1.
Ice cream
–
Ice cream is a sweetened frozen food typically eaten as a snack or dessert. It is usually made from dairy products, such as milk and cream and it is typically sweetened with sugar or sugar substitutes. Typically, flavourings and colourings are added in addition to stabilizers, the mixture is stirred to incorporate air spaces and cooled below the freezing point of water to prevent detectable ice crystals from forming. The result is a smooth, semi-solid foam that is solid at low temperatures. It becomes more malleable as its temperature increases, the meaning of the phrase ice cream varies from one country to another. Phrases such as frozen custard, frozen yogurt, sorbet, gelato, products that do not meet the criteria to be called ice cream are labelled frozen dairy dessert instead. In other countries, such as Italy and Argentina, one word is used for all variants, analogues made from dairy alternatives, such as goats or sheeps milk, or milk substitutes, are available for those who are lactose intolerant, allergic to dairy protein, or vegan. Ice cream may be served in dishes, for eating with a spoon, or in cones, Ice cream may be served with other desserts, such as apple pie. Ice cream is used to other desserts, including ice cream floats, sundaes, milkshakes, ice cream cakes and even baked items. During the 5th century BC, ancient Greeks ate snow mixed with honey, the father of modern medicine, Hippocrates, encouraged his Ancient Greek patients to eat ice as it livens the life-juices and increases the well-being. In 400 BC, the Persians invented a special chilled food, made of water and vermicelli. The ice was mixed with saffron, fruits, and various other flavours, a frozen mixture of milk and rice was used in China around 200 BC. The Roman Emperor Nero had ice brought from the mountains and combined it with fruit toppings to create chilled delicacies, in the sixteenth century, the Mughal emperors used relays of horsemen to bring ice from the Hindu Kush to Delhi, where it was used in fruit sorbets. When Italian duchess Catherine de Medici married the Duke of Orléans in 1533, there is no historical evidence to support these legends, which first appeared during the 19th century. The first recipe in French for flavoured ices appears in 1674, recipes for sorbetti saw publication in the 1694 edition of Antonio Latinis Lo Scalco alla Moderna. Recipes for flavoured ices begin to appear in François Massialots Nouvelle Instruction pour les Confitures, les Liqueurs, et les Fruits, Massialots recipes result in a coarse, pebbly texture. Latini claims that the results of his recipes should have the consistency of sugar. Ice cream recipes first appeared in England in the 18th century, the recipe for ice cream was published in Mrs. Mary Ealess Receipts in London in 1718
Ice cream
–
A
cocktail glass of ice cream, with
whipped cream and a wafer
Ice cream
–
A
yakhchal, an ancient type of ice house, in
Yazd,
Iran
Ice cream
–
Italian duchess
Catherine de' Medici, credited with introducing ice cream into Europe in the 16th century
Ice cream
–
Title page to The Art of Cookery by
Hannah Glasse
2.
Nitrogen
–
Nitrogen is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772, although Carl Wilhelm Scheele and Henry Cavendish had independently done so at about the same time, Rutherford is generally accorded the credit because his work was published first. Nitrogen is the lightest member of group 15 of the periodic table, the name comes from the Greek πνίγειν to choke, directly referencing nitrogens asphyxiating properties. It is an element in the universe, estimated at about seventh in total abundance in the Milky Way. At standard temperature and pressure, two atoms of the element bind to form dinitrogen, a colourless and odorless diatomic gas with the formula N2, dinitrogen forms about 78% of Earths atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids, in the nucleic acids, the human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes movement of the element from the air, into the biosphere and organic compounds, many industrially important compounds, such as ammonia, nitric acid, organic nitrates, and cyanides, contain nitrogen. The extremely strong bond in elemental nitrogen, the second strongest bond in any diatomic molecule. Synthetically produced ammonia and nitrates are key industrial fertilisers, and fertiliser nitrates are key pollutants in the eutrophication of water systems. Apart from its use in fertilisers and energy-stores, nitrogen is a constituent of organic compounds as diverse as Kevlar used in high-strength fabric, Nitrogen is a constituent of every major pharmacological drug class, including antibiotics. Many notable nitrogen-containing drugs, such as the caffeine and morphine or the synthetic amphetamines. Nitrogen compounds have a long history, ammonium chloride having been known to Herodotus. They were well known by the Middle Ages, alchemists knew nitric acid as aqua fortis, as well as other nitrogen compounds such as ammonium salts and nitrate salts. The mixture of nitric and hydrochloric acids was known as aqua regia, celebrated for its ability to dissolve gold, the discovery of nitrogen is attributed to the Scottish physician Daniel Rutherford in 1772, who called it noxious air. Though he did not recognise it as a different chemical substance, he clearly distinguished it from Joseph Blacks fixed air. The fact that there was a component of air that does not support combustion was clear to Rutherford, Nitrogen was also studied at about the same time by Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley, who referred to it as burnt air or phlogisticated air. Nitrogen gas was inert enough that Antoine Lavoisier referred to it as air or azote, from the Greek word άζωτικός. In an atmosphere of nitrogen, animals died and flames were extinguished
Nitrogen
–
Liquid nitrogen
Nitrogen
–
Spectral lines of nitrogen
Nitrogen
–
Nitrogen discharge (spectrum) tube
Nitrogen
–
Table tennis ball made from nitrocellulose.
