1.
Gas
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Gas is one of the four fundamental states of matter. A pure gas may be made up of atoms, elemental molecules made from one type of atom. A gas mixture would contain a variety of pure gases much like the air, what distinguishes a gas from liquids and solids is the vast separation of the individual gas particles. This separation usually makes a colorless gas invisible to the human observer, the interaction of gas particles in the presence of electric and gravitational fields are considered negligible as indicated by the constant velocity vectors in the image. One type of commonly known gas is steam, the gaseous state of matter is found between the liquid and plasma states, the latter of which provides the upper temperature boundary for gases. Bounding the lower end of the temperature scale lie degenerative quantum gases which are gaining increasing attention, high-density atomic gases super cooled to incredibly low temperatures are classified by their statistical behavior as either a Bose gas or a Fermi gas. For a comprehensive listing of these states of matter see list of states of matter. The only chemical elements which are stable multi atom homonuclear molecules at temperature and pressure, are hydrogen, nitrogen and oxygen. These gases, when grouped together with the noble gases. Alternatively they are known as molecular gases to distinguish them from molecules that are also chemical compounds. The word gas is a neologism first used by the early 17th-century Flemish chemist J. B. van Helmont, according to Paracelsuss terminology, chaos meant something like ultra-rarefied water. An alternative story is that Van Helmonts word is corrupted from gahst and these four characteristics were repeatedly observed by scientists such as Robert Boyle, Jacques Charles, John Dalton, Joseph Gay-Lussac and Amedeo Avogadro for a variety of gases in various settings. Their detailed studies ultimately led to a relationship among these properties expressed by the ideal gas law. Gas particles are separated from one another, and consequently have weaker intermolecular bonds than liquids or solids. These intermolecular forces result from interactions between gas particles. Like-charged areas of different gas particles repel, while oppositely charged regions of different gas particles attract one another, transient, randomly induced charges exist across non-polar covalent bonds of molecules and electrostatic interactions caused by them are referred to as Van der Waals forces. The interaction of these forces varies within a substance which determines many of the physical properties unique to each gas. A comparison of boiling points for compounds formed by ionic and covalent bonds leads us to this conclusion, the drifting smoke particles in the image provides some insight into low pressure gas behavior
2.
Soft drink
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A soft drink is a drink that typically contains carbonated water, a sweetener, and a natural or artificial flavoring. The sweetener may be sugar, high-fructose corn syrup, fruit juice, sugar substitutes, Soft drinks may also contain caffeine, colorings, preservatives, and other ingredients. Soft drinks are called soft in contrast to hard drinks, small amounts of alcohol may be present in a soft drink, but the alcohol content must be less than 0. 5% of the total volume if the drink is to be considered non-alcoholic. Fruit punch, tea, and other such non-alcoholic beverages are technically soft drinks by this definition but are not generally referred to as such, Soft drinks may be served chilled, over ice cubes or at room temperature. In rare cases, some drinks, such as Dr Pepper. Soft drinks are available in formats, including cans, glass bottles. Soft drinks are widely available at fast food restaurants, movie theaters, convenience stores, casual dining restaurants, dedicated soda stores. Soda fountain drinks are served in paper or plastic disposable cups in the first three venues. In casual dining restaurants and bars, soft drinks are served in glasses. Soft drinks may be drunk with straws or sipped directly from the cups, Soft drinks are mixed with other ingredients in several contexts. In Western countries, in bars and other places where alcohol is served many mixed drinks are made by blending a soft drink with hard liquor, one well-known example is the rum and coke, which may also contain lime juice. Some homemade fruit punch recipes, which may or may not contain alcohol, contain a mixture of fruit juices. At ice cream parlours and 1950s-themed diners, ice cream floats are often sold, two popular ice cream floats are the coke float and the root beer float, which consist of a scoop of ice cream placed in a tall glass of the respectively named soft drinks. Due to the sugar content in typical soft drinks, they may also be called sugary drinks. In Spanish, they use the English equivalent of refreshment, or also commonly called gaseosa. In the United States, the 2003 Harvard Dialect Survey tracked the usage of the nine most common names, over half of the survey respondents preferred the term soda, which was dominant in the Northeastern United States, California, and the areas surrounding Milwaukee and St. Louis. The term tonic is hyperlocal to eastern Massachusetts, although usage is declining, in the English-speaking parts of Canada, the term pop is prevalent, but soft drink is the most common English term used in Montreal. In the United Kingdom and Ireland, the terms fizzy drink, pop and fizzy pop are used in northern England, while mineral is used in Ireland
3.
Mudpot
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A mudpot — or mud pool — is a sort of acidic hot spring, or fumarole, with limited water. It usually takes the form of a pool of bubbling mud, the acid and microorganisms decompose surrounding rock into clay and mud. The mud of a mudpot takes the form of a viscous, often bubbling, as the boiling mud is often squirted over the brims of the mudpot, a sort of mini-volcano of mud starts to build up, sometimes reaching heights of 3–5 feet. Although mudpots are often called mud volcanoes, true mud volcanoes are very different in nature, the mud of a mudpot is generally of white to greyish color, but is sometimes stained with reddish or pink spots from iron compounds. When the slurry is particularly colorful, the feature may be referred to as a paint pot, Mudpots form in high-temperature geothermal areas where water is in short supply. The little water that is available rises to the surface at a spot where the soil is rich in volcanic ash, clay, the thickness of the mud usually changes along with seasonal changes in the water table. The geothermal areas of Yellowstone National Park contain several examples of both mudpots and paint pots, as do some areas of Iceland and New Zealand. Several locations in and around the Salton Sea in California are also home to active mudpots, Mudpots at Yellowstone National Park official site Mudpots photo gallery at Yellowstone NP official site
4.
Tar pit
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A tar pit, or more accurately an asphalt pit or asphalt lake, is the result of a type of petroleum seep where subterranean bitumen leaks to the surface, creating a large area of natural asphalt. This happens because, after the material reaches the surface, its lighter components vaporize, over a million fossils have been found in tar pits around the globe. For other rich deposits, fossilized where they occurred, see Lagerstätten, living bacteria have been found in the La Brea Tar Pits. These organisms have shown to be strains of previously discovered bacteria. They have been able to survive and thrive in an environment with little water, scientists started looking for the bacteria when they noticed bubbles of methane coming out of the tar pits. Other microorganisms have been living in microliter-sized droplets of water recovered from Pitch Lake in Trinidad. Helaeomyia petrolei, the fly, spends its larval stage within the tar pit. Formerly Lake Asphaltitis for the Dead Sea
5.
Liquid
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A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a constant volume independent of pressure. As such, it is one of the four states of matter. A liquid is made up of tiny vibrating particles of matter, such as atoms, water is, by far, the most common liquid on Earth. Like a gas, a liquid is able to flow and take the shape of a container, most liquids resist compression, although others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, a distinctive property of the liquid state is surface tension, leading to wetting phenomena. The density of a liquid is usually close to that of a solid, therefore, liquid and solid are both termed condensed matter. On the other hand, as liquids and gases share the ability to flow, although liquid water is abundant on Earth, this state of matter is actually the least common in the known universe, because liquids require a relatively narrow temperature/pressure range to exist. Most known matter in the universe is in form as interstellar clouds or in plasma form within stars. Liquid is one of the four states of matter, with the others being solid, gas. Unlike a solid, the molecules in a liquid have a greater freedom to move. The forces that bind the molecules together in a solid are only temporary in a liquid, a liquid, like a gas, displays the properties of a fluid. A liquid can flow, assume the shape of a container, if liquid is placed in a bag, it can be squeezed into any shape. These properties make a suitable for applications such as hydraulics. Liquid particles are bound firmly but not rigidly and they are able to move around one another freely, resulting in a limited degree of particle mobility. As the temperature increases, the vibrations of the molecules causes distances between the molecules to increase. When a liquid reaches its point, the cohesive forces that bind the molecules closely together break. If the temperature is decreased, the distances between the molecules become smaller, only two elements are liquid at standard conditions for temperature and pressure, mercury and bromine. Four more elements have melting points slightly above room temperature, francium, caesium, gallium and rubidium, metal alloys that are liquid at room temperature include NaK, a sodium-potassium metal alloy, galinstan, a fusible alloy liquid, and some amalgams
6.
Marangoni effect
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The Marangoni effect is the mass transfer along an interface between two fluids due to surface tension gradient. In the case of temperature dependence, this phenomenon may be called thermo-capillary convection and this phenomenon was first identified in the so-called tears of wine by physicist James Thomson in 1855. The general effect is named after Italian physicist Carlo Marangoni, who studied it for his dissertation at the University of Pavia. A complete theoretical treatment of the subject was given by J. Willard Gibbs in his work On the Equilibrium of Heterogeneous Substances, the surface tension gradient can be caused by concentration gradient or by a temperature gradient. As an example, wine may exhibit an effect called tears. The effect is a consequence of the fact that alcohol has a surface tension than water. If alcohol is mixed with water inhomogeneously, a region with a concentration of alcohol will pull on the surrounding fluid more strongly than a region with a higher alcohol concentration. The result is that the liquid tends to flow away from regions with higher alcohol concentration—along the tension gradient. This can also be demonstrated by spreading a thin film of water on a smooth surface. The liquid will rush out of the region where the drop of alcohol fell, the Marangoni number, a dimensionless value, can be used to characterize the relative effects of surface tension and viscous forces. Many experiments have been conducted under microgravity conditions aboard sounding rockets to observe the Marangoni effect without the influence of gravity and this is due to the very weak Marangoni effect within a mixture of almost identical surface tensions which is normally masked by the fluids inertia due to gravity. A familiar example is in soap films, the Marangoni effect stabilizes soap films, another instance of the Marangoni effect appears in the behavior of convection cells, the so-called Bénard cells. One important application of the Marangoni effect is the use for drying silicon wafers after a wet processing step during the manufacture of integrated circuits, liquid spots left on the wafer surface can cause oxidation that damages components on the wafer. A similar phenomenon has been utilized to self-assemble nanoparticles into ordered arrays. An alcohol containing nanoparticles is spread on the substrate, followed by blowing the substrate with an air flow. The alcohol is evaporated under the flow, simultaneously, water condenses and forms microdroplets on the substrate. Meanwhile, the nanoparticles in alcohol are transferred into the microdroplets, the Marangoni effect is also important to the fields of welding, crystal growth and electron beam melting of metals
7.
