneous reactions require input of energy to go forward. Different chemical reactions are used in combinations during chemical synthesis in order to obtain a desired product, in biochemistry, a consecutive series of chemical reactions form metabolic pathways. These reactions are catalyzed by protein enzymes. Chemical reactions such as combustion in fire, fermentation and the reduction of ores to metals were known since antiquity, in the Middle Ages, chemical transformations were studied by Alchemists. They attempted, in particular, to lead into gold, for which purpose they used reactions of lead. The process involved heating of sulfate and nitrate minerals such as sulfate, alum. In the 17th century, Johann Rudolph Glauber produced hydrochloric acid and sodium sulfate by reacting sulfuric acid, further optimization of sulfuric acid technology resulted in the contact process in the 1880s, and the Haber process was developed in 1909–1910 for ammonia synthesis. From the 16th century, researchers including Jan Baptist van Helmont, Robert Boyle, the phlogiston theory was proposed in 1667 by Johann Joachim Becher. It postulated the existence of an element called phlogiston, which was contained within combustible bodies. This proved to be false in 1785 by Antoine Lavoisier who found the explanation of the combustion as reaction with oxygen from the air
6.
Nuclear reaction
–
Thus, a nuclear reaction must cause a transformation of at least one nuclide to another. Nuclear reaction is a term implying a change in a nuclide. Natural nuclear reactions occur in the interaction between rays and matter, and nuclear reactions can be employed artificially to obtain nuclear energy, at an adjustable rate. The complete equation therefore reads, or more simply, Instead of using the equations in the style above. This style of the form AD is equivalent to A + b producing c + D, the reaction above would be written as Li-6α. In 1919, Ernest Rutherford was able to accomplish transmutation of nitrogen into oxygen at the University of Manchester and this was the first observation of an induced nuclear reaction, that is, a reaction in which particles from one decay are used to transform another atomic nucleus. Kinetic energy may be released during the course of a reaction or kinetic energy may have to be supplied for the reaction to take place, in a nuclear reaction, the total energy is conserved. The missing rest mass must therefore reappear as kinetic energy released in the reaction, using Einsteins mass-energy equivalence formula E = mc², the amount of energy released can be determined. We first need the energy equivalent of one atomic unit,1 u c² = × ² =1.49242 × 10−10 kg ² =1.49242 × 10−10 J × =931.49 MeV. Hence, the energy released is 0.0238 ×931 MeV =22.2 MeV, expressed differently, the mass is reduced by 0. 3%, corresponding to 0. 3% of 90 PJ/kg is 270 TJ/kg. Consequently, alpha particles appear frequently on the hand side of nuclear reactions. When the product nucleus is metastable, this is indicated by placing an asterisk next to its atomic number and this energy is eventually released through nuclear decay. A small amount of energy may also emerge in the form of X-rays, generally, the product nucleus has a different atomic number, and thus the configuration of its electron shells is wrong. As the electrons rearrange themselves and drop to lower energy levels, for the particular case discussed above, the reaction energy has already been calculated as Q =22.2 MeV. Hence, The reaction energy is positive for exothermal reactions and negative for endothermal reactions, on the one hand, it is the difference between the sums of kinetic energies on the final side and on the initial side. But on the hand, it is also the difference between the nuclear rest masses on the initial side and on the final side. If the reaction equation is balanced, that not mean that the reaction really occurs. The rate at which reactions occur depends on the energy, the particle flux
7.
Joules
–
The joule, symbol J, is a derived unit of energy in the International System of Units. It is equal to the transferred to an object when a force of one newton acts on that object in the direction of its motion through a distance of one metre. It is also the energy dissipated as heat when a current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule, one joule can also be defined as, The work required to move an electric charge of one coulomb through an electrical potential difference of one volt, or one coulomb volt. This relationship can be used to define the volt, the work required to produce one watt of power for one second, or one watt second. This relationship can be used to define the watt and this SI unit is named after James Prescott Joule. As with every International System of Units unit named for a person, note that degree Celsius conforms to this rule because the d is lowercase. — Based on The International System of Units, section 5.2. The CGPM has given the unit of energy the name Joule, the use of newton metres for torque and joules for energy is helpful to avoid misunderstandings and miscommunications. The distinction may be also in the fact that energy is a scalar – the dot product of a vector force. By contrast, torque is a vector – the cross product of a distance vector, torque and energy are related to one another by the equation E = τ θ, where E is energy, τ is torque, and θ is the angle swept. Since radians are dimensionless, it follows that torque and energy have the same dimensions, one joule in everyday life represents approximately, The energy required to lift a medium-size tomato 1 m vertically from the surface of the Earth. The energy released when that same tomato falls back down to the ground, the energy required to accelerate a 1 kg mass at 1 m·s−2 through a 1 m distance in space. The heat required to raise the temperature of 1 g of water by 0.24 °C, the typical energy released as heat by a person at rest every 1/60 s. The kinetic energy of a 50 kg human moving very slowly, the kinetic energy of a 56 g tennis ball moving at 6 m/s. The kinetic energy of an object with mass 1 kg moving at √2 ≈1.4 m/s, the amount of electricity required to light a 1 W LED for 1 s. Since the joule is also a watt-second and the unit for electricity sales to homes is the kW·h. For additional examples, see, Orders of magnitude The zeptojoule is equal to one sextillionth of one joule,160 zeptojoules is equivalent to one electronvolt. The nanojoule is equal to one billionth of one joule, one nanojoule is about 1/160 of the kinetic energy of a flying mosquito
8.
Rectangular potential barrier
–
In quantum mechanics, the rectangular potential barrier is a standard one-dimensional problem that demonstrates the phenomena of wave-mechanical tunneling and wave-mechanical reflection. The problem consists of solving the one-dimensional time-independent Schrödinger equation for a particle encountering a rectangular potential energy barrier and it is usually assumed, as here, that a free particle impinges on the barrier from the left. In classical wave-physics, this effect is known as evanescent wave coupling, the likelihood that the particle will pass through the barrier is given by the transmission coefficient, whereas the likelihood that it is reflected is given by the reflection coefficient. Schrödingers wave-equation allows these coefficients to be calculated, Θ =0, x <0, Θ =1, x >0 is the Heaviside step function. The barrier is positioned between x =0 and x = a, the barrier can be shifted to any x position without changing the results. The first term in the Hamiltonian, − ℏ22 m d 2 d x 2 ψ is the kinetic energy, the barrier divides the space in three parts. The index r/l on the coefficients A and B denotes the direction of the velocity vector, note that, if the energy of the particle is below the barrier height, k 1 becomes imaginary and the wave function is exponentially decaying within the barrier. Nevertheless, we keep the notation r/l even though the waves are not propagating anymore in this case, the case E = V0 is treated below. The coefficients A, B, C have to be found from the conditions of the wave function at x =0 and x = a. The wave function and its derivative have to be continuous everywhere, ψ L = ψ C d d x ψ L = d d x ψ C ψ C = ψ R d d x ψ C = d d x ψ R. The complete solution of the Schrödinger equation is found in the way as above by matching wave functions. At this point, it is instructive to compare the situation to the classical case, in both cases, the particle behaves as a free particle outside of the barrier region. A classical particle with energy E larger than the barrier height V0 would always pass the barrier, to study the quantum case, consider the following situation, a particle incident on the barrier from the left side. It may be reflected or transmitted, to find the amplitudes for reflection and transmission for incidence from the left, we put in the above equations A r =1, A l = r, C l =0, and C r = t. We then eliminate the coefficients B l, B r from the equation and solve for r and t. The result is, t =4 k 0 k 1 e − i a 2 − e 2 i a k 12 r = sin 2 i k 0 k 1 cos + sin . Due to the symmetry of the model, the amplitudes for incidence from the right are the same as those from the left. Note that these expressions hold for any energy E >0 and this effect, which differs from the classical case, is called quantum tunneling
9.