3.
Boiling point
–
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor. The boiling point of a liquid varies depending upon the environmental pressure. A liquid in a vacuum has a lower boiling point than when that liquid is at atmospheric pressure. A liquid at high pressure has a boiling point than when that liquid is at atmospheric pressure. For a given pressure, different liquids boil at different temperatures, for example, water boils at 100 °C at sea level, but at 93.4 °C at 2,000 metres altitude. The normal boiling point of a liquid is the case in which the vapor pressure of the liquid equals the defined atmospheric pressure at sea level,1 atmosphere. At that temperature, the pressure of the liquid becomes sufficient to overcome atmospheric pressure. The standard boiling point has been defined by IUPAC since 1982 as the temperature at which boiling occurs under a pressure of 1 bar, the heat of vaporization is the energy required to transform a given quantity of a substance from a liquid into a gas at a given pressure. Liquids may change to a vapor at temperatures below their boiling points through the process of evaporation, evaporation is a surface phenomenon in which molecules located near the liquids edge, not contained by enough liquid pressure on that side, escape into the surroundings as vapor. On the other hand, boiling is a process in which molecules anywhere in the liquid escape, a saturated liquid contains as much thermal energy as it can without boiling. The saturation temperature is the temperature for a corresponding saturation pressure at which a liquid boils into its vapor phase, the liquid can be said to be saturated with thermal energy. Any addition of energy results in a phase transition. If the pressure in a system remains constant, a vapor at saturation temperature will begin to condense into its liquid phase as thermal energy is removed, similarly, a liquid at saturation temperature and pressure will boil into its vapor phase as additional thermal energy is applied. The boiling point corresponds to the temperature at which the pressure of the liquid equals the surrounding environmental pressure. Thus, the point is dependent on the pressure. Boiling points may be published with respect to the NIST, USA standard pressure of 101.325 kPa, at higher elevations, where the atmospheric pressure is much lower, the boiling point is also lower. The boiling point increases with increased pressure up to the critical point, the boiling point cannot be increased beyond the critical point. Likewise, the point decreases with decreasing pressure until the triple point is reached
Boiling point
–
Boiling water
4.
Celsius
–
Celsius, also known as centigrade, is a metric scale and unit of measurement for temperature. As an SI derived unit, it is used by most countries in the world and it is named after the Swedish astronomer Anders Celsius, who developed a similar temperature scale. The degree Celsius can refer to a temperature on the Celsius scale as well as a unit to indicate a temperature interval. Before being renamed to honour Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps. The scale is based on 0° for the point of water. This scale is widely taught in schools today, by international agreement the unit degree Celsius and the Celsius scale are currently defined by two different temperatures, absolute zero, and the triple point of VSMOW. This definition also precisely relates the Celsius scale to the Kelvin scale, absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C. The temperature of the point of water is defined as precisely 273.16 K at 611.657 pascals pressure. This definition fixes the magnitude of both the degree Celsius and the kelvin as precisely 1 part in 273.16 of the difference between absolute zero and the point of water. Thus, it sets the magnitude of one degree Celsius and that of one kelvin as exactly the same, additionally, it establishes the difference between the two scales null points as being precisely 273.15 degrees. In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the point of ice is essentially unaffected by pressure. He also determined with precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the point of his temperature scale, being the boiling point. This pressure is known as one standard atmosphere, the BIPMs 10th General Conference on Weights and Measures later defined one standard atmosphere to equal precisely 1013250dynes per square centimetre. On 19 May 1743 he published the design of a mercury thermometer, in 1744, coincident with the death of Anders Celsius, the Swedish botanist Carolus Linnaeus reversed Celsiuss scale. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden, since the 19th century, the scientific and thermometry communities worldwide referred to this scale as the centigrade scale. Temperatures on the scale were often reported simply as degrees or. More properly, what was defined as centigrade then would now be hectograde.2 gradians, for scientific use, Celsius is the term usually used, with centigrade otherwise continuing to be in common but decreasing use, especially in informal contexts in English-speaking countries
Celsius
–
A
thermometer calibrated in degrees Celsius
5.