Nucleation
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Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly or self-organization. Nucleation is typically defined to be the process that determines how long an observer has to wait before the new phase or self-organized structure appears, nucleation is often found to be very sensitive to impurities in the system. Because of this, it is important to distinguish between heterogeneous nucleation and homogeneous nucleation. Heterogeneous nucleation occurs at sites on surfaces in the system. Homogeneous nucleation occurs away from a surface, nucleation is usually a stochastic process, so even in two identical systems nucleation will occur at different times. This behaviour is similar to radioactive decay, a common mechanism is illustrated in the animation to the right. This shows nucleation of a new phase in an existing phase and this nucleus of the red phase then grows and converts the system to this phase. The standard theory that describes this behaviour for the nucleation of a new phase is called classical nucleation theory. This is seen for example in the nucleation of ice in supercooled water droplets. The decay rate of the exponential gives the nucleation rate, classical nucleation theory is a widely used approximate theory for estimating these rates, and how they vary with variables such as temperature. It correctly predicts that the time you have to wait for nucleation decreases extremely rapidly when supersaturated and it is not just new phases such as liquids and crystals that form via nucleation followed by growth. The self-assembly process that forms objects like the amyloid aggregates associated with Alzheimers disease also starts with nucleation, energy consuming self-organising systems such as the microtubules in cells also show nucleation and growth. Clouds form when wet air cools and many small water droplets nucleate from the supersaturated air, the amount of water vapor that air can carry decreases with lower temperatures. The excess vapor begins to nucleate and to small water droplets which form a cloud. Nucleation of the droplets of water is heterogeneous, occurring on particles referred to as cloud condensation nuclei. Cloud seeding is the process of adding artificial condensation nuclei to quicken the formation of clouds, nucleation is the first step in crystallisation, so it determines if a crystal can form. Frequently crystals do not form even when they are thermodynamically the favored state, for example, small droplets of very pure water can remain liquid down to below -30 °C although ice is the stable state below 0 °C. Bubbles of carbon dioxide nucleate shortly after the pressure is released from a container of carbonated liquid, nucleation often occurs more easily at a pre-existing interface, as happens on boiling chips and on string used to make rock candy
8.
Water vapor
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Water vapor, water vapour or aqueous vapor, is the gaseous phase of water. It is one state of water within the hydrosphere, water vapor can be produced from the evaporation or boiling of liquid water or from the sublimation of ice. Unlike other forms of water, water vapor is invisible, under typical atmospheric conditions, water vapor is continuously generated by evaporation and removed by condensation. It is lighter than air and triggers convection currents that can lead to clouds, use of water vapor, as steam, has been important to humans for cooking and as a major component in energy production and transport systems since the industrial revolution. Likewise the detection of water vapor would indicate a similar distribution in other planetary systems. Water vapor is significant in that it can be evidence supporting the presence of extraterrestrial liquid water in the case of some planetary mass objects. Whenever a water molecule leaves a surface and diffuses into a surrounding gas, each individual water molecule which transitions between a more associated and a less associated state does so through the absorption or release of kinetic energy. The aggregate measurement of kinetic energy transfer is defined as thermal energy. Liquid water that becomes water vapor takes a parcel of heat with it, the amount of water vapor in the air determines how fast each molecule will return to the surface. When a net evaporation occurs, the body of water will undergo a net cooling directly related to the loss of water, in the US, the National Weather Service measures the actual rate of evaporation from a standardized pan open water surface outdoors, at various locations nationwide. Others do likewise around the world, the US data is collected and compiled into an annual evaporation map. The measurements range from under 30 to over 120 inches per year, formulas can be used for calculating the rate of evaporation from a water surface such as a swimming pool. In some countries, the evaporation rate far exceeds the precipitation rate, evaporative cooling is restricted by atmospheric conditions. Humidity is the amount of vapor in the air. The vapor content of air is measured with devices known as hygrometers, the measurements are usually expressed as specific humidity or percent relative humidity. This condition is referred to as complete saturation. Humidity ranges from 0 gram per cubic metre in dry air to 30 grams per cubic metre when the vapor is saturated at 30 °C, another form of evaporation is sublimation, by which water molecules become gaseous directly, leaving the surface of ice without first becoming liquid water. Sublimation accounts for the slow disappearance of ice and snow at temperatures too low to cause melting
9.
Atmosphere of Earth
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The atmosphere of Earth is the layer of gases, commonly known as air, that surrounds the planet Earth and is retained by Earths gravity. The atmosphere of Earth protects life on Earth by absorbing solar radiation, warming the surface through heat retention. By volume, dry air contains 78. 09% nitrogen,20. 95% oxygen,0. 93% argon,0. 04% carbon dioxide, and small amounts of other gases. Air also contains an amount of water vapor, on average around 1% at sea level. The atmosphere has a mass of about 5. 15×1018 kg, the atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km, or 1. 57% of Earths radius, is used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km, several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition. The study of Earths atmosphere and its processes is called atmospheric science, early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann. The three major constituents of air, and therefore of Earths atmosphere, are nitrogen, oxygen, water vapor accounts for roughly 0. 25% of the atmosphere by mass. The remaining gases are often referred to as gases, among which are the greenhouse gases, principally carbon dioxide, methane, nitrous oxide. Filtered air includes trace amounts of other chemical compounds. Various industrial pollutants also may be present as gases or aerosols, such as chlorine, fluorine compounds, sulfur compounds such as hydrogen sulfide and sulfur dioxide may be derived from natural sources or from industrial air pollution. In general, air pressure and density decrease with altitude in the atmosphere, however, temperature has a more complicated profile with altitude, and may remain relatively constant or even increase with altitude in some regions. In this way, Earths atmosphere can be divided into five main layers, excluding the exosphere, Earth has four primary layers, which are the troposphere, stratosphere, mesosphere, and thermosphere. It extends from the exobase, which is located at the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km where it merges into the solar wind. This layer is composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another, thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may migrate in and out of the magnetosphere or the solar wind, the exosphere is located too far above Earth for any meteorological phenomena to be possible
10.
Sea foam
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These compounds can act as surfactants or foaming agents. Due to its low density and persistence, foam can be blown by strong winds from the beachface inland. Where polluted stormwater from rivers or drains discharges to the coast, sea foam formed on adjacent beaches can be polluted with viruses and other contaminants, and may have an unpleasant odour. A large buildup of sea foam occurred on the coast of Yamba, northern New South Wales, 29°26′S 153°21′E on 24 August 2007, during live coverage of Hurricane Irene in Ocean City, Maryland, Tucker Barnes was covered in sea foam. In December 2011, the coast road at Cleveleys, Lancashire was swamped by metre high drifts of sea foam, following storms and high winds on 24/25 September 2012, the beach front of the Footdee area of Aberdeen was engulfed with sea foam. Between 27 and 28 January 2013, the Sunshine Coast in Queensland, Foam lines Spume Island April 2007 Storm Photo Gallery Lane Memorial Library, Hampton, New Hampshire. Accessed 5 November 2010 How foam forms on ocean waves Newscientist. com, accessed 5 November 2010 Blanket of white foam covers Aberdeen coast - Guardian video. Accessed 25 September 2012 Sea Foam Video on YouTube Sea foam covering a swimmer, Australia Gold Coast
11.
Soap bubble
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A soap bubble is an extremely thin film of soapy water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting and they are often used for childrens enjoyment, but they are also used in artistic performances. Assembling several bubbles results in a foam, when light shines onto a bubble it appears to change colour. Depending on the thickness of the film, different colours interfere constructively and destructively, Soap bubbles are physical examples of the complex mathematical problem of minimal surface. They will assume the shape of least surface area possible containing a given volume, a true minimal surface is more properly illustrated by a soap film, which has equal pressure on inside as outside, hence is a surface with zero mean curvature. A soap bubble is a soap film, due to the difference in outside and inside pressure. This has been dubbed the double bubble conjecture, due to these qualities soap bubbles films have been used with practical problem solving application. A famous example is his West German Pavilion at Expo 67 in Montreal, when two bubbles merge, they adopt a shape which makes the sum of their surface areas as small as possible, compatible with the volume of air each bubble encloses. If the bubbles are of size, their common wall is flat. If they arent the same size, their common wall bulges into the bubble, since the smaller one has a higher internal pressure than the larger one. At a point where three or more bubbles meet, they sort themselves out so only three bubble walls meet along a line. Since the surface tension is the same in each of the three surfaces, the three angles between them must be equal to 120°, only four bubble walls can meet at a point, with the lines where triplets of bubble walls meet separated by cos−1 ≈109. 47°. All these rules, known as Plateaus laws, determine how a foam is built from bubbles, the longevity of a soap bubble is limited by the ease of rupture of the very thin layer of water which constitutes its surface, namely a micrometer-thick soap film. It is thus sensitive to, Drainage within the soap film and this can be slowed down by increasing the water viscosity, for instance by adding glycerol. Still, there is a height limit, which is the capillary length, very high for soap bubbles. In principle, there is no limit in the length it can reach, evaporation, This can be slowed down by blowing bubbles in a wet atmosphere, or by adding some sugar to the water. Dirt and fat, When the bubble touches the ground, a wall, or our skin and this can be prevented by wetting these surfaces with water. When a soap bubble is in contact with a solid or a liquid surface wetting is observed, on a solid surface, the contact angle of the bubble depends on the surface energy of the solid
12.