Maxima and minima
–
Pierre de Fermat was one of the first mathematicians to propose a general technique, adequality, for finding the maxima and minima of functions. As defined in set theory, the maximum and minimum of a set are the greatest and least elements in the set, unbounded infinite sets, such as the set of real numbers, have no minimum or maximum. The value of the function at a point is called the maximum value of the function. Similarly, the function has a minimum point at x∗ if f ≤ f for all x in X within distance ε of x∗. A similar definition can be used when X is a space, since the definition just given can be rephrased in terms of neighbourhoods. Note that a maximum point is always a local maximum point. In both the global and local cases, the concept of a strict extremum can be defined, note that a point is a strict global maximum point if and only if it is the unique global maximum point, and similarly for minimum points. A continuous real-valued function with a compact domain always has a maximum point, an important example is a function whose domain is a closed interval of real numbers. Finding global maxima and minima is the goal of mathematical optimization, if a function is continuous on a closed interval, then by the extreme value theorem global maxima and minima exist. Furthermore, a global maximum either must be a maximum in the interior of the domain. So a method of finding a maximum is to look at all the local maxima in the interior, and also look at the maxima of the points on the boundary. Local extrema of functions can be found by Fermats theorem. For any function that is defined piecewise, one finds a maximum by finding the maximum of each piece separately, the function x2 has a unique global minimum at x =0. The function x3 has no global minima or maxima, although the first derivative is 0 at x =0, this is an inflection point. The function x x has a global maximum at x = e. The function x−x has a global maximum over the positive real numbers at x = 1/e. The function x3/3 − x has first derivative x2 −1, setting the first derivative to 0 and solving for x gives stationary points at −1 and +1. From the sign of the second derivative we can see that −1 is a local maximum, note that this function has no global maximum or minimum
10.
Potential energy
–
In physics, potential energy is energy possessed by a body by virtue of its position relative to others, stresses within itself, electric charge, and other factors. The unit for energy in the International System of Units is the joule, the term potential energy was introduced by the 19th century Scottish engineer and physicist William Rankine, although it has links to Greek philosopher Aristotles concept of potentiality. Potential energy is associated with forces that act on a body in a way that the work done by these forces on the body depends only on the initial and final positions of the body in space. These forces, that are called potential forces, can be represented at every point in space by vectors expressed as gradients of a scalar function called potential. Potential energy is the energy of an object. It is the energy by virtue of a position relative to other objects. Potential energy is associated with restoring forces such as a spring or the force of gravity. The action of stretching the spring or lifting the mass is performed by a force that works against the force field of the potential. This work is stored in the field, which is said to be stored as potential energy. If the external force is removed the field acts on the body to perform the work as it moves the body back to the initial position. Suppose a ball which mass is m, and it is in h position in height, if the acceleration of free fall is g, the weight of the ball is mg. There are various types of energy, each associated with a particular type of force. Chemical potential energy, such as the energy stored in fossil fuels, is the work of the Coulomb force during rearrangement of mutual positions of electrons and nuclei in atoms and molecules. Thermal energy usually has two components, the energy of random motions of particles and the potential energy of their mutual positions. Forces derivable from a potential are also called conservative forces, the work done by a conservative force is W = − Δ U where Δ U is the change in the potential energy associated with the force. The negative sign provides the convention that work done against a force field increases potential energy, common notations for potential energy are U, V, also Ep. Potential energy is closely linked with forces, in this case, the force can be defined as the negative of the vector gradient of the potential field. If the work for a force is independent of the path, then the work done by the force is evaluated at the start
11.
Thermodynamic state
–
Once such a set of values of thermodynamic variables has been specified for a system, the values of all thermodynamic properties of the system are uniquely determined. Usually, by default, a state is taken to be one of thermodynamic equilibrium. This means that the state is not merely the condition of the system at a specific time, Thermodynamics sets up an idealized formalism that can be summarized by a system of postulates of thermodynamics. A thermodynamic system is not simply a physical system, a thermodynamic system is a macroscopic object, the microscopic details of which are not explicitly considered in its thermodynamic description. The number of state variables required to specify the state depends on the system. Always the number is two or more, usually it is not more than some dozen, the choice is usually made on the basis of the walls and surroundings that are relevant for the thermodynamic processes that are to be considered for the system. For Planck, the characteristic of a thermodynamic state of a system that consists of a single phase. Such non-equilibrium identifying state variables indicate that some non-zero flow may be occurring within the system or between system and surroundings and they are uniquely determined by the thermodynamic state as it has been identified by the original state variables. For an idealized continuous or quasi-static process, this means that infinitesimal incremental changes in such variables are exact differentials, together, the incremental changes throughout the process, and the initial and final states, fully determine the idealized process. In the most commonly cited example, an ideal gas. Thus the thermodynamic state would range over a state space. The remaining variable, as well as other such as the internal energy. The state functions satisfy certain constraints, expressed in the laws of thermodynamics. Various thermodynamic diagrams have been developed to model the transitions between thermodynamic states, physical systems found in nature are practically always dynamic and complex, but in many cases, macroscopic physical systems are amenable to description based on proximity to ideal conditions. One such ideal condition is that of an equilibrium state. Such a state is an object of classical or equilibrium thermodynamics. Based on many observations, thermodynamics postulates that all systems that are isolated from the environment will evolve so as to approach unique stable equilibrium states. A few different types of equilibrium are listed below, thermal Equilibrium, When the temperature throughout a system is uniform, the system is in thermal equilibrium
12.
Svante Arrhenius
–
Svante August Arrhenius was a Nobel-Prize winning Swedish scientist, originally a physicist, but often referred to as a chemist, and one of the founders of the science of physical chemistry. He received the Nobel Prize for Chemistry in 1903, becoming the first Swedish Nobel laureate, Arrhenius was born on 19 February 1859 at Vik, near Uppsala, Sweden, the son of Svante Gustav and Carolina Thunberg Arrhenius. His father had been a surveyor for Uppsala University, moving up to a supervisory position. At the age of three, Arrhenius taught himself to read without the encouragement of his parents, and by watching his fathers addition of numbers in his account books, in later life, Arrhenius enjoyed using masses of data to discover mathematical relationships and laws. At age eight, he entered the cathedral school, starting in the fifth grade, distinguishing himself in physics and mathematics. His work focused on the conductivities of electrolytes, in 1884, based on this work, he submitted a 150-page dissertation on electrolytic conductivity to Uppsala for the doctorate. It did not impress the professors, among whom was Cleve, and he received a fourth-class degree, later, extensions of this very work would earn him the 1903 Nobel Prize in Chemistry. Arrhenius put forth 56 theses in his 1884 dissertation, most of which would still be accepted today unchanged or with minor modifications, Arrhenius explanation was that in forming a solution, the salt disassociates into charged particles. Faradays belief had been that ions were produced in the process of electrolysis, Arrhenius proposed that, even in the absence of an electric current and he thus proposed that chemical reactions in solution were reactions between ions. They were far more impressed, and Ostwald even came to Uppsala to persuade Arrhenius to join his research team, Arrhenius declined, however, as he preferred to stay in Sweden for a while and had received an appointment at Uppsala. In an extension of his ionic theory Arrhenius proposed definitions for acids and bases and he believed that acids were substances that produce hydrogen ions in solution and that bases were substances that produce hydroxide ions in solution. The Arrhenius equation gives the basis of the relationship between the activation energy and the rate at which a reaction proceeds. In 1891 he became a lecturer at the Stockholm University College, being promoted to professor of physics in 1895, and rector in 1896. He was married twice, first to his former pupil Sofia Rudbeck, with whom he had one son Olof Arrhenius, about 1900, Arrhenius became involved in setting up the Nobel Institutes and the Nobel Prizes. He was elected a member of the Royal Swedish Academy of Sciences in 1901, for the rest of his life, he would be a member of the Nobel Committee on Physics and a de facto member of the Nobel Committee on Chemistry. He used his positions to arrange prizes for his friends and to attempt to deny them to his enemies, in 1901 Arrhenius was elected to the Swedish Academy of Sciences, against strong opposition. In 1903 he became the first Swede to be awarded the Nobel Prize in chemistry, in 1905, upon the founding of the Nobel Institute for Physical Research at Stockholm, he was appointed rector of the institute, the position where he remained until retirement in 1927. He was elected a Foreign Member of the Royal Society in 1910, in 1911 he won the first Willard Gibbs Award
13.