Kelvin
–
The kelvin is a unit of measure for temperature based upon an absolute scale. It is one of the seven units in the International System of Units and is assigned the unit symbol K. The kelvin is defined as the fraction 1⁄273.16 of the temperature of the triple point of water. In other words, it is defined such that the point of water is exactly 273.16 K. The Kelvin scale is named after the Belfast-born, Glasgow University engineer and physicist William Lord Kelvin, unlike the degree Fahrenheit and degree Celsius, the kelvin is not referred to or typeset as a degree. The kelvin is the unit of temperature measurement in the physical sciences, but is often used in conjunction with the Celsius degree. The definition implies that absolute zero is equivalent to −273.15 °C, Kelvin calculated that absolute zero was equivalent to −273 °C on the air thermometers of the time. This absolute scale is known today as the Kelvin thermodynamic temperature scale, when spelled out or spoken, the unit is pluralised using the same grammatical rules as for other SI units such as the volt or ohm. When reference is made to the Kelvin scale, the word kelvin—which is normally a noun—functions adjectivally to modify the noun scale and is capitalized, as with most other SI unit symbols there is a space between the numeric value and the kelvin symbol. Before the 13th CGPM in 1967–1968, the unit kelvin was called a degree and it was distinguished from the other scales with either the adjective suffix Kelvin or with absolute and its symbol was °K. The latter term, which was the official name from 1948 until 1954, was ambiguous since it could also be interpreted as referring to the Rankine scale. Before the 13th CGPM, the form was degrees absolute. The 13th CGPM changed the name to simply kelvin. Its measured value was 0.01028 °C with an uncertainty of 60 µK, the use of SI prefixed forms of the degree Celsius to express a temperature interval has not been widely adopted. In 2005 the CIPM embarked on a program to redefine the kelvin using a more experimentally rigorous methodology, the current definition as of 2016 is unsatisfactory for temperatures below 20 K and above 1300 K. In particular, the committee proposed redefining the kelvin such that Boltzmanns constant takes the exact value 1. 3806505×10−23 J/K, from a scientific point of view, this will link temperature to the rest of SI and result in a stable definition that is independent of any particular substance. From a practical point of view, the redefinition will pass unnoticed, the kelvin is often used in the measure of the colour temperature of light sources. Colour temperature is based upon the principle that a black body radiator emits light whose colour depends on the temperature of the radiator, black bodies with temperatures below about 4000 K appear reddish, whereas those above about 7500 K appear bluish
Kelvin
–
Lord Kelvin, the namesake of the unit
Kelvin
–
A thermometer calibrated in degrees Celsius (left) and kelvins (right).
6.
Fahrenheit
–
Fahrenheit is a temperature scale based on one proposed in 1724 by the physicist Daniel Gabriel Fahrenheit, after whom the scale is named. It uses the degree Fahrenheit as the unit, several accounts of how he originally defined his scale exist. The lower defining point,0 °F, was established as the temperature of a solution of brine made from parts of ice. Further limits were established as the point of ice and his best estimate of the average human body temperature. All other countries in the world now use the Celsius scale, defined since 1954 by absolute zero being −273.15 °C, on the Fahrenheit scale, the freezing point of water is 32 degrees Fahrenheit and the boiling point is 212 °F. This puts the boiling and freezing points of water exactly 180 degrees apart, therefore, a degree on the Fahrenheit scale is 1⁄180 of the interval between the freezing point and the boiling point. On the Celsius scale, the freezing and boiling points of water are 100 degrees apart, a temperature interval of 1 °F is equal to an interval of 5⁄9 degrees Celsius. The Fahrenheit and Celsius scales intersect at −40°, absolute zero is −273.15 °C or −459.67 °F. For an exact conversion, the formulas can be applied. Again, f is the value in Fahrenheit and c the value in Celsius, f °Fahrenheit to c °Celsius, C °Celsius to f °Fahrenheit, −40 = f. Fahrenheit proposed his temperature scale in 1724, basing it on two points of temperature. In his initial scale, the point is determined by placing the thermometer in a mixture of ice, water. This is a mixture which stabilizes its temperature automatically, that stable temperature was defined as 0 °F. The second point,96 degrees, was approximately the human bodys temperature, in any case, the definition of the Fahrenheit scale has changed since. According to a letter Fahrenheit wrote to his friend Herman Boerhaave, his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømers scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, Fahrenheit multiplied each value by four in order to eliminate fractions and increase the granularity of the scale. Fahrenheit observed that water boils at about 212 degrees using this scale, under this system, the Fahrenheit scale is redefined slightly so that the freezing point of water is exactly 32 °F, and the boiling point is exactly 212 °F or 180 degrees higher. It is for this reason that human body temperature is approximately 98° on the revised scale
Fahrenheit
–
Thermometer with Fahrenheit and Celsius units
Fahrenheit
–
Daniel Gabriel Fahrenheit
7.