Glass
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Glass is a non-crystalline amorphous solid that is often transparent and has widespread practical, technological, and decorative usage in, for example, window panes, tableware, and optoelectronics. The most familiar, and historically the oldest, types of glass are silicate glasses based on the chemical compound silica, the primary constituent of sand. The term glass, in usage, is often used to refer only to this type of material. Many applications of silicate glasses derive from their optical transparency, giving rise to their use as window panes. Glass can be coloured by adding metallic salts, and can also be painted and printed with vitreous enamels and these qualities have led to the extensive use of glass in the manufacture of art objects and in particular, stained glass windows. Although brittle, silicate glass is extremely durable, and many examples of glass fragments exist from early glass-making cultures, because glass can be formed or moulded into any shape, it has been traditionally used for vessels, bowls, vases, bottles, jars and drinking glasses. In its most solid forms it has also used for paperweights, marbles. Some objects historically were so commonly made of glass that they are simply called by the name of the material, such as drinking glasses. Porcelains and many polymer thermoplastics familiar from everyday use are glasses and these sorts of glasses can be made of quite different kinds of materials than silica, metallic alloys, ionic melts, aqueous solutions, molecular liquids, and polymers. For many applications, like glass bottles or eyewear, polymer glasses are a lighter alternative than traditional glass, silica is a common fundamental constituent of glass. In nature, vitrification of quartz occurs when lightning strikes sand, forming hollow, fused quartz is a glass made from chemically-pure SiO2. It has excellent resistance to shock, being able to survive immersion in water while red hot. However, its high melting-temperature and viscosity make it difficult to work with, normally, other substances are added to simplify processing. One is sodium carbonate, which lowers the transition temperature. The soda makes the glass water-soluble, which is undesirable, so lime, some magnesium oxide. The resulting glass contains about 70 to 74% silica by weight and is called a soda-lime glass, soda-lime glasses account for about 90% of manufactured glass. Most common glass contains other ingredients to change its properties, lead glass or flint glass is more brilliant because the increased refractive index causes noticeably more specular reflection and increased optical dispersion. Adding barium also increases the refractive index, iron can be incorporated into glass to absorb infrared energy, for example in heat absorbing filters for movie projectors, while cerium oxide can be used for glass that absorbs UV wavelengths
13.
Spirit level
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A spirit level, bubble level or simply a level is an instrument designed to indicate whether a surface is horizontal or vertical. Early spirit levels had very slightly curved glass vials with constant inner diameter at each viewing point and these vials are incompletely filled with a liquid, usually a colored spirit or alcohol, leaving a bubble in the tube. They have an upward curve, so that the bubble naturally rests in the center. At slight inclinations the bubble travels away from the center position. Where a spirit level must also be usable upside-down or on its side, alcohols such as ethanol are often used rather than water. Alcohols have low viscosity and surface tension, which allows the bubble to travel the tube quickly, alcohols also have a much wider liquid temperature range, and wont break the vial as water could due to ice expansion. A colorant such as fluorescein, typically yellow or green, may be added to increase the visibility of the bubble. An extension of the level is the bulls eye level. It serves to level a surface across a plane, while the level only does so in the direction of the tube. To check the accuracy of a carpenters type level, a horizontal surface is not needed. The level is placed on a flat and roughly level surface and this reading indicates to what extent the surface is parallel to the horizontal plane, according to the level, which at this stage is of unknown accuracy. The spirit level is then rotated through 180 degrees in the horizontal plane, if the level is accurate, it will indicate the same orientation with respect to the horizontal plane. A difference implies that the level is inaccurate, a similar procedure is applied to more sophisticated instruments such as a surveyors level or a theodolite and is a matter of course each time the instrument is set up. In this latter case, the plane of rotation of the instrument is levelled and this is done in two horizontal perpendicular directions. The sensitivity is an important specification for a level, its accuracy depends on its sensitivity. The sensitivity of a level is given as the change of angle or gradient required to move the bubble by unit distance, if the bubble housing has graduated divisions then the sensitivity is the angle or gradient change that moves the bubble by one of these divisions. 2 mm is the spacing for graduations, on a surveyors level the bubble will move 2 mm when the vial is tilted about 0.005 degree. For a precision machinist level with 2mm divisions, when the vial is tilted 5 arc seconds the bubble will move one graduation and this is equivalent to movement of.0005 inches measured one foot from the pivot point, referred to as 5 ten-thousandths per foot
14.
Refractive index
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In optics, the refractive index or index of refraction n of a material is a dimensionless number that describes how light propagates through that medium. It is defined as n = c v, where c is the speed of light in vacuum, for example, the refractive index of water is 1.333, meaning that light travels 1.333 times faster in a vacuum than it does in water. The refractive index determines how light is bent, or refracted. The refractive indices also determine the amount of light that is reflected when reaching the interface, as well as the angle for total internal reflection. This implies that vacuum has a index of 1. The refractive index varies with the wavelength of light and this is called dispersion and causes the splitting of white light into its constituent colors in prisms and rainbows, and chromatic aberration in lenses. Light propagation in absorbing materials can be described using a refractive index. The imaginary part then handles the attenuation, while the real part accounts for refraction, the concept of refractive index is widely used within the full electromagnetic spectrum, from X-rays to radio waves. It can also be used with wave phenomena such as sound, in this case the speed of sound is used instead of that of light and a reference medium other than vacuum must be chosen. Thomas Young was presumably the person who first used, and invented, at the same time he changed this value of refractive power into a single number, instead of the traditional ratio of two numbers. The ratio had the disadvantage of different appearances, newton, who called it the proportion of the sines of incidence and refraction, wrote it as a ratio of two numbers, like 529 to 396. Hauksbee, who called it the ratio of refraction, wrote it as a ratio with a fixed numerator, hutton wrote it as a ratio with a fixed denominator, like 1.3358 to 1. Young did not use a symbol for the index of refraction, in the next years, others started using different symbols, n, m, and µ. For visible light most transparent media have refractive indices between 1 and 2, a few examples are given in the adjacent table. These values are measured at the yellow doublet D-line of sodium, with a wavelength of 589 nanometers, gases at atmospheric pressure have refractive indices close to 1 because of their low density. Almost all solids and liquids have refractive indices above 1.3, aerogel is a very low density solid that can be produced with refractive index in the range from 1.002 to 1.265. Moissanite lies at the end of the range with a refractive index as high as 2.65. Most plastics have refractive indices in the range from 1.3 to 1.7, for infrared light refractive indices can be considerably higher
15.
Snell's law
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In optics, the law is used in ray tracing to compute the angles of incidence or refraction, and in experimental optics to find the refractive index of a material. The law is also satisfied in metamaterials, which light to be bent backward at a negative angle of refraction with a negative refractive index. Although named after Dutch astronomer Willebrord Snellius, the law was first accurately described by the scientist Ibn Sahl at the Baghdad court in 984, in the manuscript On Burning Mirrors and Lenses, Sahl used the law to derive lens shapes that focus light with no geometric aberrations. The law follows from Fermats principle of least time, which in turn follows from the propagation of light as waves, ptolemy, a Greek living in Alexandria, Egypt, had found a relationship regarding refraction angles, but it was inaccurate for angles that were not small. Ptolemy was confident he had found an empirical law, partially as a result of fudging his data to fit theory. Alhazen, in his Book of Optics, came closer to discovering the law of refraction, although named after Dutch astronomer Willebrord Snellius, the law was first accurately described by the Persian scientist Ibn Sahl at the Baghdad court in 984. In the manuscript On Burning Mirrors and Lenses, Sahl used the law to derive lens shapes that focus light with no geometric aberrations. The law was rediscovered by Thomas Harriot in 1602, who however did not publish his results although he had corresponded with Kepler on this very subject, in 1621, Willebrord Snellius derived a mathematically equivalent form, that remained unpublished during his lifetime. René Descartes independently derived the law using heuristic momentum conservation arguments in terms of sines in his 1637 essay Dioptrics, rejecting Descartes solution, Pierre de Fermat arrived at the same solution based solely on his principle of least time. Interestingly, Descartes assumed the speed of light was infinite, yet in his derivation of Snells law he also assumed the denser the medium, the greater the speed of light. Fermat supported the assumptions, i. e. the speed of light is finite. Fermats derivation also utilized his invention of adequality, a mathematical equivalent to differential calculus, for finding maxima, minima. In his influential mathematics book Geometry, Descartes solves a problem that was worked on by Apollonius of Perga, given n lines L and a point P on each line, find the locus of points Q such that the lengths of the line segments QP satisfy certain conditions. For example, when n =4, given the lines a, b, c, and d and a point A on a, B on b, and so on, find the locus of points Q such that the product QA*QB equals the product QC*QD. When the lines are not all parallel, Pappus showed that the loci are conics, to show that the cubic curves were interesting, he showed that they arose naturally in optics from Snells law. According to Dijksterhuis, In De natura lucis et proprietate Isaac Vossius said that Descartes had seen Snells paper and we now know this charge to be undeserved but it has been adopted many times since. Both Fermat and Huygens repeated this accusation that Descartes had copied Snell, in French, Snells Law is called la loi de Descartes or loi de Snell-Descartes. As the development of optical and electromagnetic theory, the ancient Snells law was brought into a new stage
16.
Refraction
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Refraction is the change in direction of wave propagation due to a change in its transmission medium. The phenomenon is explained by the conservation of energy and the conservation of momentum, due to the change of medium, the phase velocity of the wave is changed but its frequency remains constant. This is most commonly observed when a wave passes from one medium to another at any other than 0° from the normal. In optics, refraction is a phenomenon that occurs when waves travel from a medium with a given refractive index to a medium with another at an oblique angle. At the boundary between the media, the phase velocity is altered, usually causing a change in direction. Its wavelength increases or decreases, but its frequency remains constant, for example, a light ray will refract as it enters and leaves glass, assuming there is a change in refractive index. A ray traveling along the normal will change speed, but not direction, refraction still occurs in this case. Understanding of this led to the invention of lenses and the refracting telescope. Refraction can be seen looking into a bowl of water. Air has a index of about 1.0003. If a person looks at an object, such as a pencil or straw, which is placed at a slant, partially in the water. This is due to the bending of light rays as they move from the water to the air, once the rays reach the eye, the eye traces them back as straight lines. The lines of sight intersect at a position than where the actual rays originated. This causes the pencil to appear higher and the water to appear shallower than it really is, the depth that the water appears to be when viewed from above is known as the apparent depth. This is an important consideration for spearfishing from the surface because it will make the fish appear to be in a different place. Conversely, an object above the water has a higher apparent height when viewed from below the water, the opposite correction must be made by an archer fish. For small angles of incidence, the ratio of apparent to real depth is the ratio of the indexes of air to that of water. But, as the angle of incidence approaches 90o, the apparent depth approaches zero, albeit reflection increases, the diagram on the right shows an example of refraction in water waves
17.