Arrhenius equation
–
The Arrhenius equation is a formula for the temperature dependence of reaction rates. This equation has a vast and important application in determining rate of chemical reactions, Arrhenius provided a physical justification and interpretation for the formula. Currently, it is best seen as an empirical relationship and it can be used to model the temperature variation of diffusion coefficients, population of crystal vacancies, creep rates, and many other thermally-induced processes/reactions. The Eyring equation, developed in 1935, also expresses the relationship between rate and energy, Arrhenius equation gives the dependence of the rate constant of a chemical reaction on the absolute temperature, a pre-exponential factor and other constants of the reaction. The different units are accounted for in using either the gas constant, R, or the Boltzmann constant, kB, the units of the pre-exponential factor A are identical to those of the rate constant and will vary depending on the order of the reaction. If the reaction is first order it has the units, s−1 and it can be seen that either increasing the temperature or decreasing the activation energy will result in an increase in rate of reaction. Given the small temperature range kinetic studies occur in, it is reasonable to approximate the activation energy as being independent of the temperature. So, when a reaction has a constant that obeys Arrhenius equation. This procedure has become so common in chemical kinetics that practitioners have taken to using it to define the activation energy for a reaction. That is the energy is defined to be times the slope of a plot of ln vs. E a ≡ − R P The modified Arrhenius equation makes explicit the temperature dependence of the pre-exponential factor, the modified equation is usually of the form k = A T n e − E a / The original Arrhenius expression above corresponds to n =0. Fitted rate constants typically lie in the range −1<n<1, theoretical analyses yield various predictions for n. However, if evidence is available, from theory and/or from experiment. Another common modification is the exponential form, k = A exp where β is a dimensionless number of order 1. Arrhenius argued that for reactants to transform into products, they must first acquire an amount of energy. At an absolute temperature T, the fraction of molecules that have an energy greater than Ea can be calculated from statistical mechanics. The concept of energy explains the exponential nature of the relationship. One example comes from the theory of chemical reactions, developed by Max Trautz
14.
Kelvin
–
The kelvin is a unit of measure for temperature based upon an absolute scale. It is one of the seven units in the International System of Units and is assigned the unit symbol K. The kelvin is defined as the fraction 1⁄273.16 of the temperature of the triple point of water. In other words, it is defined such that the point of water is exactly 273.16 K. The Kelvin scale is named after the Belfast-born, Glasgow University engineer and physicist William Lord Kelvin, unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or typeset as a degree. The kelvin is the unit of temperature measurement in the physical sciences, but is often used in conjunction with the Celsius degree. The definition implies that absolute zero is equivalent to −273.15 °C, Kelvin calculated that absolute zero was equivalent to −273 °C on the air thermometers of the time. This absolute scale is known today as the Kelvin thermodynamic temperature scale, when spelled out or spoken, the unit is pluralised using the same grammatical rules as for other SI units such as the volt or ohm. When reference is made to the Kelvin scale, the word kelvin—which is normally a noun—functions adjectivally to modify the noun scale and is capitalized, as with most other SI unit symbols there is a space between the numeric value and the kelvin symbol. Before the 13th CGPM in 1967–1968, the unit kelvin was called a degree and it was distinguished from the other scales with either the adjective suffix Kelvin or with absolute and its symbol was °K. The latter term, which was the official name from 1948 until 1954, was ambiguous since it could also be interpreted as referring to the Rankine scale. Before the 13th CGPM, the form was degrees absolute. The 13th CGPM changed the name to simply kelvin. Its measured value was 7002273160280000000♠0.01028 °C with an uncertainty of 60 µK, the use of SI prefixed forms of the degree Celsius to express a temperature interval has not been widely adopted. In 2005 the CIPM embarked on a program to redefine the kelvin using a more experimentally rigorous methodology, the current definition as of 2016 is unsatisfactory for temperatures below 20 K and above 7003130000000000000♠1300 K. In particular, the committee proposed redefining the kelvin such that Boltzmanns constant takes the exact value 6977138065049999999♠1. 3806505×10−23 J/K, from a scientific point of view, this will link temperature to the rest of SI and result in a stable definition that is independent of any particular substance. From a practical point of view, the redefinition will pass unnoticed, the kelvin is often used in the measure of the colour temperature of light sources. Colour temperature is based upon the principle that a black body radiator emits light whose colour depends on the temperature of the radiator, black bodies with temperatures below about 7003400000000000000♠4000 K appear reddish, whereas those above about 7003750000000000000♠7500 K appear bluish
15.
Cross section (physics)
–
When two particles interact, their mutual cross section is the area transverse to their relative motion within which they must meet in order to scatter from each other. If the particles are spheres that interact only upon contact. If the particles interact through some action-at-a-distance force, such as electromagnetism or gravity, when a cross section is specified as a function of some final-state variable, such as particle angle or energy, it is called a differential cross section. When a cross section is integrated over all scattering angles, it is called a cross section. Cross sections are typically denoted σ and measured in units of area, scattering cross sections may be defined in nuclear and particle physics for collisions of accelerated beams of one type of particle with targets of a second type of particle. The probability for any given reaction to occur is in proportion to its cross section, thus, specifying the cross section for a given reaction is a proxy for stating the probability that a given scattering process will occur. However, these quantities can be factored away, allowing measurement of the underlying two-particle collisional cross section, differential and total scattering cross sections are among the most important measurable quantities in nuclear and particle physics. In a gas of finite-sized particles there are collisions among particles that depend on their cross-sectional size, the average distance that a particle travels between collisions depends on the density of gas particles. Cross sections can be computed for atomic collisions but also are used in the sub-atomic realm, the number density of scattering centers is designated by n. Solving this equation exhibits the exponential attenuation of the intensity, Φ = Φ0 e − n σ z where Φ0 is the initial flux. For light, this is called the Beer–Lambert law, consider a classical measurement where a single particle is scattered off a single stationary target particle. Conventionally, a coordinate system is used, with the target placed at the origin. The angle θ is the angle, measured between the incident beam and the scattered beam and the φ is the azimuthal angle. The impact parameter b is the offset of the trajectory of the incoming particle. For a given interaction, the parameter and the scattering angle have a definite one-to-one functional dependence on each other. Generally the impact parameter can neither be controlled nor measured from event to event and is assumed to all possible values when averaging over many scatterings. The differential size of the section is the area element in the plane of the impact parameter. The differential angular range of the particle at angle θ is the solid angle element d Ω = sin θ d θ d φ
16.
Catalysis
–
Catalysis is the increase in the rate of a chemical reaction due to the participation of an additional substance called a catalyst. In most cases, reactions occur faster with a catalyst because they require less activation energy, furthermore, since they are not consumed in the catalyzed reaction, catalysts can continue to act repeatedly. Often only tiny amounts are required in principle, in the presence of a catalyst, less free energy is required to reach the transition state, but the total free energy from reactants to products does not change. A catalyst may participate in multiple chemical transformations, the effect of a catalyst may vary due to the presence of other substances known as inhibitors or poisons or promoters. Catalyzed reactions have an activation energy than the corresponding uncatalyzed reaction, resulting in a higher reaction rate at the same temperature. However, the mechanics of catalysis is complex. Usually, the catalyst participates in this slowest step, and rates are limited by amount of catalyst, in heterogeneous catalysis, the diffusion of reagents to the surface and diffusion of products from the surface can be rate determining. A nanomaterial-based catalyst is an example of a heterogeneous catalyst, analogous events associated with substrate binding and product dissociation apply to homogeneous catalysts. Although catalysts are not consumed by the reaction itself, they may be inhibited, deactivated, in heterogeneous catalysis, typical secondary processes include coking where the catalyst becomes covered by polymeric side products. Additionally, heterogeneous catalysts can dissolve into the solution in a system or sublimate in a solid–gas system. The production of most industrially important chemicals involves catalysis, similarly, most biochemically significant processes are catalysed. Research into catalysis is a field in applied science and involves many areas of chemistry, notably organometallic chemistry. Catalysis is relevant to aspects of environmental science, e. g. the catalytic converter in automobiles. Many transition metals and transition metal complexes are used in catalysis as well, Catalysts called enzymes are important in biology. A catalyst works by providing a reaction pathway to the reaction product. The rate of the reaction is increased as this route has a lower activation energy than the reaction route not mediated by the catalyst. The disproportionation of hydrogen peroxide creates water and oxygen, as shown below,2 H2O2 →2 H2O + O2 This reaction is preferable in the sense that the reaction products are more stable than the starting material, though the uncatalysed reaction is slow. In fact, the decomposition of hydrogen peroxide is so slow that hydrogen peroxide solutions are commercially available and this reaction is strongly affected by catalysts such as manganese dioxide, or the enzyme peroxidase in organisms
17.