Relative permittivity
–
The relative permittivity of a material is its permittivity expressed as a ratio relative to the permittivity of vacuum. Permittivity is a property that affects the Coulomb force between two point charges in the material. Relative permittivity is the factor by which the field between the charges is decreased relative to vacuum. Likewise, relative permittivity is the ratio of the capacitance of a capacitor using that material as a dielectric, relative permittivity is also commonly known as dielectric constant, a term deprecated in physics and engineering as well as in chemistry. Relative permittivity is typically denoted as εr and is defined as ε r = ε ε0, where ε is the complex frequency-dependent absolute permittivity of the material, and ε0 is the vacuum permittivity. Relative permittivity is a number that is in general complex-valued, its real and imaginary parts are denoted as. The relative permittivity of a medium is related to its electric susceptibility, χe, in anisotropic media the relative permittivity is a second rank tensor. The relative permittivity of a material for a frequency of zero is known as its relative permittivity. The historical term for the relative permittivity is dielectric constant and it is still commonly used, but has been deprecated by standards organizations, because of its ambiguity, as some older authors used it for the absolute permittivity ε. The permittivity may be quoted either as a property or as a frequency-dependent variant. It has also used to refer to only the real component εr of the complex-valued relative permittivity. In the causal theory of waves, permittivity is a complex quantity, the imaginary part corresponds to a phase shift of the polarization P relative to E and leads to the attenuation of electromagnetic waves passing through the medium. By definition, the relative permittivity of vacuum is equal to 1. The relative static permittivity, εr, can be measured for static electric fields as follows, first the capacitance of a test capacitor, then, using the same capacitor and distance between its plates, the capacitance Cx with a dielectric between the plates is measured. The relative dielectric constant can be calculated as ε r = C x C0. For time-variant electromagnetic fields, this quantity becomes frequency-dependent, an indirect technique to calculate εr is conversion of radio frequency S-parameter measurement results. A description of frequently used S-parameter conversions for determination of the frequency-dependent εr of dielectrics can be found in this bibliographic source, alternatively, resonance based effects may be employed at fixed frequencies. The relative permittivity is a piece of information when designing capacitors
Relative permittivity
–
Temperature dependence of the relative static permittivity of water
8.
Jagiellonian University
–
The Jagiellonian University is a research university in Kraków, Poland. Notable alumni include, among others, mathematician and astronomer Nicolaus Copernicus, Polish king John III Sobieski, pope John Paul II, the campus of the Jagiellonian University is centrally located within the city of Kraków. The university consists of fifteen faculties — including the humanities, law, the natural and social sciences, the university employs roughly 4,000 academics, and has more than 40,000 students who study in some 80 disciplines. More than half of the student body are women, the language of instruction is usually Polish, although several degrees are offered in either German or English. The university library is one of Polands largest, and houses several medieval manuscripts, due to its history, the Jagiellonian University is traditionally considered Polands most reputable institution of higher learning — this standing equally being reflected in international rankings. The Jagiellonian University is a member of the Coimbra Group and Europaeum and his efforts to found an institution of higher learning in Poland were rewarded when Pope Urban V granted him permission to set up a university in Kraków. A royal charter of foundation was issued on 12 May 1364, and it is believed that, in all likelihood, the construction of a building to house the Studium Generale began on Plac Wolnica in what is today the district of Kazimierz. After a period of disinterest and lack of funds, the institution was restored in the 1390s by King Władysław II Jagiełło and his wife Saint Hedwig, the Queen donated all of her personal jewelry to the university, allowing it to enroll 203 students. The university was the first university in Europe to establish independent chairs in Mathematics, during the second half of the 15th century, over 40 percent of students came from outside the Kingdom of Poland. The first chancellor of the University was Piotr Wysz, and the first professors were Czechs, Germans and Poles, by 1520 Greek philology was introduced by Constanzo Claretti and Wenzel von Hirschberg, Hebrew was also taught. At this time, the Collegium Maius comprised seven reading rooms, six of which were named for the ancient scholars, Aristotle, Socrates, Plato, Galen, Ptolemy. The librarys original rooms, in all books were chained to their cases in order to prevent theft, are no longer used as such. However, they are occasionally opened to host visiting lecturers talks. If the lecture halls underwent refurbishment they could be rented out to accommodate a laundry and this period thus represents one of the darkest periods in the universitys history and is almost certainly the one during which the closure of the institution seemed most imminent. After the third partition of Poland in 1795 and the ensuing Napoleonic Wars, Kraków became a city under the protection of the Austrian Empire. In 1846, after the Kraków Uprising, the city and its university became part of the Austrian Empire, however, the threat of closure of the University was ultimately dissipated by Kaiser Ferdinand I of Austrias decree to maintain it. By the 1870s the fortunes of the university had improved so greatly that many scholars had returned, the liquefaction of nitrogen and oxygen was successfully demonstrated by professors Zygmunt Wróblewski and Karol Olszewski in 1883. It was, conversely, from this building that in 1918 a large painting of Kaiser Franz Joseph was removed and destroyed by Polish students advocating the reestablishment of an independent Polish state
Jagiellonian University
–
The founding of the University in 1364 AD, painted by
Jan Matejko (1838–1893).