Total internal reflection
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Total internal reflection is the phenomenon which occurs when a propagated wave strikes a medium boundary at an angle larger than a particular critical angle with respect to the normal to the surface. If the refractive index is lower on the side of the boundary and the incident angle is greater than the critical angle. The critical angle is the angle of incidence above which the internal reflection occurs. This is particularly common as a phenomenon, where light waves are involved. When a wave reaches a boundary between different materials with different refractive indices, the wave will in general be partially refracted at the boundary surface, and partially reflected. This can only occur when the wave in a medium with a refractive index reaches a boundary with a medium of lower refractive index. For example, it will occur with light reaching air from glass, Total internal reflection of light can be demonstrated using a semi-circular block of glass or plastic. A ray box shines a beam of light onto the glass medium. At the glass/air boundary of the surface, what happens will depend on the angle. If θc is the angle, then the following scenarios depict what will happen according to the size of the incident angle. If θ ≤ θc, the ray will split, some of the ray will reflect off the boundary and this is not total internal reflection. If θ > θc, the ray reflects from the boundary. This is called total internal reflection and this physical property makes optical fibers useful and prismatic binoculars possible. It is also what gives diamonds their distinctive sparkle, as diamond has a high refractive index. The critical angle is the angle of incidence for which the angle of refraction is 90°, the angle of incidence is measured with respect to the normal at the refractive boundary. Consider a light ray passing from glass into air, the light emanating from the interface is bent towards the glass. When the incident angle is increased sufficiently, the transmitted angle reaches 90 degrees and it is at this point no light is transmitted into air. The critical angle θ c is given by Snells law, n 1 sin θ i = n 2 sin θ t, rearranging Snells Law, we get incidence sin θ i = n 2 n 1 sin θ t
18.
Thin-film interference
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When the thickness of the film is an odd multiple of one quarter-wavelength of the light on it, the reflected waves from both surfaces interfere to cancel each other. Since the wave cannot be reflected, it is transmitted instead. When the thickness is a multiple of a half-wavelength of the light, thus when white light, which consists of a range of wavelengths, is incident on the film, certain wavelengths are intensified while others are attenuated. Thin-film interference explains the colors seen in light reflected from soap bubbles. It also is the mechanism behind the action of antireflection coatings used on glasses, studying the light reflected or transmitted by a thin film can reveal information about the thickness of the film or the effective refractive index of the film medium. Thin films have many applications including anti-reflection coatings, mirrors. A thin film is a layer of material thickness in the sub-nanometer to micron range. As light strikes the surface of a film it is transmitted or reflected at the upper surface. Light that is transmitted reaches the surface and may once again be transmitted or reflected. The Fresnel equations provide a description of how much of the light will be transmitted or reflected at an interface. The light reflected from the upper and lower surfaces will interfere, the degree of constructive or destructive interference between the two light waves depends on the difference in their phase. This difference in turn depends on the thickness of the layer, the refractive index of the film. Additionally, a shift of 180° or π radians may be introduced upon reflection at a boundary depending on the refractive indices of the materials on either side of the boundary. This phase shift occurs if the index of the medium the light is travelling through is less than the refractive index of the material it is striking. In other words, if n 1 < n 2 and the light is travelling from material 1 to material 2, the pattern of light that results from this interference can appear either as light and dark bands or as colorful bands depending upon the source of the incident light. Consider light incident on a film and reflected by both the upper and lower boundaries. The optical path difference of the light must be calculated in order to determine the condition for interference. 2 n 2 d cos = m λ This condition may change after considering possible phase shifts occur upon reflection
19.
Specular reflection
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Specular reflection, also known as regular reflection is the mirror-like reflection of waves, such as light, from a surface. In this process, each incident ray is reflected, with the reflected ray having the same angle to the normal as the incident ray. The result is that an image reflected by the surface is reproduced in mirror-like fashion, the law of reflection states that for each incident ray the angle of incidence equals the angle of reflection, and the incident, normal, and reflected directions are coplanar. This behavior was first described by Hero of Alexandria, when light hits a surface, there are three possible outcomes. Light may be absorbed by the material, light may be transmitted through the surface, or light may be reflected back. Materials often show some mix of these behaviors, with the proportion of light that goes to each depending on the properties of the material, the wavelength of the light, and the angle of incidence. For most interfaces between materials, the fraction of the light that is reflected increases with increasing angle of incidence θ i, reflected light can be divided into two sub-types, specular reflection and diffuse reflection. Specular reflection reflects all light at the angle, whereas diffuse reflection reflects in a broad range of directions. An example of the distinction between specular and diffuse reflection would be glossy and matte paints, matte paints have almost exclusively diffuse reflection, while glossy paints have both specular and diffuse reflection. A surface built from a powder, such as plaster, can be a nearly perfect diffuser. The reflecting material of mirrors is usually aluminum or silver, the law of reflection describes the angle of reflected light, the angle of incident light is the same as the angle of the reflected light. If a mirror becomes very small compared to the wavelength, the law of reflection no longer holds, the law of reflection can also be equivalently expressed using linear algebra. The direction of a ray is determined by the vector of incidence. Different authors may define the incident and reflection directions with different signs, reflectivity is the ratio of the power of the reflected wave to that of the incident wave. It is a function of the wavelength of radiation, and is related to the index of the material as expressed by Fresnels equations. The polarization of the light depends on the symmetry of the arrangement of the incident probing light with respect to the absorbing transitions dipole moments in the material. Measurement of specular reflection is performed with normal or varying incidence reflection spectrophotometers using a scanning variable-wavelength light source, lower quality measurements using a glossmeter quantify the glossy appearance of a surface in gloss units. Specular reflection from a dielectric such as water can affect polarization, the image in a flat mirror has these features, It is the same distance behind the mirror as the object is in front
20.
Bubblegram
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A bubblegram is a solid block of glass or transparent plastic that has been exposed to laser beams to generate three-dimensional designs inside. The image is composed of many points of fracture or other visible deformations. Each point is created by a beam focused to high intensity at that location by a computer-controlled opto-mechanical system. A complex or highly detailed image occupying a 5 cm cubic volume typically requires the creation of tens of thousands of such points, there also exist companies which will take custom photographs of people, convert them to a heightmap, then render that as a bubblegram memento. List of laser articles Volumetric display Laser Crystal Technique How a single laser beam makes a bubblegram
21.
Ultrasound
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Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is no different from normal sound in its physical properties and this limit varies from person to person and is approximately 20 kilohertz in healthy, young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz, Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances, Ultrasound imaging or sonography is often used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws, industrially, ultrasound is used for cleaning, mixing, and to accelerate chemical processes. Animals such as bats and porpoises use ultrasound for locating prey, scientist are also studying ultrasound using graphene diaphragms as a method of communication. Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound and not vision. The first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917, the piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water. Ultrasound is defined by the American National Standards Institute as sound at frequencies greater than 20 kHz, in air at atmospheric pressure ultrasonic waves have wavelengths of 1.9 cm or less. The upper frequency limit in humans is due to limitations of the middle ear, auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear. Children can hear some high-pitched sounds that older adults cannot hear, the Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people. Bats use a variety of ultrasonic ranging techniques to detect their prey and they can detect frequencies beyond 100 kHz, possibly up to 200 kHz. Many insects have good hearing and most of these are nocturnal insects listening for echolocating bats. This includes many groups of moths, beetles, praying mantids, upon hearing a bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger an action in the noctuid moth that cause it to drop slightly in its flight to evade attack. Tiger moths also emit clicks which may disturb bats echolocation, dogs and cats hearing range extends into the ultrasound, the top end of a dogs hearing range is about 45 kHz, while a cats is 64 kHz. The wild ancestors of cats and dogs evolved this higher hearing range to hear sounds made by their preferred prey. A dog whistle is a whistle that emits ultrasound, used for training and calling dogs, porpoises have the highest known upper hearing limit, at around 160 kHz
22.
Inkjet printing
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Inkjet printing is a type of computer printing that recreates a digital image by propelling droplets of ink onto paper, plastic, or other substrates. Inkjet printers are the most commonly used type of printer, the concept of inkjet printing originated in the 20th century, and the technology was first extensively developed in the early 1950s. Starting in the late 1970s inkjet printers that could reproduce digital images generated by computers were developed, mainly by Epson, Hewlett-Packard, in the worldwide consumer market, four manufacturers account for the majority of inkjet printer sales, Canon, HP, Epson, and Brother. The emerging ink jet material deposition market also uses inkjet technologies, typically printheads using piezoelectric crystals, the technology has been extended and the ″ink″ can now also comprise living cells, for creating biosensors and for tissue engineering. There are two main technologies in use in contemporary inkjet printers, continuous and Drop-on-demand, the continuous inkjet method is used commercially for marking and coding of products and packages. In 1867 Lord Kelvin patented the syphon recorder, which recorded telegraph signals as a trace on paper using an ink jet nozzle deflected by a magnetic coil. The first commercial devices were introduced in 1951 by Siemens, the ink droplets are subjected to an electrostatic field created by a charging electrode as they form, the field varies according to the degree of drop deflection desired. This results in a controlled, variable electrostatic charge on each droplet, charged droplets are separated by one or more uncharged guard droplets to minimize electrostatic repulsion between neighbouring droplets. The more highly charged droplets are deflected to a greater degree, only a small fraction of the droplets is used to print, the majority being recycled. CIJ is one of the oldest ink jet technologies in use and is fairly mature, viscosity is monitored and a solvent is added to counteract solvent loss. Drop-on-demand is divided into thermal DOD and piezoelectric DOD, most consumer inkjet printers, including those from Canon, Hewlett-Packard, and Lexmark, use the thermal inkjet process. Vaughts work started in late 1978 with a project to develop fast, low-cost printing, the team at HP found that thin-film resistors could produce enough heat to fire an ink droplet. Two years later the HP and Canon teams found out about each others work, in the thermal inkjet process, the print cartridges consist of a series of tiny chambers, each containing a heater, all of which are constructed by photolithography. The inks involved are usually water-based and use either pigments or dyes as the colorant, the inks must have a volatile component to form the vapor bubble, otherwise droplet ejection cannot occur. As no special materials are required, the print head is generally cheaper to produce than in other inkjet technologies, most commercial and industrial inkjet printers and some consumer printers use a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element. When a voltage is applied, the material changes shape, generating a pressure pulse in the fluid. A DOD process uses software that directs the heads to apply between zero and eight droplets of ink per dot, only where needed, piezo inkjet technology is often used on production lines to mark products. For instance, the date is often applied to products with this technique, in this application the head is stationary
23.