Standard enthalpy of formation
–
Its symbol is ΔHo f or ΔfHo. The superscript Plimsoll on this symbol indicates that the process has occurred under standard conditions at the specified temperature. One exception is phosphorus, for which the most stable form at 1 atm is black phosphorus and this is true for all enthalpies of formation. In physics the energy per particle is expressed in electronvolts. All elements in their states have a standard enthalpy of formation of zero. The formation reaction is a constant pressure and constant temperature process, since the pressure of the standard formation reaction is fixed at 1 atm, the standard formation enthalpy or reaction heat is a function of temperature. For tabulation purposes, standard formation enthalpies are all given at a temperature,298 K. The standard enthalpy of formation is equivalent to the sum of separate processes included in the Born–Haber cycle of synthesis reactions. This is because enthalpy is a state function, in the example above the standard enthalpy change of formation for sodium chloride is equal to the sum of the standard enthalpy change of formation for each of the steps involved in the process. This is especially useful for very long reactions with many intermediate steps, chemists may use standard enthalpies of formation for a reaction that is hypothetical. That it is shows that the reaction, if it were to proceed, would be exothermic. It is possible to heat of formations for simple unstrained organic compounds with the Heat of formation group additivity method. Standard enthalpies of formation are used in thermochemistry to find the enthalpy change of any reaction. This implies that the reaction is exothermic, the converse is also true, the standard enthalpy of reaction will be positive for an endothermic reaction. When a reaction is reversed, the magnitude of ΔH stays the same, when the balanced equation for a reaction is multiplied by an integer, the corresponding value of ΔH must be multiplied by that integer as well. Allotropes of an element other than the state generally have non-zero standard enthalpies of formation. Standard enthalpy of sublimation, or heat of sublimation, is defined as the required to sublime one mole of the substance under standard conditions. Standard enthalpy of solution is the change associated with the dissolution of a substance in a solvent at constant pressure under standard conditions
18.
Reaction coordinate
–
In chemistry, a reaction coordinate is an abstract one-dimensional coordinate which represents progress along a reaction pathway. It is usually a geometric parameter that changes during the conversion of one or more molecular entities, in molecular dynamics simulations, a reaction coordinate is called collective variable. These coordinates can sometimes represent a real system, although, for more complex reactions especially. Reaction coordinates are often plotted against free energy to demonstrate in some form the potential energy profile associated to the reaction. The reaction coordinate is typically chosen to follow the path along the gradient of potential energy from reactants to products, for example, in the homolytic dissociation of molecular hydrogen, an apt coordinate system to choose would be the coordinate corresponding to the bond length
19.
Enzyme
–
Enzymes /ˈɛnzaɪmz/ are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions, the molecules at the beginning of the process upon which enzymes may act are called substrates and the enzyme converts these into different molecules, called products. Almost all metabolic processes in the cell need enzymes in order to occur at rates fast enough to sustain life, the set of enzymes made in a cell determines which metabolic pathways occur in that cell. The study of enzymes is called enzymology, enzymes are known to catalyze more than 5,000 biochemical reaction types. Most enzymes are proteins, although a few are catalytic RNA molecules, enzymes specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the rate of a reaction by lowering its activation energy, some enzymes can make their conversion of substrate to product occur many millions of times faster. An extreme example is orotidine 5-phosphate decarboxylase, which allows a reaction that would take millions of years to occur in milliseconds. Chemically, enzymes are like any catalyst and are not consumed in chemical reactions, enzymes differ from most other catalysts by being much more specific. Enzyme activity can be affected by other molecules, inhibitors are molecules that decrease enzyme activity, many drugs and poisons are enzyme inhibitors. An enzymes activity decreases markedly outside its optimal temperature and pH, some enzymes are used commercially, for example, in the synthesis of antibiotics. French chemist Anselme Payen was the first to discover an enzyme, diastase and he wrote that alcoholic fermentation is an act correlated with the life and organization of the yeast cells, not with the death or putrefaction of the cells. In 1877, German physiologist Wilhelm Kühne first used the term enzyme, the word enzyme was used later to refer to nonliving substances such as pepsin, and the word ferment was used to refer to chemical activity produced by living organisms. Eduard Buchner submitted his first paper on the study of yeast extracts in 1897, in a series of experiments at the University of Berlin, he found that sugar was fermented by yeast extracts even when there were no living yeast cells in the mixture. He named the enzyme that brought about the fermentation of sucrose zymase, in 1907, he received the Nobel Prize in Chemistry for his discovery of cell-free fermentation. Following Buchners example, enzymes are usually named according to the reaction they carry out, the biochemical identity of enzymes was still unknown in the early 1900s. Sumner showed that the enzyme urease was a protein and crystallized it. These three scientists were awarded the 1946 Nobel Prize in Chemistry, the discovery that enzymes could be crystallized eventually allowed their structures to be solved by x-ray crystallography. This high-resolution structure of lysozyme marked the beginning of the field of structural biology, an enzymes name is often derived from its substrate or the chemical reaction it catalyzes, with the word ending in -ase
20.
Transition state
–
The transition state of a chemical reaction is a particular configuration along the reaction coordinate. It is defined as the corresponding to the highest potential energy along this reaction coordinate. At this point, assuming a perfectly irreversible reaction, colliding reactant molecules always go on to form products and it is often marked with the double dagger ‡ symbol. The concept of a state has been important in many theories of the rates at which chemical reactions occur. This started with the state theory, which was first developed around 1935 by Eyring, Evans and Polanyi. A collision between reactant molecules may or may not result in a successful reaction, the outcome depends on factors such as the relative kinetic energy, relative orientation and internal energy of the molecules. Even if the partners form an activated complex they are not bound to go on and form products. Because of the rules of quantum mechanics, the state cannot be captured or directly observed. This is sometimes expressed by stating that the state has a fleeting existence. However, cleverly manipulated spectroscopic techniques can get us as close as the timescale of the technique allows, femtochemical IR spectroscopy was developed for precisely that reason, and it is possible to probe molecular structure extremely close to the transition point. Often along the reaction coordinate reactive intermediates are present not much lower in energy from a transition state making it difficult to distinguish between the two, Transition state structures can be determined by searching for first-order saddle points on the potential energy surface of the chemical species of interest. A first-order saddle point is a point of index one, that is. This is further described in the geometry optimization. The Hammond–Leffler Postulate states that the structure of the state more closely resembles either the products or the starting material. A transition state resembles the reactants more than the products is said to be early. Thus, the Hammond–Leffler Postulate predicts a transition state for an endothermic reaction. A dimensionless reaction coordinate that quantifies the lateness of a state can be used to test the validity of the Hammond–Leffler Postulate for a particular reaction. One demonstration of principle is found in the two bicyclic compounds depicted below
21.