Jagiellonian University
–
Jagiellonian University
Jagiellonian University
–
The Collegium Maius dates from shortly after the university's establishment
Jagiellonian University
–
The main assembly hall of the university's Collegium Maius
9.
Karol Olszewski
–
Karol Stanisław Olszewski was a Polish chemist, mathematician and physicist. Olszewski was a graduate of Kazimierz Brodziński High School in Tarnów and he studied at Krakóws Jagiellonian University in the departments of mathematics and physics, and chemistry and biology. He carried out his first experiments using an improved compressor. Olszewski defended his dissertation at Heidelberg University, then returned to Kraków. In 1883, Zygmunt Wróblewski and Karol Olszewski were the first in the world to liquefy oxygen, nitrogen, in 1884, in his Kraków laboratory, Olszewski was the first to liquefy hydrogen in a dynamic state, achieving a record low temperature of −225 °C. He failed only to liquefy then-newly discovered helium, in 1896, on hearing of Wilhelm Röntgens work with X-rays, within a few days in early February Olszewski replicated it, thus initiating the universitys department of radiology. Timeline of low-temperature technology Timeline of hydrogen technologies List of Poles Olszewski, Karol Stanisław, Encyklopedia Polski, p.464
Karol Olszewski
–
Karol Olszewski
Karol Olszewski
–
Inscription in
Polish and
Latin: "In this building Karol Olszewski [and]
Zygmunt Wróblewski professors at
Jagiellonian University in 1883 for the first time in the world liquifed components of air thereby opening to science and industry new fields of research and application"
10.
Fractional distillation
–
Generally the component parts have boiling points that differ by less than 25 °C from each other under a pressure of one atmosphere. If the difference in boiling points is greater than 25 °C, heat source, such as a hot plate with a bath, and ideally with a magnetic stirrer. g. As an example consider the distillation of a mixture of water, ethanol boils at 78.4 °C while water boils at 100 °C. So, by heating the mixture, the most volatile component will concentrate to a degree in the vapor leaving the liquid. Some mixtures form azeotropes, where the mixture boils at a lower temperature than either component, in this example, a mixture of 96% ethanol and 4% water boils at 78.2 °C, the mixture is more volatile than pure ethanol. For this reason, ethanol cannot be purified by direct fractional distillation of ethanol-water mixtures. The apparatus is assembled as in the diagram, the mixture is put into the round bottomed flask along with a few anti-bumping granules, and the fractionating column is fitted into the top. The fractional distillation column is set up with the source at the bottom on the still pot. As the distance from the stillpot increases, a gradient is formed in the column, it is coolest at the top. As the mixed vapor ascends the temperature gradient, some of the vapor condenses and revaporizes along the temperature gradient, each time the vapor condenses and vaporizes, the composition of the more volatile component in the vapor increases. This distills the vapor along the length of the column, the vapor condenses on the glass platforms, known as trays, inside the column, and runs back down into the liquid below, refluxing distillate. The hottest tray is at the bottom and the coolest is at the top, at steady state conditions, the vapor and liquid on each tray are at equilibrium. The most volatile component of the exits as a gas at the top of the column. The vapor at the top of the column then passes into the condenser, the process continues until all the ethanol boils out of the mixture. This point can be recognized by the rise in temperature shown on the thermometer. The above explanation reflects the theoretical way fractionation works, normal laboratory fractionation columns will be simple glass tubes filled with a packing, often small glass helices of 4 to 7 mm diameter. Such a column can be calibrated by the distillation of a known mixture system to quantify the column in terms of number of theoretical trays, in laboratory distillation, several types of condensers are commonly found. The Liebig condenser is simply a tube within a water jacket
Fractional distillation
–
Typical industrial fractional distillation columns
Fractional distillation
–
Fractional distillation An
Erlenmeyer flask is used as a receiving flask. Here the distillation head and
fractionating column are combined in one piece.
11.