Microfluidics
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Microfluidics deals with the behaviour, precise control and manipulation of fluids that are geometrically constrained to a small, typically sub-millimeter, scale. Microfluidics emerged in the beginning of the 1980s and is used in the development of inkjet printheads, DNA chips, lab-on-a-chip technology, micro-propulsion, and micro-thermal technologies. Typically, micro means one of the features, small volumes small size low energy consumption effects of the microdomain Typically fluids are moved, mixed, separated or otherwise processed. Numerous applications employ passive fluid control techniques like capillary forces, in some applications, external actuation means are additionally used for a directed transport of the media. Examples are rotary drives applying centrifugal forces for the transport on the passive chips. Active microfluidics refers to the manipulation of the working fluid by active components such as micropumps or microvalves. Micropumps supply fluids in a manner or are used for dosing. Microvalves determine the direction or the mode of movement of pumped liquids. Often processes which are carried out in a lab are miniaturised on a single chip in order to enhance efficiency and mobility as well as reducing sample. The behaviour of fluids at the microscale can differ from macrofluidic behaviour in that such as surface tension, energy dissipation. Microfluidics studies how these behaviours change, and how they can be worked around, at small scales some interesting and sometimes unintuitive properties appear. In particular, the Reynolds number can become very low, high specificity of chemical and physical properties can also be ensured resulting in more uniform reaction conditions and higher grade products in single and multi-step reactions. Microfluidic structures include micropneumatic systems, i. e. microsystems for the handling of off-chip fluids, to date, the most successful commercial application of microfluidics is the inkjet printhead. Additionally, advances in microfluidic manufacturing allow the devices to be produced in low-cost plastics, Advances in microfluidics technology are revolutionizing molecular biology procedures for enzymatic analysis, DNA analysis, and proteomics. The basic idea of microfluidic biochips is to integrate assay operations such as detection, as well as sample pre-treatment, an emerging application area for biochips is clinical pathology, especially the immediate point-of-care diagnosis of diseases. Microfluidic technology has led to the creation of tools for biologists to control the complete cellular environment, leading to new questions. In a heterogeneous environment, it is easier for a microorganism to evolve and this can be useful for testing the acceleration of evolution of a microorganism / for testing the development of antibiotic resistance. Some of these areas are further elaborated in the sections below and these technologies are based on the manipulation of continuous liquid flow through microfabricated channels
24.
Cavitation
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Cavitation is the formation of vapour cavities in a liquid – i. e. small liquid-free zones – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to pressure, the voids implode and can generate an intense shock wave. Cavitation is a significant cause of wear in some engineering contexts, collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal causing a type of wear also called cavitation, the most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs. Cavitation is usually divided into two classes of behavior, inertial cavitation and non-inertial cavitation, inertial cavitation is the process where a void or bubble in a liquid rapidly collapses, producing a shock wave. Inertial cavitation occurs in nature in the strikes of mantis shrimps and pistol shrimps, in man-made objects, it can occur in control valves, pumps, propellers and impellers. Non-inertial cavitation is the process in which a bubble in a fluid is forced to oscillate in size or shape due to form of energy input. Such cavitation is often employed in ultrasonic cleaning baths and can also be observed in pumps, propellers, since the shock waves formed by collapse of the voids are strong enough to cause significant damage to moving parts, cavitation is usually an undesirable phenomenon. It is very often specifically avoided in the design of such as turbines or propellers. However, it is useful and does not cause damage when the bubbles collapse away from machinery. Inertial cavitation was first studied by Lord Rayleigh in the late 19th century, when a volume of liquid is subjected to a sufficiently low pressure, it may rupture and form a cavity. This phenomenon is coined cavitation inception and may occur behind the blade of a rotating propeller or on any surface vibrating in the liquid with sufficient amplitude. A fast-flowing river can cause cavitation on rock surfaces, particularly there is a drop-off. Other ways of generating cavitation voids involve the local deposition of energy, vapor gases evaporate into the cavity from the surrounding medium, thus, the cavity is not a perfect vacuum, but has a relatively low gas pressure. Such a low-pressure bubble in a liquid begins to collapse due to the pressure of the surrounding medium. As the bubble collapses, the pressure and temperature of the vapor within increases, at the point of total collapse, the temperature of the vapor within the bubble may be several thousand kelvin, and the pressure several hundred atmospheres. Inertial cavitation can occur in the presence of an acoustic field
25.
Bazooka
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Bazooka is the common name for a man-portable recoilless anti-tank rocket launcher weapon, widely fielded by the United States Army. Also referred to as the Stovepipe, the bazooka was among the first generation of rocket-propelled anti-tank weapons used in infantry combat. Near the end of the war, the Japanese developed a weapon, the Type 470 mm AT Rocket Launcher. The term bazooka still sees use as a generic term referring to any ground-to-ground shoulder-fired missile weapon. The development of the bazooka involved the development of two lines of technology, the rocket-powered weapon, and the shaped-charge warhead. It was also designed for easy maneuverability and access, the rocket-powered weapon was the brainchild of Dr. Robert H. Goddard as a side project of his work on rocket propulsion. He and his co-worker, Dr. Clarence N, the delay in the development of the bazooka was as a result of Goddards serious bout with tuberculosis. Goddard continued to be a consultant to the US government at Indian Head, Maryland, until 1923. Hickman later became head of the National Defense Research Committee in the 1940s where he guided rocket development for the war effort, including completing the development of the bazooka. Shaped charge technology was developed in the US into a shaped charge hand grenade for use by infantry, the grenade was standardized as the M10. However, the M10 grenade weighed 3.5 lb, was difficult to throw by hand, the only practical way to use the weapon was for an infantryman to place it directly on the tank, an unlikely means of delivery in most combat situations. A smaller, less powerful version of the M10, the M9, was then developed and this resulted in the creation of a series of rifle grenade launchers, the M1, the M2, the M7, and the M8. The combination of motor and shaped charge warhead would lead to Army development of light antitank weapons. In 1942, U. S. Army Colonel Leslie Skinner received the M10 shaped-charge grenade which was capable of stopping German tanks and he gave Lieutenant Edward Uhl the task of creating a delivery system for the grenade. Uhl created a small rocket, but needed to protect the firer from the rocket exhaust, according to Uhl, I was walking by this scrap pile, and there was a tube that. Happened to be the size as the grenade that we were turning into a rocket. Put the tube on a shoulder with the rocket inside. By late 1942, the improved Rocket Launcher, M1A1 was introduced, the forward hand grip was deleted, and the design simplified
26.
Torpedo
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Historically, it was called an automotive, automobile, locomotive or fish torpedo, colloquially called a fish. The term torpedo was originally employed for a variety of devices, from about 1900, torpedo has been used strictly to designate an underwater self-propelled weapon. Todays torpedoes can be divided into lightweight and heavyweight classes, and into straight-running, autonomous homers and they can be launched from a variety of platforms. The word torpedo comes from the name of a genus of rays in the order Torpediniformes. In naval usage, the American Robert Fulton introduced the name to refer to a gunpowder charge used by his French submarine Nautilus to demonstrate that it could sink warships. The concept of a torpedo existed many centuries before it was successfully developed. In 1275, Hasan al-Rammah described. an egg which moves itself, in modern language, a torpedo is an underwater self-propelled explosive, —but historically, the term also applied to primitive naval mines. These were used on an ad hoc basis during the modern period up to the late 19th century. An early submarine, the Turtle, attempted to lay a bomb with a fuse on the hull of HMS Eagle during the American Revolutionary War. In the early 1800s, the American inventor Robert Fulton, while in France and he coined the term torpedo in reference to the explosive charges he outfitted his submarine Nautilus. However, both the French and the Dutch governments were uninterested in the submarine, Fulton then concentrated on developing the torpedo independent of a submarine deployment. However, the British government refused to purchase the invention, stating they did not wish to introduce into naval warfare a system that would give advantage to weaker maritime nations. Fulton carried out a demonstration for the US government on 20 July 1807. Further development languished as Fulton focused on his steam-boat matters, during the War of 1812, torpedoes were employed in attempts to destroy British vessels and protect American harbors. In fact a submarine deployed torpedo was used in an attempt to destroy HMS Ramillies while in New Londons harbor. Hardy to warn the Americans to cease efforts with the use of any boat in this cruel and unheard-of warfare. Torpedoes were used by the Russian Empire during the Crimean War in 1855 against British warships in the Gulf of Finland and they used an early form of chemical detonator. During the American Civil War, the torpedo was used for what is today called a contact mine
27.
Alpheidae
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Alpheidae is a family of caridean snapping shrimp characterized by having asymmetrical claws, the larger of which is typically capable of producing a loud snapping sound. Other common names for animals in the group are pistol shrimp or alpheid shrimp, the family is diverse and worldwide in distribution, consisting of about 1119 species within 38 or more genera. The two most prominent genera are Alpheus and Synalpheus, with species numbering well over 250 and 100, most snapping shrimp dig burrows and are common inhabitants of coral reefs, submerged seagrass flats, and oyster reefs. While most genera and species are found in tropical and temperate coastal and marine waters, Betaeus inhabits cold seas, when in colonies, the snapping shrimp can interfere with sonar and underwater communication. The shrimp are a source of noise in the ocean. The snapping shrimp grows to only 3–5 cm long and it is distinctive for its remarkably disproportionate large claw, larger than half the shrimps body. The claw can be on either arm of the body, rather, it has a pistol-like feature made of two parts. A joint allows the part to move backward into a right-angled position. When released, it snaps into the part of the claw, emitting an enormously powerful wave of bubbles capable of stunning larger fish. Some pistol shrimp species share burrows with goby fishes in a symbiotic relationship, the burrow is built and tended by the pistol shrimp, and the goby provides protection by watching out for danger. When both are out of the burrow, the shrimp maintains contact with the goby using its antennae, the goby, having the better vision, alerts the shrimp of danger using a characteristic tail movement, and then both retreat into the safety of the shared burrow. So far this association has been observed in species that inhabit coral reef habitats, eusocial behavior has been discovered in the genus Synalpheus. The species Synalpheus regalis lives inside sponges in colonies that can number over 300 members, all of them are the offspring of a single large female, the queen, and possibly a single male. The offspring are divided into workers who care for the young, pistol shrimp have also been noted for their ability to reverse claws. When the snapping claw is lost the missing limb will regenerate into a smaller claw, laboratory research has shown that severing the nerve of the snapping claw induces the conversion of the smaller limb into a second snapping claw. This phenomenon of symmetry in snapping shrimp has only been documented once in nature. The snapping shrimp competes with larger animals such as the sperm whale. The animal snaps a specialized claw shut to create a bubble that generates acoustic pressures of up to 80 kPa at a distance of 4 cm from the claw
28.