Gibbs free energy
–
Just as in mechanics, where the decrease in potential energy is defined as maximum useful work that can be performed, similarly different potentials have different meanings. The Gibbs energy is also the potential that is minimized when a system reaches chemical equilibrium at constant pressure and temperature. Its derivative with respect to the coordinate of the system vanishes at the equilibrium point. As such, a reduction in G is a condition for the spontaneity of processes at constant pressure and temperature. The Gibbs free energy, originally called available energy, was developed in the 1870s by the American scientist Josiah Willard Gibbs. The initial state of the body, according to Gibbs, is supposed to be such that the body can be made to pass from it to states of dissipated energy by reversible processes. In his 1876 magnum opus On the Equilibrium of Heterogeneous Substances, according to the second law of thermodynamics, for systems reacting at STP, there is a general natural tendency to achieve a minimum of the Gibbs free energy. A quantitative measure of the favorability of a reaction at constant temperature and pressure is the change ΔG in Gibbs free energy that is caused by the reaction. As a necessary condition for the reaction to occur at constant temperature and pressure, ΔG must be smaller than the non-PV work, ΔG equals the maximum amount of non-PV work that can be performed as a result of the chemical reaction for the case of reversible process. The equation can be seen from the perspective of the system taken together with its surroundings. First assume that the reaction at constant temperature and pressure is the only one that is occurring. Then the entropy released or absorbed by the system equals the entropy that the environment must absorb or release, the reaction will only be allowed if the total entropy change of the universe is zero or positive. This is reflected in a negative ΔG, and the reaction is called exergonic, if we couple reactions, then an otherwise endergonic chemical reaction can be made to happen. In traditional use, the term free was included in Gibbs free energy to mean available in the form of useful work, the characterization becomes more precise if we add the qualification that it is the energy available for non-volume work. However, a number of books and journal articles do not include the attachment free. This is the result of a 1988 IUPAC meeting to set unified terminologies for the scientific community. This standard, however, has not yet been universally adopted. Further, Gibbs stated, In this description, as used by Gibbs, ε refers to the energy of the body, η refers to the entropy of the body
22.
Entropy
–
In statistical thermodynamics, entropy is a measure of the number of microscopic configurations Ω that a thermodynamic system can have when in a state as specified by some macroscopic variables. Formally, S = k B ln Ω, for example, gas in a container with known volume, pressure, and temperature could have an enormous number of possible configurations of the collection of individual gas molecules. Each instantaneous configuration of the gas may be regarded as random, Entropy may be understood as a measure of disorder within a macroscopic system. The second law of thermodynamics states that an isolated systems entropy never decreases, such systems spontaneously evolve towards thermodynamic equilibrium, the state with maximum entropy. Non-isolated systems may lose entropy, provided their environments entropy increases by at least that amount, since entropy is a function of the state of the system, a change in entropy of a system is determined by its initial and final states. This applies whether the process is reversible or irreversible, however, irreversible processes increase the combined entropy of the system and its environment. The above definition is called the macroscopic definition of entropy because it can be used without regard to any microscopic description of the contents of a system. The concept of entropy has found to be generally useful and has several other formulations. Entropy was discovered when it was noticed to be a quantity that behaves as a function of state and it has the dimension of energy divided by temperature, which has a unit of joules per kelvin in the International System of Units. But the entropy of a substance is usually given as an intensive property—either entropy per unit mass or entropy per unit amount of substance. In statistical mechanics this reflects that the state of a system is generally non-degenerate. Understanding the role of entropy in various processes requires an understanding of how. It is often said that entropy is an expression of the disorder, or randomness of a system, the second law is now often seen as an expression of the fundamental postulate of statistical mechanics through the modern definition of entropy. In other words, in any natural process there exists an inherent tendency towards the dissipation of useful energy and he made the analogy with that of how water falls in a water wheel. This was an insight into the second law of thermodynamics. g. Clausius described entropy as the transformation-content, i. e. dissipative energy use and this was in contrast to earlier views, based on the theories of Isaac Newton, that heat was an indestructible particle that had mass. Later, scientists such as Ludwig Boltzmann, Josiah Willard Gibbs, henceforth, the essential problem in statistical thermodynamics, i. e. according to Erwin Schrödinger, has been to determine the distribution of a given amount of energy E over N identical systems. Carathéodory linked entropy with a definition of irreversibility, in terms of trajectories
23.
Chemical kinetics
–
Chemical kinetics, also known as reaction kinetics, is the study of rates of chemical processes. Van t Hoff studied chemical dynamics and published in 1884 his famous Etudes de dynamique chimique, after van t Hoff, chemical kinetics deals with the experimental determination of reaction rates from which rate laws and rate constants are derived. Relatively simple rate laws exist for zero order reactions, first order reactions, and second order reactions, and can be derived for others. Elementary reactions follow the law of action, but the rate law of stepwise reactions has to be derived by combining the rate laws of the various elementary steps. In consecutive reactions, the rate-determining step often determines the kinetics, in consecutive first order reactions, a steady state approximation can simplify the rate law. The activation energy for a reaction is determined through the Arrhenius equation. Gorban and Yablonsky have suggested that the history of chemical dynamics can be divided into three eras, the first is the van t Hoff wave searching for the general laws of chemical reactions and relating kinetics to thermodynamics. The second may be called the Semenov--Hinshelwood wave with emphasis on reaction mechanisms, the third is associated with Aris and the detailed mathematical description of chemical reaction networks. Depending upon what substances are reacting, the rate varies. Acid/base reactions, the formation of salts, and ion exchange are fast reactions, when covalent bond formation takes place between the molecules and when large molecules are formed, the reactions tend to be very slow. Nature and strength of bonds in reactant molecules greatly influence the rate of its transformation into products, the physical state of a reactant is also an important factor of the rate of change. When reactants are in the phase, as in aqueous solution. However, when they are in different phases, the reaction is limited to the interface between the reactants, reaction can occur only at their area of contact, in the case of a liquid and a gas, at the surface of the liquid. Vigorous shaking and stirring may be needed to bring the reaction to completion and this means that the more finely divided a solid or liquid reactant the greater its surface area per unit volume and the more contact it with the other reactant, thus the faster the reaction. To make an analogy, for example, when one starts a fire, one uses wood chips, in organic chemistry, on water reactions are the exception to the rule that homogeneous reactions take place faster than heterogeneous reactions. In a solid, only those particles that are at the surface can be involved in a reaction, for example, Sherbet is a mixture of very fine powder of malic acid and sodium hydrogen carbonate. On contact with the saliva in the mouth, these chemicals quickly dissolve and react, releasing carbon dioxide, also, fireworks manufacturers modify the surface area of solid reactants to control the rate at which the fuels in fireworks are oxidised, using this to create different effects. For example, finely divided aluminium confined in a shell explodes violently, if larger pieces of aluminium are used, the reaction is slower and sparks are seen as pieces of burning metal are ejected
24.
Quantum tunnelling
–
Quantum tunnelling or tunneling refers to the quantum mechanical phenomenon where a particle tunnels through a barrier that it classically could not surmount. This plays an role in several physical phenomena, such as the nuclear fusion that occurs in main sequence stars like the Sun. It has important applications to modern devices such as the diode, quantum computing. The effect was predicted in the early 20th century and its acceptance as a physical phenomenon came mid-century. Tunnelling is often explained using the Heisenberg uncertainty principle and the duality of matter. Pure quantum mechanical concepts are central to the phenomenon, so quantum tunnelling is one of the implications of quantum mechanics. Quantum tunnelling was developed from the study of radioactivity, which was discovered in 1896 by Henri Becquerel, radioactivity was examined further by Marie Curie and Pierre Curie, for which they earned the Nobel Prize in Physics in 1903. Ernest Rutherford and Egon Schweidler studied its nature, which was later verified empirically by Friedrich Kohlrausch, the idea of the half-life and the impossibility of predicting decay was created from their work. J. J. Thomson commented the finding warranted further investigation, in 1926, Rother, using a still newer platform galvanometer of sensitivity 26 pA, measured the field emission currents in a hard vacuum between closely spaced electrodes. Friedrich Hund was the first to notice of tunnelling in 1927 when he was calculating the ground state of the double-well potential. Its first application was an explanation for alpha decay, which was done in 1928 by George Gamow and independently by Ronald Gurney. After attending a seminar by Gamow, Max Born recognised the generality of tunnelling and he realised that it was not restricted to nuclear physics, but was a general result of quantum mechanics that applies to many different systems. Shortly thereafter, both considered the case of particles tunnelling into the nucleus. The study of semiconductors and the development of transistors and diodes led to the acceptance of electron tunnelling in solids by 1957. The work of Leo Esaki, Ivar Giaever and Brian Josephson predicted the tunnelling of superconducting Cooper pairs, in 2016, the quantum tunneling of water was discovered. Quantum tunnelling falls under the domain of quantum mechanics, the study of what happens at the quantum scale and this process cannot be directly perceived, but much of its understanding is shaped by the microscopic world, which classical mechanics cannot adequately explain. Classical mechanics predicts that particles that do not have enough energy to surmount a barrier will not be able to reach the other side. Thus, a ball without sufficient energy to surmount the hill would roll back down, or, lacking the energy to penetrate a wall, it would bounce back or in the extreme case, bury itself inside the wall
25.