Covalent bond
–
A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, for many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, the term covalent bond dates from 1939. In the molecule H2, the atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities, thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electronegativity. Covalent bonding that entails sharing of electrons more than two atoms is said to be delocalized. The term covalence in regard to bonding was first used in 1919 by Irving Langmuir in a Journal of the American Chemical Society article entitled The Arrangement of Electrons in Atoms and Molecules. Langmuir wrote that we shall denote by the term covalence the number of pairs of electrons that an atom shares with its neighbors. The idea of covalent bonding can be traced several years before 1919 to Gilbert N. Lewis and he introduced the Lewis notation or electron dot notation or Lewis dot structure, in which valence electrons are represented as dots around the atomic symbols. Pairs of electrons located between atoms represent covalent bonds, multiple pairs represent multiple bonds, such as double bonds and triple bonds. An alternative form of representation, not shown here, has bond-forming electron pairs represented as solid lines, Lewis proposed that an atom forms enough covalent bonds to form a full outer electron shell. In the diagram of methane shown here, the atom has a valence of four and is, therefore, surrounded by eight electrons, four from the carbon itself. Each hydrogen has a valence of one and is surrounded by two electrons – its own one electron plus one from the carbon, walter Heitler and Fritz London are credited with the first successful quantum mechanical explanation of a chemical bond in 1927. Their work was based on the valence bond model, which assumes that a bond is formed when there is good overlap between the atomic orbitals of participating atoms. Atomic orbitals have specific directional properties leading to different types of covalent bonds, sigma bonds are the strongest covalent bonds and are due to head-on overlapping of orbitals on two different atoms. A single bond is usually a σ bond, pi bonds are weaker and are due to lateral overlap between p orbitals. A double bond between two given atoms consists of one σ and one π bond, and a bond is one σ. Covalent bonds are also affected by the electronegativity of the atoms which determines the chemical polarity of the bond
Covalent bond
–
Early concepts in covalent bonding arose from this kind of image of the molecule of
methane. Covalent bonding is implied in the
Lewis structure by indicating electrons shared between atoms.
12.
Liquefaction
–
Liquefaction occurs both as part of natural processes, and in man-made processes used in science and commerce. In geology, soil liquefaction refers to the process by which water-saturated, unconsolidated sediments are transformed into a substance that acts like a liquid, by undermining the foundations and base courses of infrastructure, liquefaction can cause serious damage. In physics and chemistry, the transitions from solid and gas to liquid may be referred to as liquefaction. The melting point is the temperature and pressure at which a solid becomes a liquid, in commercial and industrial situations, the process of condensing a gas to liquid is sometimes referred to as liquefaction of gases. Coal liquefaction is the production of fuels from coal using a variety of industrial processes. Liquefaction is also used in commercial and industrial settings to refer to mechanical dissolution of a solid by mixing, grinding or blending with a liquid. In kitchen or laboratory settings, solids may be chopped into smaller parts sometimes in combination with a liquid and this may be done with a blender, or liquidiser in British English. In biology, liquefaction often involves organic tissue turning into a more liquid-like state, for example, liquefactive necrosis in pathology, or liquefaction as a parameter in semen analysis
Liquefaction
–
The effects of
soil liquefaction, seen after
2011 Canterbury earthquake
13.
Cryogenics
–
In physics, cryogenics is the study of the production and behaviour of materials at very low temperatures. It is not well-defined at what point on the temperature scale refrigeration ends and cryogenics begins, but scientists assume a gas to be cryogenic if it can be liquefied at or below −150 °C. The U. S. National Institute of Standards and Technology has chosen to consider the field of cryogenics as that involving temperatures below −180 °C or −292.00 °F or 93.15 K. A person who studies elements that have been subjected to cold temperatures is called a cryogenicist. Cryogenicists use the Kelvin or Rankine temperature scales present in nature, Cryogenics The branches of physics and engineering that involve the study of very low temperatures, how to produce them, and how materials behave at those temperatures. Cryobiology The branch of biology involving the study of the effects of low temperatures on organisms, cryoconservation of animal genetic resources The conservation of genetic material with the intention of conserving a breed. Cryosurgery The branch of surgery applying very low temperatures to destroy malignant tissue, cryoelectronics The field of research regarding