Dolphin
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Dolphins are a widely distributed and diverse group of aquatic mammals. They are a grouping within the order Cetacea, excluding whales and porpoises. The dolphins comprise the extant families Delphinidae, Platanistidae, Iniidae, and Pontoporiidae, there are 40 extant species of dolphins. Dolphins, alongside other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates and their closest living relatives are the hippopotamuses, having diverged about 40 million years ago. Dolphins range in size from the 1.7 m long and 50 kg Mauis dolphin to the 9.5 m and 10 t killer whale, several species exhibit sexual dimorphism, in that the males are larger than females. They have streamlined bodies and two limbs that are modified into flippers, though not quite as flexible as seals, some dolphins can travel at 55.5 km/h. Dolphins use their conical shaped teeth to capture fast moving prey and they have well-developed hearing which is adapted for both air and water and is so well developed that some can survive even if they are blind. Some species are adapted for diving to great depths. They have a layer of fat, or blubber, under the skin to keep warm in the cold water, although dolphins are widespread, most species prefer the warmer waters of the tropic zones, but some, like the right whale dolphin, prefer colder climates. Dolphins feed largely on fish and squid, but a few, like the killer whale, feed on large mammals, male dolphins typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them, mothers of some species fast and nurse their young for a relatively long period of time. Dolphins produce a variety of vocalizations, usually in the form of clicks, Dolphins are sometimes hunted in places like Japan, in an activity known as dolphin drive hunting. Besides drive hunting, they face threats from bycatch, habitat loss. Dolphins have been depicted in cultures worldwide. Dolphins occasionally feature in literature and film, as in the film series Free Willy, Dolphins are sometimes kept in captivity and trained to perform tricks, but breeding success has been poor and the animals often die within a few months of capture. The most common dolphins kept are killer whales and bottlenose dolphins, the name is originally from Greek δελφίς, dolphin, which was related to the Greek δελφύς, womb. The animals name can therefore be interpreted as meaning a fish with a womb, the name was transmitted via the Latin delphinus, which in Medieval Latin became dolfinus and in Old French daulphin, which reintroduced the ph into the word. The term mereswine has also historically been used, the term dolphin can be used to refer to, under the parvorder Odontoceti, all the species in the family Delphinidae and the river dolphin families Iniidae, Pontoporiidae, Lipotidae and Platanistidae
29.
Whale
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Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. They are a grouping within the infraorder Cetacea, usually excluding dolphins. Whales, dolphins and porpoises belong to the order Cetartiodactyla with even-toed ungulates and their closest living relatives are the hippopotamuses, the two parvorders of whales, baleen whales and toothed whales, are thought to have split apart around 34 million years ago. The whales comprise eight extant families, Balaenopteridae, Balaenidae, Cetotheriidae, Eschrichtiidae, Monodontidae, Physeteridae, Kogiidae, Whales are creatures of the open ocean, they feed, mate, give birth, suckle and raise their young at sea. So extreme is their adaptation to life underwater that they are unable to survive on land. Whales range in size from the 2.6 metres and 135 kilograms dwarf sperm whale to the 29.9 metres and 190 metric tons blue whale, the sperm whale is the largest toothed predator on earth. Several species exhibit sexual dimorphism, in that the females are larger than males, baleen whales have no teeth, instead they have plates of baleen, a fringe-like structure used to expel water while retaining the krill and plankton which they feed on. They use their throat pleats to expand the mouth to take in huge gulps of water, balaenids have heads that can make up 40% of their body mass to take in water. Toothed whales, on the hand, have conical teeth designed for catching fish or squid. Some species, such as whales, are well adapted for diving to great depths to catch squid. Whales have evolved from land-living mammals, as such they must breathe air regularly, though they can remain submerged for long periods. They have blowholes located on top of their heads, through air is taken in. They are warm-blooded, and have a layer of fat, or blubber, under the skin, with streamlined fusiform bodies and two limbs that are modified into flippers, whales can travel at up to 20 knots, though they are not as flexible or agile as seals. Whales produce a variety of vocalizations, notably the extended songs of the humpback whale. Although whales are widespread, most species prefer the waters of the Northern and Southern Hemispheres. Species such as humpbacks and blue whales are capable of travelling thousands of miles without feeding, males typically mate with multiple females every year, but females only mate every two to three years. Calves are typically born in the spring and summer months and females bear all the responsibility for raising them, mothers of some species fast and nurse their young for one to two years. Once relentlessly hunted for their products, whales are now protected by international law, the North Atlantic right whales nearly became extinct in the twentieth century, with a population low of 450, and the North Pacific gray whale population is ranked Critically Endangered by the IUCN
30.
Aeration
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Aeration is the process by which air is circulated through, mixed with or dissolved in a liquid or substance. Aeration of liquids is achieved by, passing the liquid air by means of fountains, cascades. Ceramics are suitable for this purpose, often involving dispersion of air or gas bubbles through the porous ceramic into a liquid. The smaller the bubbles, the gas is exposed to the liquid increasing the gas transfer efficiency. Diffusers or spargers can also be designed into the system to cause turbulence or mixing if desired, porous ceramic diffusers are made by fusing aluminum oxide grains using porcelain bonds to form a strong, uniformly porous and homogeneous structure. The naturally hydrophilic material is easily wetted resulting in the production of fine, on a given volume of air or liquid, the surface area changes proportionally with drop or bubble size, the very surface area where exchange can occur. Utilizing extremely small bubbles or drops increases the rate of gas due to the higher contact surface area. The pores which these bubbles pass through are generally micrometre-size, to smooth the flow of tap water at the faucet. Production of aerated water or cola for drinking purposes, secondary treatment of sewage or industrial wastewater through use of aerating mixers/diffusers. To increase the content of water used to house animals, such as aquarium fish or fish farm To increase oxygen content of wort or must to allow yeast to propagate. To dispel other dissolved gases such as carbon dioxide or chlorine, in chemistry, to oxidise a compound dissolved or suspended in water. To induce mixing of a body of still water. In soil, aeration refers to the extent of air gaps, soil aeration is the process of using mechanized or manual equipment to either puncture the soil with spikes or remove approximately 1 x 2 cores of soil from the ground. Aeration may be overlooked when trying to restore a lawn but is vital to bring it back to health and it improves drainage and reduces puddles formation. Spike aeration involves the use of a machine with spikes up to a foot or more in length. It is sometimes used to address issues in areas with turf. There are many types of lawn aerators including walk behind models, ride on versions and tractor pulled versions, refers to the process in which air is absorbed into the food item. It refers to the lightness of cakes and bread, as measured by the type of pores they contain, and the color and texture of some sauces which have incorporated air bubbles
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Chemical engineering
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A chemical engineer designs large-scale processes that convert chemicals, raw materials, living cells, microorganisms and energy into useful forms and products. A1996 British Journal for the History of Science article cites James F. Donnelly for mentioning an 1839 reference to chemical engineering in relation to the production of sulfuric acid. In the same however, George E. Davis, an English consultant, was credited for having coined the term. The History of Science in United States, An Encyclopedia puts this at around 1890, Chemical engineering, describing the use of mechanical equipment in the chemical industry, became common vocabulary in England after 1850. By 1910, the profession, chemical engineer, was already in use in Britain. Chemical engineering emerged upon the development of operations, a fundamental concept of the discipline of chemical engineering. Most authors agree that Davis invented the concept of operations if not substantially developed it. He gave a series of lectures on unit operations at the Manchester Technical School in 1887, three years before Davis lectures, Henry Edward Armstrong taught a degree course in chemical engineering at the City and Guilds of London Institute. Armstrongs course failed simply because its graduates, were not especially attractive to employers. Employers of the time would have rather hired chemists and mechanical engineers, starting from 1888, Lewis M. Norton taught at MIT the first chemical engineering course in the United States. Nortons course was contemporaneous and essentially similar with Armstrongs course, both courses, however, simply merged chemistry and engineering subjects. Its practitioners had difficulty convincing engineers that they were engineers and chemists that they were not simply chemists, unit operations was introduced into the course by William Hultz Walker in 1905. By the early 1920s, unit operations became an important aspect of engineering at MIT and other US universities. For instance, it defined chemical engineering to be a science of itself, unit operations in a 1922 report, and with which principle, it had published a list of academic institutions which offered satisfactory chemical engineering courses. Meanwhile, promoting chemical engineering as a science in Britain lead to the establishment of the Institution of Chemical Engineers in 1922. IChemE likewise helped make unit operations considered essential to the discipline, by the 1940s, it became clear that unit operations alone was insufficient in developing chemical reactors. While the predominance of unit operations in chemical engineering courses in Britain, along with other novel concepts, such process systems engineering, a second paradigm was defined. Transport phenomena gave an analytical approach to chemical engineering while PSE focused on its elements, such as control system
32.