Dust explosion
–
A dust explosion is the rapid combustion of fine particles suspended in the air, often but not always in an enclosed location. Dust explosions can occur where any dispersed powdered combustible material is present in high concentrations in the atmosphere or other oxidizing gaseous medium such as oxygen. Dust explosions are a frequent hazard in coal mines, in grain elevators. If rapid combustion occurs in a space, enormous overpressures can build up, causing major structural damage. The sudden release of energy from a detonation can produce a shockwave, if the spread of flame is at subsonic speed, the phenomenon is sometimes called a deflagration, although looser usage calls both phenomena explosions. Dust explosions may be classified as being either primary or secondary in nature, primary dust explosions may occur inside process equipment or similar enclosures, and are generally controlled by pressure relief through purpose-built ducting to the external atmosphere. Historically, fatalities from dust explosions have largely been the result of secondary dust explosions, many common materials which are known to burn can generate a dust explosion, such as coal and sawdust. In addition, many otherwise mundane organic materials can also be dispersed into a dangerous dust cloud, such as grain, flour, starch, sugar, powdered milk, cocoa, coffee, powdered metals can form explosive suspensions in air, if finely divided. Explosive dust can arise from such as transporting grain. Mining of coal leads to coal dust, and flour mills likewise have large amounts of flour dust as a result of milling. A gigantic explosion of flour dust destroyed a mill in Minnesota on May 2,1878, killing 14 workers at the Washburn A Mill, a similar problem occurs in sawmills and other places dedicated to woodworking. Although not strictly a dust, paper particles emitted during processing - especially rolling, unrolling, calendaring/slitting, enclosed paper mill areas subject to such dangers commonly maintain very high air humidities to reduce the chance of airborne paper dust explosions. In special effects pyrotechnics, lycopodium powder and non-dairy creamer are two means of producing safe, controlled fire effects. Thermobaric weapons, depending upon their fuel, are also a potential and intentional source of dust, below a certain value, the lower explosive limit, there is simply insufficient dust to support the combustion at the rate required for an explosion. A combustible concentration at or below 25% of the LEL is considered safe, similarly, if the fuel/air ratio increases above the upper explosive limit, there is insufficient oxidant to permit combustion to continue at the necessary rate. Typically, normal atmospheric oxygen can be sufficient to support a dust explosion if the necessary conditions are also present. High-oxygen or pure oxygen environments are considered to be especially hazardous, there are many sources of ignition, and a naked flame need not be the only one, over one half of the dust explosions in Germany in 2005 were from non-flame sources. When a source cannot be found, ignition will often be attributed to static electricity, static charges can be generated by external sources, or can be internally generated by friction at the surfaces of particles themselves as they collide or move past one another
26.
Spark plug
–
A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. The central electrode, which may contain a resistor, is connected by an insulated wire to the output terminal of an ignition coil or magneto. The spark plugs shell is screwed into the engines cylinder head. Spark plugs may also be used in applications such as furnaces wherein a combustible fuel/air mixture must be ignited. In this case, they are referred to as flame igniters. In 1860 Étienne Lenoir used a spark plug in his gas engine. Early patents for spark plugs included those by Nikola Tesla, Frederick Richard Simms, helen Blair Bartlett also played a vital role in making the insulator in 1930. The plug is connected to the voltage generated by an ignition coil or magneto. As current flows from the coil, a voltage develops between the central and side electrodes. Initially no current can flow because the fuel and air in the gap is an insulator, once the voltage exceeds the dielectric strength of the gases, the gases become ionized. The ionized gas becomes a conductor and allows current to flow across the gap, spark plugs usually require voltage of 12, 000–25,000 volts or more to fire properly, although it can go up to 45,000 volts. They supply higher current during the process, resulting in a hotter. As the current of electrons surges across the gap, it raises the temperature of the channel to 60,000 K. The intense heat in the channel causes the ionized gas to expand very quickly. This is the click heard when observing a spark, similar to lightning and thunder. The heat and pressure force the gases to react with each other, the size of this fireball, or kernel, depends on the exact composition of the mixture between the electrodes and the level of combustion chamber turbulence at the time of the spark. A small kernel will make the run as though the ignition timing was retarded. A spark plug is composed of a shell, insulator and the central conductor, spark plugs are specified by size, either thread or nut, sealing type, and spark gap
27.
Fire making
–
Fire making, fire lighting or fire craft is the process of starting a fire artificially. It requires completing the fire triangle, usually by heating tinder above its autoignition temperature, Fire is an essential tool for survival and was important in early human cultural development. Today, its a key component of Scouting and bushcraft, fine tinder is a material that combusts first and in doing so heats other material until it burns. Fine tinder is characterized by its ability to combust from a spark, friction, autognition temperatures of common tinder, Tinder is preserved within a Tinderbox, which today is often a plastic bag. Tinder when formed into a tight bundle can also be used to preserve/carry an ember, often in the form of a cigar and made of compacted tinder materials held within a tinderbox, a smouldering ember could safely be saved inside. Fire occurs naturally as a result of activity, meteorites. Many animals are aware of fire and adapt their behavior to it, plants, too, have adapted to the natural occurrence of fire. Thus, humans encountered and were aware of fire, and later its beneficial uses, natural sources of animal fats and petrochemicals that burn could have been used to keep and maintain fires that started naturally. Fire can be created through friction by rapidly grinding pieces of solid combustable material against each other which are heated, successfully creating fire by friction involves skill, fitness, knowledge, and acceptable environmental conditions. Once hot enough, the ember is introduced to the tinder, more oxygen is added by blowing and this repeated spinning and downward pressure causes black dust to form in the notch of the fireboard, eventually creating a hot, glowing coal. The coal is then carefully placed among dense, fine tinder, the advantage of the hand drill technique is that it requires no rope. The bow drill uses the principle as the hand drill but the spindle is shorter, wider and driven by a bow. Additional downward pressure is generated by the handhold, a pump drill is a variant of the bow drill that uses a coiled rope around a cross-section of wooden stake spin the shaft by pumping up and down a cross-member. The fire plough or fireplow consists of a cut to a dull point. The stake is pressed down hard and rubbed quickly against the groove of the piece in a plowing motion. A split is made down the length of the grooved piece. A fire-saw is a method by which a piece of wood is sawed through a notch in a piece or pieces to generate friction. The tinder may be placed between two slats of wood with the piece or saw drawn over them above the tinder so as to catch a coal
28.