superconductivity at low temperatures. Cryotronics The practical application of cryoelectronics, Cryonics Cryopreserving humans and animals with the intention of future revival. Cryogenics is sometimes used to mean Cryonics in popular culture. The word cryogenics stems from Greek kρύο – cold + genic – having to do with production, Cryogenic fluids with their boiling point in kelvins Liquefied gases, such as liquid nitrogen and liquid helium, are used in many cryogenic applications. Liquid nitrogen is the most commonly used element in cryogenics and is legally purchasable around the world, Liquid helium is also commonly used and allows for the lowest attainable temperatures to be reached. These liquids may be stored in Dewar flasks, which are double-walled containers with a vacuum between the walls to reduce heat transfer into the liquid. Typical laboratory Dewar flasks are spherical, made of glass and protected in a metal outer container, Dewar flasks for extremely cold liquids such as liquid helium have another double-walled container filled with liquid nitrogen. Dewar flasks are named after their inventor, James Dewar, the man who first liquefied hydrogen, thermos bottles are smaller vacuum flasks fitted in a protective casing. Cryogenic barcode labels are used to mark dewar flasks containing these liquids, Cryogenic transfer pumps are the pumps used on LNG piers to transfer liquefied natural gas from LNG carriers to LNG storage tanks, as are cryogenic valves. The field of cryogenics advanced during World War II when scientists found that metals frozen to low temperatures showed more resistance to wear, based on this theory of cryogenic hardening, the commercial cryogenic processing industry was founded in 1966 by Ed Busch. This evolved in the late 1990s into the treatment of other parts, cryogens, such as liquid nitrogen, are further used for specialty chilling and freezing applications. Some chemical reactions, like those used to produce the active ingredients for the popular statin drugs, special cryogenic chemical reactors are used to remove reaction heat and provide a low temperature environment
Cryogenics
–
Liquid nitrogen
Cryogenics
–
Astronomical instruments on the
Very Large Telescope are equipped with continuous flow cooling systems.
Cryogenics
–
Cryogenic gases delivery truck at a supermarket,
Ypsilanti, Michigan
14.
Freezing
–
Freezing, or solidification, is a phase transition in which a liquid turns into a solid when its temperature is lowered below its freezing point. For most substances, the melting and freezing points are the temperature, however. For example, agar displays a hysteresis in its melting point and it melts at 85 °C and solidifies from 32 °C to 40 °C. Most liquids freeze by crystallization, formation of crystalline solid from the uniform liquid, because of the latent heat of fusion, the freezing is greatly slowed down and the temperature will not drop anymore once the freezing starts but will continue dropping once it finishes. Crystallization consists of two events, nucleation and crystal growth. Nucleation is the step wherein the molecules start to gather into clusters, on the scale, arranging in a defined. The crystal growth is the subsequent growth of the nuclei that succeed in achieving the critical cluster size, in spite of the second law of thermodynamics, crystallization of pure liquids usually begins at a lower temperature than the melting point, due to high activation energy of homogeneous nucleation. The creation of a nucleus implies the formation of an interface at the boundaries of the new phase, some energy is expended to form this interface, based on the surface energy of each phase. If a hypothetical nucleus is too small, the energy that would be released by forming its volume is not enough to create its surface, Freezing does not start until the temperature is low enough to provide enough energy to form stable nuclei. Under high pressure water will super cool to as low as −70 °C before freezing, Freezing is almost always an exothermic process, meaning that as liquid changes into solid, heat and pressure is released. This is often seen as counter-intuitive, since the temperature of the material does not rise during freezing, but this can be understood, since heat must be continually removed from the freezing liquid or the freezing process will stop. The energy released upon freezing is a latent heat, and is known as the enthalpy of fusion and is exactly the same as the required to melt the same amount of the solid. Low-temperature helium is the only exception to the general rule. Helium-3 has an enthalpy of fusion at temperatures below 0.3 K. Helium-4 also has a very slightly negative enthalpy of fusion below 0.8 K. This means that, at appropriate constant pressures, heat must be added to these substances in order to freeze them, certain materials, such as glass and glycerol, may harden without crystallizing, these are called amorphous solids. Amorphous materials as well as some polymers do not have a freezing point, instead, there is a gradual change in their viscoelastic properties over a range of temperatures. Such materials are characterized by a transition that occurs at a glass transition temperature. Because vitrification is a process, it does not qualify as freezing
Freezing
15.