Metallurgy
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The production of metals involves the processing of ores to extract the metal they contain, and the mixture of metals, sometimes with other elements, to produce alloys. Metallurgy is distinguished from the craft of metalworking, although metalworking relies on metallurgy, as medicine relies on medical science, Metallurgy is subdivided into ferrous metallurgy and non-ferrous metallurgy or colored metallurgy. Ferrous metallurgy involves processes and alloys based on iron while non-ferrous metallurgy involves processes, the production of ferrous metals accounts for 95 percent of world metal production. The roots of metallurgy derive from Ancient Greek, μεταλλουργός, metallourgós, worker in metal, from μέταλλον, métallon, metal + ἔργον, érgon, in the late 19th century it was extended to the more general scientific study of metals, alloys, and related processes. In English, the pronunciation is the more common one in the UK. The /ˈmetələrdʒi/ pronunciation is the common one in the USA. The earliest recorded metal employed by humans appears to be gold, small amounts of natural gold have been found in Spanish caves used during the late Paleolithic period, c.40,000 BC. Silver, copper, tin and meteoric iron can also be found in native form, egyptian weapons made from meteoric iron in about 3000 BC were highly prized as daggers from heaven. Certain metals, notably tin, lead and copper, can be recovered from their ores by simply heating the rocks in a fire or blast furnace, a process known as smelting. The first evidence of this extractive metallurgy dates from the 5th and 6th millennia BC and was found in the sites of Majdanpek, Yarmovac and Plocnik. To date, the earliest evidence of copper smelting is found at the Belovode site, other signs of early metals are found from the third millennium BC in places like Palmela, Los Millares, and Stonehenge. However, the ultimate beginnings cannot be ascertained and new discoveries are both continuous and ongoing. These first metals were single ones or as found, about 3500 BC, it was discovered that by combining copper and tin, a superior metal could be made, an alloy called bronze, representing a major technological shift known as the Bronze Age. The extraction of iron from its ore into a metal is much more difficult than for copper or tin. The process appears to have been invented by the Hittites in about 1200 BC, the secret of extracting and working iron was a key factor in the success of the Philistines. Historical developments in ferrous metallurgy can be found in a variety of past cultures. A 16th century book by Georg Agricola called De re metallica describes the highly developed and complex processes of mining metal ores, metal extraction, Agricola has been described as the father of metallurgy. Extractive metallurgy is the practice of removing valuable metals from an ore, in order to convert a metal oxide or sulphide to a purer metal, the ore must be reduced physically, chemically, or electrolytically
33.
Engineer
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Engineers design materials, structures, and systems while considering the limitations imposed by practicality, regulation, safety, and cost. The word engineer is derived from the Latin words ingeniare and ingenium, the work of engineers forms the link between scientific discoveries and their subsequent applications to human and business needs and quality of life. His/her work is predominantly intellectual and varied and not of a mental or physical character. It requires the exercise of original thought and judgement and the ability to supervise the technical, he/she is thus placed in a position to make contributions to the development of engineering science or its applications. In due time he/she will be able to give authoritative technical advice, much of an engineers time is spent on researching, locating, applying, and transferring information. Indeed, research suggests engineers spend 56% of their time engaged in various information behaviours, Engineers must weigh different design choices on their merits and choose the solution that best matches the requirements. Their crucial and unique task is to identify, understand, Engineers apply techniques of engineering analysis in testing, production, or maintenance. Analytical engineers may supervise production in factories and elsewhere, determine the causes of a process failure and they also estimate the time and cost required to complete projects. Supervisory engineers are responsible for major components or entire projects, Engineering analysis involves the application of scientific analytic principles and processes to reveal the properties and state of the system, device or mechanism under study. Most engineers specialize in one or more engineering disciplines, numerous specialties are recognized by professional societies, and each of the major branches of engineering has numerous subdivisions. Civil engineering, for example, includes structural and transportation engineering and materials engineering include ceramic, metallurgical, mechanical engineering cuts across just about every discipline since its core essence is applied physics. Engineers also may specialize in one industry, such as vehicles, or in one type of technology. Several recent studies have investigated how engineers spend their time, that is, research suggests that there are several key themes present in engineers’ work, technical work, social work, computer-based work, information behaviours. Amongst other more detailed findings, a recent work sampling study found that engineers spend 62. 92% of their time engaged in work,40. 37% in social work. The time engineers spend engaged in activities is also reflected in the competencies required in engineering roles. There are many branches of engineering, each of which specializes in specific technologies, typically engineers will have deep knowledge in one area and basic knowledge in related areas. When developing a product, engineers work in interdisciplinary teams. For example, when building robots an engineering team will typically have at least three types of engineers, a mechanical engineer would design the body and actuators
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Fluid dynamics
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In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids. It has several subdisciplines, including aerodynamics and hydrodynamics, before the twentieth century, hydrodynamics was synonymous with fluid dynamics. This is still reflected in names of some fluid dynamics topics, like magnetohydrodynamics and hydrodynamic stability, the foundational axioms of fluid dynamics are the conservation laws, specifically, conservation of mass, conservation of linear momentum, and conservation of energy. These are based on mechanics and are modified in quantum mechanics. They are expressed using the Reynolds transport theorem, in addition to the above, fluids are assumed to obey the continuum assumption. Fluids are composed of molecules that collide with one another and solid objects, however, the continuum assumption assumes that fluids are continuous, rather than discrete. The fact that the fluid is made up of molecules is ignored. The unsimplified equations do not have a general solution, so they are primarily of use in Computational Fluid Dynamics. The equations can be simplified in a number of ways, all of which make them easier to solve, some of the simplifications allow some simple fluid dynamics problems to be solved in closed form. Three conservation laws are used to solve fluid dynamics problems, the conservation laws may be applied to a region of the flow called a control volume. A control volume is a volume in space through which fluid is assumed to flow. The integral formulations of the laws are used to describe the change of mass, momentum. Mass continuity, The rate of change of fluid mass inside a control volume must be equal to the net rate of flow into the volume. Mass flow into the system is accounted as positive, and since the vector to the surface is opposite the sense of flow into the system the term is negated. The first term on the right is the net rate at which momentum is convected into the volume, the second term on the right is the force due to pressure on the volumes surfaces. The first two terms on the right are negated since momentum entering the system is accounted as positive, the third term on the right is the net acceleration of the mass within the volume due to any body forces. Surface forces, such as forces, are represented by F surf. The following is the form of the momentum conservation equation
35.
Star-nosed mole
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The star-nosed mole is a small mole found in wet low areas of eastern Canada and the northeastern United States, with records extending along the Atlantic coast as far as extreme southeastern Georgia. It is the member of the tribe Condylurini and the genus Condylura. With the help of its Eimers organs, it may be perfectly poised to detect seismic wave vibrations, adults are 15 to 20 cm in length, weigh about 55 grams, and have 44 teeth. The moles most distinctive feature is a circle of 22 mobile, pink, fleshy tentacles at the end of its snout and these are used to identify food by touch, such as worms, insects and crustaceans. The extremely sensitive star-like structure is covered with minute touch receptors known as Eimers organs, the nose is about 1 cm in diameter with roughly 25,000 Eimers organs distributed on 22 appendages. Eimers organs were first described in the European mole in 1871 by German zoologist Theodor Eimer, other mole species also possess Eimers organs, though they are not as specialized or numerous as in the star-nosed mole. The nasal star and dentition of this appear to be primarily adapted to exploit extremely small prey. A report in the journal Nature gives this animal the title of fastest-eating mammal, taking as short as 120 milliseconds to identify and its brain decides in approximately 8 ms if a prey is edible or not. This speed is at the limit of the speed of neurons and these moles are also able to smell underwater, accomplished by exhaling air bubbles onto objects or scent trails and then inhaling the bubbles to carry scents back through the nose. The star-nosed mole lives in wet areas and eats small invertebrates, aquatic insects, worms, mollusks, small amphibians. Condylura cristata has also found in dry meadows farther away from water. They have also found in the Great Smokey Mountains as high up as 1676 meters. However, the star-nose mole does prefer wet, poorly drained areas and it is a good swimmer and can forage along the bottoms of streams and ponds. Like other moles, this animal digs shallow surface tunnels for foraging, often and it is active day and night and remains active in winter, when it has been observed tunneling through the snow and swimming in ice-covered streams. Little is known about the behavior of the species. The star-nosed mole mates in winter or early spring. However, females are known to have a litter if their first is unsuccessful. At birth, each offspring is about 5 cm long, hairless and their eyes, ears, and star are all sealed, only opening and becoming useful about 14 days after birth
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American water shrew
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The American water shrew or northern water shrew, is found in the nearctic faunal region located throughout the mountain ranges of northern United States and in Canada and Alaska. The American Water Shrew is considered a species that is sexual dimorphic in which the males are in bigger and heavier than the females. The size of the shrew can be anywhere from 130–170 mm and their tails range from 57–89 mm. The shrew contains black and brown fur colors and changes depending on the season, the color will change to lighter brown in the summer and a black color in the winter. Air bubbles are trapped in the thick fur when the animal dives underwater, the air bubbles help the shrew with buoyancy and also allow it to engage in a behavior called “water-walking”. The water shrew can dive underwater for about 15 seconds, but is able to if it is swimming vigorously. The air bubbles allow the shrew to swim, but as soon as the shrew stops swimming and its feet have a fringe of hairs, more visible on the larger hind feet, which allow this animal to run on the waters surface. The American Water Shrew has a larger skull ranging from 21 to 23 mm and width 10 to 11 mm and they swim well and make short dives in search of food. The shrew prefers aquatic insects such as, stone flies and crane flies and they are known to also feed on small fish, vegetation, and snails. Shrews require a lot of food and cannot go without food for anymore than three hours because of their metabolic rate. It is thought that they use echolocation to find prey. The American Water Shrew tends to breed from December to September and females usually have a gestation period where offspring will be born in the spring. They usually produce two to three litters during that time and these litters can contain anywhere from three to ten offspring. The American water shrew has nine subspecies, List of solitary animals
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Oscillation
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Oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. The term vibration is used to describe mechanical oscillation. Familiar examples of oscillation include a swinging pendulum and alternating current power, the simplest mechanical oscillating system is a weight attached to a linear spring subject to only weight and tension. Such a system may be approximated on an air table or ice surface, the system is in an equilibrium state when the spring is static. If the system is displaced from the equilibrium, there is a net restoring force on the mass, tending to bring it back to equilibrium. However, in moving the back to the equilibrium position, it has acquired momentum which keeps it moving beyond that position. If a constant force such as gravity is added to the system, the time taken for an oscillation to occur is often referred to as the oscillatory period. All real-world oscillator systems are thermodynamically irreversible and this means there are dissipative processes such as friction or electrical resistance which continually convert some of the energy stored in the oscillator into heat in the environment. Thus, oscillations tend to decay with time there is some net source of energy into the system. The simplest description of this process can be illustrated by oscillation decay of the harmonic oscillator. In addition, a system may be subject to some external force. In this case the oscillation is said to be driven, some systems can be excited by energy transfer from the environment. This transfer typically occurs where systems are embedded in some fluid flow, at sufficiently large displacements, the stiffness of the wing dominates to provide the restoring force that enables an oscillation. The harmonic oscillator and the systems it models have a degree of freedom. More complicated systems have more degrees of freedom, for two masses and three springs. In such cases, the behavior of each variable influences that of the others and this leads to a coupling of the oscillations of the individual degrees of freedom. For example, two pendulum clocks mounted on a wall will tend to synchronise. This phenomenon was first observed by Christiaan Huygens in 1665, more special cases are the coupled oscillators where energy alternates between two forms of oscillation