Bonfire
–
A bonfire is a large but controlled outdoor fire, used either for informal disposal of burnable waste material or as part of a celebration. In many regions of continental Europe, bonfires are traditionally on 16 January. Bonfires are also a feature of Walpurgis Night in central and northern Europe, in Finland bonfires are tradition on Midsummer Eve and Easter, also in midst of May celebrations. Bonfire traditions of early spring, lit on the Sunday following Ash Wednesday, are throughout the Alemannic German speaking regions of Europe. The burning of winter in effigy at the Sechseläuten in Zürich is inspired by this Alemannic tradition, in Austria Osterfeuer, Easter fires, are widespread, but also regulated in some cities, districts and countries to hold down the resulting annual peak of PM10-dust immission. There are also Sonnwendfeuer ignited on the evening of 21 June, since 1988 Feuer in den Alpen have been lit on a day in August on mountains so they can be seen from afar as an appeal for sustainable development of mountain regions. In the Czech Republic, the festival called Burning the Witches takes place on the night between 30 April and 1 May and this is a very old and still observed folk custom and special holiday. On that night, people together, light bonfires. In many places people erect maypoles, the night between 30 April and 1 May was considered magical. The festival was originally celebrated when the moon was full closest to the day exactly between the spring equinox and summer solstice. People believed that on this night witches fly on the Sabbath, people also believed, for example, in the opening of various caves and underground caverns in which treasures are hidden. The main purpose of this old folk custom was probably a celebration of fertility, to protect themselves against witches, people lit bonfires in high places, calling these fires Burning the Witches. Some people took to jumping over the fire in order to ensure youth, the ash from these fires supposedly had a special power to raise crops, and people also walked the cattle through the ashes to ensure fertility. In Australia, bonfires may be lit to celebrate Commonwealth Day or the Queens Official Birthday, in the province of Quebec, many communities light up bonfires on 24 June to celebrate Saint-Jean-Baptiste Day. In France, the bonfire celebrates Saint Jean le Baptiste during the Fête de la Saint Jean, first saturday after the solstice, like the other countries, it was a pagan celebration of the solstice, or midsummer, but christianisation transformed it into a catholic celebration. People have bonfires on communal land, if there has been a recent wedding or a new born in the family, people will have a bonfire outside their house to celebrate this event. The festival falls in the week of January every year. In Assam in the part of India, a harvest festival called Bhogali Bihu is celebrated to mark the end of the harvest season in mid-January
29.
Glossary of firelighting
–
This is an alphabetized glossary of terms pertaining to lighting fires, along with their definitions. Firelighting is the process of starting a fire artificially, fire was an essential tool in early human cultural development. It requires completing the fire triangle, usually by initiating the combustion of a suitably flammable material, amadou – a spongy, flammable substance prepared from bracket fungi. Arson – the crime of intentionally or maliciously lighting structures, wildland areas and it is the deliberate setting of fires for personal, monetary or political gain. Auto reignition – a process used in gas burners to control ignition devices based on whether a burner flame is lit. Autoignition temperature – the lowest temperature at which a substance will ignite in a normal atmosphere without an external source of ignition. Batoning – the technique of cutting or splitting wood by using a stick or mallet to repeatedly strike the spine of a sturdy knife. The batoning method can be used to make kindling or desired forms such as boards, the practice is most useful for obtaining dry wood from the inside of logs for the purpose of fire making. Black match – in pyrotechnics, a type of crude fuse, blow George – an implement used in fire lighting, used to increase the efficiency of firelighting through acceleration of the chimney draw. Bow drill – an ancient tool usually used to make fire and it was also used for primitive woodworking and dentistry. Bridgewire – a relatively thin resistance wire used to set off a pyrotechnic composition serving as pyrotechnic initiator, Bryant and May – a United Kingdom company created in the mid-nineteenth century specifically to make matches. Burning glass – a large convex lens that can concentrate the suns rays onto an area, heating up the area. Campfire – a fire lit at a campsite, to serve the functions, light, warmth, a beacon, an insect and/or apex predator deterrent, to cook. Char cloth – a swatch of fabric made from vegetable fiber that has been converted via pyrolysis into a fuel of very low ignition temperature. Combustion – the sequence of chemical reactions between a fuel and an oxidant accompanied by the production of heat and conversion of chemical species. The release of heat can result in the production of light in the form of either glowing or a flame, control of fire by early humans – A turning point in the cultural aspect of human evolution that allowed humans to cook food and obtain warmth and protection. Making fire also allowed the expansion of human activity into the hours of the night. Dickheads – a brand of matches released by Australian businessman Dick Smith in 1999, the name is a pun on the Redheads brand of matches
30.
Ember
–
An ember is a glowing, hot coal made of greatly heated wood, coal, or other carbon-based material that remain after, or sometimes precede, a fire. Embers can glow very hot, sometimes as hot as the fire which created them, in order to avoid the danger of accidentally spreading a fire, many campers pour water on the embers or cover them in dirt. They are often used for cooking, such as in charcoal barbecues and this is because embers radiate a more constant form of heat, as opposed to an open fire which is constantly changing along with the heat it radiates. An ember is formed when a fire has only partially burnt a piece of fuel. Often this happens because the chemical energy is so deep into the center that air does not reach it. It continues to stay hot and does not lose its thermal energy quickly because combustion is still happening at a low level, the small yellow, orange and red lights often seen among the embers are actually combustion. There just is not enough combustion happening at one time to create a flame, once the embers are completely burned through, they are not carbon as is commonly believed, but rather various other oxidized minerals like calcium and phosphorus. At that point they are called ashes. See, Wood ash for more on the residue that is left, embers play a large role in forest fires. Since embers are typically burnt leaves and thus small and lightweight, during a large fire, with the right wind conditions, embers can be blown far ahead of the fire front, starting spot fires several kilometres away. A number of measures can be undertaken by homeowners to reduce the consequences of such an ember attack that bombards especially wooden structures
31.
Fire triangle
–
The fire triangles or combustion triangles or ″fire diamond″ are simple models for understanding the necessary ingredients for most fires. The triangle illustrates the three elements a fire needs to ignite, heat, fuel, and an oxidizing agent, a fire naturally occurs when the elements are present and combined in the right mixture, meaning that fire is actually an event rather than a thing. A fire can be prevented or extinguished by removing any one of the elements in the fire triangle, for example, covering a fire with a fire blanket removes the oxygen part of the triangle and can extinguish a fire. In large fires where firefighters are called in, decreasing the amount of oxygen is not usually an option because there is no way to make that happen in an extended area. Not to be confused with NFPA704, also called the fire diamond, the fire tetrahedron represents the addition of a component in the chemical chain reaction, to the three already present in the fire triangle. Once a fire has started, the resulting chain reaction sustains the fire. Foam can be used to deny the fire the oxygen it needs, water can be used to lower the temperature of the fuel below the ignition point or to remove or disperse the fuel. Halon can be used to free radicals and create a barrier of inert gas in a direct attack on the chemical reaction responsible for the fire. Combustion is the reaction that feeds a fire more heat. When the fire involves burning metals like lithium, magnesium, titanium, the metals react faster with water than with oxygen and thereby more energy is released. Putting water on such a fire results in the fire getting hotter or even exploding, carbon dioxide extinguishers are ineffective against certain metals such as titanium. Therefore, inert agents must be used to break the chain reaction of metallic combustion, in the same way, as soon as one of the four elements of the tetrahedron is removed, combustion stops. The oxidizer is the other reactant of the chemical reaction, in most cases, it is the ambient air, and in particular one of its components, oxygen. In certain torches, gaseous oxygen is introduced to improve combustion, some chemicals, such as fluorine gas, perchlorate salts such as ammonium perchlorate, or chlorine trifluoride, act as oxidisers, sometimes more powerful ones than oxygen itself. A fire based on a reaction with these oxidisers can be difficult to put out until the oxidiser is exhausted. In certain cases such as explosives, the oxidizer and combustible are the same. Reaction is initiated by an energy, in most cases. Several examples include friction, as in case of matches, heating an electrical wire, there are also many other ways to bring sufficient activation energy including electricity, radiation, and pressure, all of which will lead to a temperature rise
32.