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Surface tension
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Surface tension is the elastic tendency of a fluid surface which makes it acquire the least surface area possible. Surface tension allows insects, usually denser than water, to float, at liquid-air interfaces, surface tension results from the greater attraction of liquid molecules to each other than to the molecules in the air. The net effect is a force at its surface that causes the liquid to behave as if its surface were covered with a stretched elastic membrane. Thus, the surface becomes under tension from the imbalanced forces, because of the relatively high attraction of water molecules for each other through a web of hydrogen bonds, water has a higher surface tension compared to that of most other liquids. Surface tension is an important factor in the phenomenon of capillarity, Surface tension has the dimension of force per unit length, or of energy per unit area. The two are equivalent, but when referring to energy per unit of area, it is common to use the surface energy. In materials science, surface tension is used for either surface stress or surface free energy, the cohesive forces among liquid molecules are responsible for the phenomenon of surface tension. In the bulk of the liquid, each molecule is pulled equally in every direction by neighboring liquid molecules, the molecules at the surface do not have the same molecules on all sides of them and therefore are pulled inwards. This creates some internal pressure and forces liquid surfaces to contract to the minimal area, Surface tension is responsible for the shape of liquid droplets. Although easily deformed, droplets of water tend to be pulled into a shape by the imbalance in cohesive forces of the surface layer. In the absence of forces, including gravity, drops of virtually all liquids would be approximately spherical. The spherical shape minimizes the necessary wall tension of the surface according to Laplaces law. Another way to view surface tension is in terms of energy, a molecule in contact with a neighbor is in a lower state of energy than if it were alone. The interior molecules have as many neighbors as they can possibly have, for the liquid to minimize its energy state, the number of higher energy boundary molecules must be minimized. The minimized quantity of boundary molecules results in a surface area. As a result of surface area minimization, a surface will assume the smoothest shape it can, since any curvature in the surface shape results in greater area, a higher energy will also result. Consequently, the surface will push back against any curvature in much the way as a ball pushed uphill will push back to minimize its gravitational potential energy. Bubbles in pure water are unstable, the addition of surfactants, however, can have a stabilizing effect on the bubbles
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Thermal conductivity
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In physics, thermal conductivity is the property of a material to conduct heat. It is evaluated primarily in terms of Fouriers Law for heat conduction, heat transfer occurs at a lower rate across materials of low thermal conductivity than across materials of high thermal conductivity. Correspondingly, materials of high thermal conductivity are used in heat sink applications. The thermal conductivity of a material may depend on temperature, the reciprocal of thermal conductivity is called thermal resistivity. Thermal conductivity is actually a tensor, which means it is possible to have different values in different directions, in SI units, thermal conductivity is measured in watts per meter-kelvin. The dimension of thermal conductivity is M1L1T−3Θ−1 and these variables are mass, length, time, and temperature. In Imperial units, thermal conductivity is measured in BTU/, other units which are closely related to the thermal conductivity are in common use in the construction and textile industries. The construction industry makes use of such as the R-value. Although related to the conductivity of a material used in an insulation product, R-. Likewise the textile industry has several units including the tog and the clo which express thermal resistance of a material in a way analogous to the R-values used in the construction industry, there are a number of ways to measure thermal conductivity. Each of these is suitable for a range of materials, depending on the thermal properties. There is a distinction between steady-state and transient techniques, in general, steady-state techniques are useful when the temperature of the material does not change with time. This makes the signal analysis straightforward, the disadvantage is that a well-engineered experimental setup is usually needed. The Divided Bar is the most common used for consolidated rock solids. Thermal conductivity is important in science, research, electronics, building insulation and related fields. Several materials are shown in the list of thermal conductivities and these should be considered approximate due to the uncertainties related to material definitions. High energy generation rates within electronics or turbines require the use of materials with high thermal conductivity such as copper, aluminium, the reciprocal of thermal conductivity is thermal resistivity, usually expressed in kelvin-meters per watt. For a given thickness of a material, that particular constructions thermal resistance, unfortunately, there are differing definitions for these terms
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Adiabatic process
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In thermodynamics, an adiabatic process is one that occurs without transfer of heat or matter between a thermodynamic system and its surroundings. In an adiabatic process, energy is transferred only as work, the adiabatic process provides a rigorous conceptual basis for the theory used to expound the first law of thermodynamics, and as such it is a key concept in thermodynamics. The adiabatic flame temperature is the temperature that would be achieved by a if the process of combustion took place in the absence of heat loss to the surroundings. A process that does not involve the transfer of heat or matter into or out of a system, so that Q =0, is called an adiabatic process, the assumption that a process is adiabatic is a frequently made simplifying assumption. Even though the cylinders are not insulated and are quite conductive, the same can be said to be true for the expansion process of such a system. The assumption of adiabatic isolation of a system is a useful one, the behaviour of actual machines deviates from these idealizations, but the assumption of such perfect behaviour provide a useful first approximation of how the real world works. According to Laplace, when sound travels in a gas, there is no loss of heat in the medium and the propagation of sound is adiabatic. For this adiabatic process, the modulus of elasticity E = γP where γ is the ratio of specific heats at constant pressure and at constant volume, such a process is called an isentropic process and is said to be reversible. Fictively, if the process is reversed, the energy added as work can be recovered entirely as work done by the system, if the walls of a system are not adiabatic, and energy is transferred in as heat, entropy is transferred into the system with the heat. Such a process is neither adiabatic nor isentropic, having Q >0, naturally occurring adiabatic processes are irreversible. The transfer of energy as work into an isolated system can be imagined as being of two idealized extreme kinds. In one such kind, there is no entropy produced within the system, in nature, this ideal kind occurs only approximately, because it demands an infinitely slow process and no sources of dissipation. The other extreme kind of work is work, for which energy is added as work solely through friction or viscous dissipation within the system. The second law of thermodynamics observes that a process, of transfer of energy as work, always consists at least of isochoric work. Every natural process, adiabatic or not, is irreversible, with ΔS >0, the adiabatic compression of a gas causes a rise in temperature of the gas. Adiabatic expansion against pressure, or a spring, causes a drop in temperature, in contrast, free expansion is an isothermal process for an ideal gas. Adiabatic heating occurs when the pressure of a gas is increased from work done on it by its surroundings and this finds practical application in diesel engines which rely on the lack of quick heat dissipation during their compression stroke to elevate the fuel vapor temperature sufficiently to ignite it. Adiabatic heating occurs in the Earths atmosphere when an air mass descends, for example, in a wind, Foehn wind
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Pressure
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Pressure is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure is the relative to the ambient pressure. Various units are used to express pressure, Pressure may also be expressed in terms of standard atmospheric pressure, the atmosphere is equal to this pressure and the torr is defined as 1⁄760 of this. Manometric units such as the centimetre of water, millimetre of mercury, Pressure is the amount of force acting per unit area. The symbol for it is p or P, the IUPAC recommendation for pressure is a lower-case p. However, upper-case P is widely used. The usage of P vs p depends upon the field in one is working, on the nearby presence of other symbols for quantities such as power and momentum. Mathematically, p = F A where, p is the pressure, F is the normal force and it relates the vector surface element with the normal force acting on it. It is incorrect to say the pressure is directed in such or such direction, the pressure, as a scalar, has no direction. The force given by the relationship to the quantity has a direction. If we change the orientation of the element, the direction of the normal force changes accordingly. Pressure is distributed to solid boundaries or across arbitrary sections of normal to these boundaries or sections at every point. It is a parameter in thermodynamics, and it is conjugate to volume. The SI unit for pressure is the pascal, equal to one newton per square metre and this name for the unit was added in 1971, before that, pressure in SI was expressed simply in newtons per square metre. Other units of pressure, such as pounds per square inch, the CGS unit of pressure is the barye, equal to 1 dyn·cm−2 or 0.1 Pa. Pressure is sometimes expressed in grams-force or kilograms-force per square centimetre, but using the names kilogram, gram, kilogram-force, or gram-force as units of force is expressly forbidden in SI. The technical atmosphere is 1 kgf/cm2, since a system under pressure has potential to perform work on its surroundings, pressure is a measure of potential energy stored per unit volume. It is therefore related to density and may be expressed in units such as joules per cubic metre. Similar pressures are given in kilopascals in most other fields, where the prefix is rarely used
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Mass
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In physics, mass is a property of a physical body. It is the measure of a resistance to acceleration when a net force is applied. It also determines the strength of its gravitational attraction to other bodies. The basic SI unit of mass is the kilogram, Mass is not the same as weight, even though mass is often determined by measuring the objects weight using a spring scale, rather than comparing it directly with known masses. An object on the Moon would weigh less than it does on Earth because of the lower gravity and this is because weight is a force, while mass is the property that determines the strength of this force. In Newtonian physics, mass can be generalized as the amount of matter in an object, however, at very high speeds, special relativity postulates that energy is an additional source of mass. Thus, any body having mass has an equivalent amount of energy. In addition, matter is a defined term in science. There are several distinct phenomena which can be used to measure mass, active gravitational mass measures the gravitational force exerted by an object. Passive gravitational mass measures the force exerted on an object in a known gravitational field. The mass of an object determines its acceleration in the presence of an applied force, according to Newtons second law of motion, if a body of fixed mass m is subjected to a single force F, its acceleration a is given by F/m. A bodys mass also determines the degree to which it generates or is affected by a gravitational field and this is sometimes referred to as gravitational mass. The standard International System of Units unit of mass is the kilogram, the kilogram is 1000 grams, first defined in 1795 as one cubic decimeter of water at the melting point of ice. Then in 1889, the kilogram was redefined as the mass of the prototype kilogram. As of January 2013, there are proposals for redefining the kilogram yet again. In this context, the mass has units of eV/c2, the electronvolt and its multiples, such as the MeV, are commonly used in particle physics. The atomic mass unit is 1/12 of the mass of a carbon-12 atom, the atomic mass unit is convenient for expressing the masses of atoms and molecules. Outside the SI system, other units of mass include, the slug is an Imperial unit of mass, the pound is a unit of both mass and force, used mainly in the United States