Firewood
–
Firewood is any wooden material that is gathered and used for fuel. Generally, firewood is not highly processed and is in some sort of recognizable log or branch form, Firewood can be seasoned or unseasoned. It can be classed as hardwood or softwood, however, demand for this fuel can outpace its ability to regenerate on a local or regional level. Good forestry practices and improvements in devices that use firewood can improve local wood supplies, harvesting or collecting firewood varies by the region and culture. Some places have specific areas for firewood collection, other places may integrate the collection of firewood in the cycle of preparing a plot of land to grow food as part of a field rotation process. Collection can be a group, family or an individual activity, the tools and methods for harvesting firewood are diverse. Some firewood is harvested in woodlots managed for that purpose, deadfall that has not started to rot is preferred, since it is already partly seasoned. Standing dead timber is considered better still, for it has less dirt on the trunk, allowing tools to stay sharper longer, harvesting this form of timber reduces the speed and intensity of bushfires, but it also reduces habitat for snag-nesting animals such as owls and some rodents. Harvesting timber for firewood is normally carried out by hand with chainsaws, thus, longer pieces - requiring less manual labour, and less chainsaw fuel - are less expensive and only limited by the size of the firebox. In most of the United States, the measure of firewood is a cord or 128 cubic feet, however. The BTU value can affect the price, prices also vary considerably with the distance from wood lots, and quality of the wood. Buying and burning firewood that was cut only a distance from its final destination prevents the accidental spread of invasive tree-killing insects. In most parts of the world, firewood is only prepared for transport at the time it is harvested, then it is moved closer to the place it will be used as fuel and prepared there. The process of making charcoal from firewood can take place at the place the firewood is harvested, most firewood also requires splitting, which also allows for faster seasoning by exposing more surface area. Today most splitting is done with a hydraulic splitting machine, another method is to use a kinetic log splitter, which uses a rack and pinion system powered by a small motor and a large flywheel used for energy storage. There are many ways to store firewood and these range from simple piles to free-standing stacks, to specialized structures. Usually the goal of storing wood is to keep away from it. Stacks, The simplest stack is where logs are placed next to and on top of each other, the height of the stack can vary, generally depending upon how the ends are constructed
33.
Spark (fire)
–
A spark is an incandescent particle. Such sparks may be produced by pyrotechnics, by metalworking or as a by-product of fires, in pyrotechnics, iron filings and metal alloys such as magnalium may be used to create sparks. The quantity and style of sparks produced depends on the composition and pyrophoricity of the metal, in the case of iron, the presence of carbon is required, as in carbon steel — about 0. 7% is best for large sparks. The carbon burns explosively in the hot iron and this produces pretty, the duration of the existence of a spark is determined by the initial size of the particle, with a larger size leading to a longer-lasting spark. Metals with low thermal conductivity are especially good at producing sparks, titanium and zirconium are especially good in this respect and so are now used in fireworks. Copper, on the hand, has a high conductivity. For this reason, alloys of copper such as beryllium bronze are used to make safety tools which will not spark so easily, robert Hooke studied the sparks created by striking a piece of flint and steel together. He found that the sparks were usually particles of the steel which had become red hot and these sparks can be used to ignite tinder and so start a fire. In colonial America, flint and steel were used to light fires when easier methods failed, scorched linen was commonly used as tinder to catch the spark and start the fire but producing a good spark could take much time. A spinning steel wheel provided a stream of sparks when it engaged the flint. In a modern lighter or firesteel, iron is mixed with cerium and this readily produces sparks when scraped and burns hotter than steel would. This higher temperature is needed to ignite the vapour of the lighter fluid, molten metal sparks can be created when metal is heated by processes such as Bessemer conversion of iron to steel or arc welding. Arc welding uses a low voltage and high current electric arc between an electrode and the material to melt the metals at the welding point, which often creates sparks. To reduce the risk of burns, welders wear heavy leather gloves and long sleeve jackets to avoid exposure to heat, flames. In spot welding, metal surfaces that are held in contact are joined by the heat resistance to electric current flow. It is common for a spray of sparks in the form of metal droplets to be ejected from the parts being joined. Or the resistance heating of spot welding, fires may produce sparks as updrafts carry particles of the burning fuel aloft. This was a problem with steam locomotives as the sparks might set fire to the adjacent landscape or even to the train itself
34.
Wood ash
–
Wood ash is the residue powder left after the combustion of wood, such as burning wood in a home fireplace or an industrial power plant. It is used traditionally by gardeners as a source of potash. Many studies have been conducted regarding the composition of wood ash. Some quote calcium carbonate as the constituent, others find no carbonate at all. Some show as much as twelve percent iron oxide while others show none, a comprehensive set of analyses of wood ash composition from many tree species has been carried out by Emil Wolff, among others. Several factors have a impact on the composition, Fly ash, Some studies include the solids escaping via the flue during combustion. Temperature of combustion produces two direct effects, Dissociation, Conversion of carbonates, sulfides, etc. to oxides results in no carbon, sulfur, carbonates, Some metallic oxides even dissociate to their elemental state and/or vaporize completely at wood fire temperatures. Volatilization, In studies in which the fly ash is not measured, experimental process, If the ashes are exposed to the environment between combustion and the analysis, oxides may convert back to carbonates by reacting with carbon dioxide in the air. Type, age, and growing environment of the wood stock affect the composition of the wood, typically between 0.43 and 1.82 percent of the mass of burned wood results in ash. Also the conditions of the affect the composition and amount of the residue ash. Much wood ash contains calcium carbonate as its major component, representing 25 or even 45 percent, less than 10 percent is potash, and less than 1 percent phosphate, there are trace elements of iron, manganese, zinc, copper and some heavy metals. However, these numbers vary, as temperature is an important variable in determining wood ash composition. All of these are, primarily, in the form of oxides, wood ash can be used as an organic fertilizer used to enrich agricultural soil nutrition. In this role, wood ash serves a source of potassium and calcium carbonate, wood ash can also be used as an amendment for organic hydroponic solutions, generally replacing inorganic compounds containing calcium, potassium, magnesium and phosphorus. Because wood ash has a high content, it can be used as an odor control agent. Wood ash has a long history of being used in ceramic glazes, particularly in the Chinese, Japanese and Korean traditions. It acts as a flux, reducing the melting point of the glaze, potassium hydroxide can be made directly from wood ash and in this form, is known as caustic potash or lye. Because of this property, wood ash has also traditionally used to make wood-ash soap
35.
Wood fuel
–
Wood fuel is a fuel, such as firewood, charcoal, chips, sheets, pellets, and sawdust. The particular form used depends upon factors such as source, quantity, quality, sawmill waste and construction industry by-products also include various forms of lumber tailings. The discovery of how to fire for the purpose of burning wood is regarded as one of humanitys most important advances. The use of wood as a source for heating is much older than civilization and is assumed to have been used by Neanderthals. Today, burning of wood is the largest use of energy derived from a solid fuel biomass, Wood fuel can be used for cooking and heating, and occasionally for fueling steam engines and steam turbines that generate electricity. Wood may be used indoors in a furnace, stove, or fireplace, or outdoors in a furnace, campfire, in permanent structures and in caves, hearths were constructed or established—surfaces of stone or another noncombustible material upon which a fire could be built. Smoke escaped through a hole in the roof. In contrast to civilizations in relatively arid regions, the Greeks, Romans, Celts, Britons, over the centuries there was a partial deforestation of climax forests and the evolution of the remainder to coppice with standards woodland as the primary source of wood fuel. These woodlands involved a continuous cycle of new stems harvested from old stumps, one of the earliest printed books on woodland management, in English, was John Evelyns Sylva, or a discourse on forest trees advising landowners on the proper management of forest estates. H. L. Edlin, in Woodland Crafts in Britain,1949 outlines the extraordinary techniques employed, and throughout this time the preferred form of wood fuel was the branches of cut coppice stems bundled into faggots. Larger, bent or deformed stems that were of no use to the woodland craftsmen were converted to the end of World War two. Since then much of these woodlands have been converted to broadscale agriculture, during the Edo period of Japan, wood was used for many purposes, and the consumption of wood led Japan to develop a forest management policy during that era. Demand for timber resources was on the not only for fuel, but also for construction of ships and buildings. As a result, forest fires occurred, along with floods, around 1666, the shogun made it a policy to reduce logging and increase the planting of trees. This policy decreed that only the shogun, or a daimyō, by the 18th century, Japan had developed detailed scientific knowledge about silviculture and plantation forestry. The development of the chimney and the allowed for more effective exhaustion of the smoke. Masonry heaters or stoves went a further by capturing much of the heat of the fire and exhaust in a large thermal mass. The metal stove was a technological development concurrent with the industrial revolution, stoves were manufactured or constructed pieces of equipment that contained the fire on all sides and provided a means for controlling the draft—the amount of air allowed to reach the fire