Thermal insulation
–
Thermal insulation is the reduction of heat transfer between objects in thermal contact or in range of radiative influence. Thermal insulation can be achieved with specially engineered methods or processes, as well as with suitable object shapes, heat flow is an inevitable consequence of contact between objects of differing temperature. Thermal insulation provides a region of insulation in which thermal conduction is reduced or thermal radiation is reflected rather than absorbed by the lower-temperature body, the insulating capability of a material is measured with thermal conductivity. Low thermal conductivity is equivalent to high insulating capability, in thermal engineering, other important properties of insulating materials are product density and specific heat capacity. Solid materials chosen for insulation have a low thermal conductivity k, as the thickness of insulation is increased, the thermal resistance also increases. For insulated cylinders, a critical radius must be reached, before the critical radius is reached any added insulation increases heat transfer. If the outside radius of a cylinder is increased by applying insulation, however, at the same time, the convective resistance is reduced. This implies that adding insulation below a critical radius actually increases the heat transfer. If the radius of the cylinder is smaller than the critical radius for insulation. Gases possess poor thermal conduction properties compared to liquids and solids, in order to further augment the effectiveness of a gas it may be disrupted into small cells which cannot effectively transfer heat by natural convection. Convection involves a larger flow of gas driven by buoyancy and temperature differences. In order to accomplish gas cell formation in man-made thermal insulation, glass and this principle is used industrially in building and piping insulation such as, cellulose, rock wool, polystyrene foam, urethane foam, vermiculite, perlite, and cork. Trapping air is also the principle in all highly insulating clothing materials such as wool, down feathers, the air-trapping property is also the insulation principle employed by homeothermic animals to stay warm, for example down feathers, and insulating hair such as natural sheeps wool. In both cases the primary insulating material is air, and the used for trapping the air is natural keratin protein. Maintaining acceptable temperatures in buildings uses a proportion of global energy consumption. For a period of time, Asbestos was also used, however, when well insulated, a building, is energy-efficient, thus saving the owner money. Provides more uniform throughout the space. Unlike heating and cooling equipment, insulation is permanent and does not require maintenance, upkeep, lowers the carbon footprint of a building
Thermal insulation
–
Mineral wool Insulation, 1600 dpi scan
Thermal insulation
–
Car exhausts usually require some form of heat barrier, especially high performance exhausts where a ceramic coating is often applied
Thermal insulation
–
Common insulation applications in
apartment building in
Ontario,
Canada.
Thermal insulation
–
Thermal insulation applied to exhaust component by means of plasma spraying
16.
Heat
–
WWE Heat was a professional wrestling television program produced by World Wrestling Entertainment. Heat was most recently streamed on WWE. com on Friday afternoons for North American viewers, the final episode was uploaded to WWE. com. The show was replaced internationally with WWE Vintage Collection, a program featuring classic matches, the show was originally introduced on the USA Network on August 2,1998 in the United States. The one-hour show would be broadcast on Sunday nights, it would be live most weeks and it was the second primary program of the WWFs weekly television show line-up, serving as a supplement to the Monday Night Raw program. On scheduled WWF pay-per-view event nights, Heat would also serve as a show to the events. The show was signed for only 6 episodes but was very popular and was continued. With the premiere of SmackDown. in August 1999, coverage of Heat was significantly reduced in favor of the newer show, also led to Heat being taped before SmackDown. With matches for WWF syndication programs like Jakked/Metal being taped before Raw broadcasts, premiered, also Heat briefly became a complete weekly summary show, featuring occasional interviews and music videos. After only a few weeks following the change, Heat began airing exclusive matches again. Occasionally, special editions of the show aired heavily promoted, for Super Bowl XXXIII in 1999, Heat aired as Halftime Heat on the USA Network during halftime of the Super Bowl. These specials ended following the move to MTV in 2000. When the show started airing on MTV in late 2000, it was broadcast live from WWF New York, WWF personalities and performers would appear at the restaurant as special guests while Michael Cole and Tazz provided commentary to matches. The United Kingdoms coverage of Heat began in January 2000, when Channel 4 started broadcasting the show at 4pm on Sundays and these one-hour shows were a magazine-type show, usually featuring three or four brief matches as well as highlights from Raw and SmackDown. Were aired on this version of the show, a separate commentary team was used on airings in the United Kingdom, with references aimed more at that specific audience. The two-person announce team was a mix of individuals including Kevin Kelly, Michael Cole, Michael Hayes, during the middle of 2000, Heat started to get moved around the Channel 4 schedule, usually between the afternoon and midnight. Towards the end of 2000, the show was moved to being broadcast in the early-hours of Monday mornings. The show stayed in the time-slot until December 2001 when Channel 4s deal with the World Wrestling Federation expired in the United Kingdom, in April 2002, the show returned to its original filming schedule, again before Raw. Eventually, the live from WWF New York format was retired, ratings were still moderate for Heat, although the show lost some popularity once SmackDown
Heat
–
Heat logo used from October 1, 2000 - May 30, 2008
Heat
Heat
–
Sunday Night Heat logo used from August 2, 1998 to September 24, 2000
Heat
–
The Heat version of the universal WWE entrance set introduced in January 2008 for WWE's
high-def broadcasting.
17.
Vacuum flasks
–
A vacuum flask is an insulating storage vessel that greatly lengthens the time over which its contents remain hotter or cooler than the flasks surroundings. Invented by Sir James Dewar in 1892, the vacuum consists of two flasks, placed one within the other and joined at the neck. The gap between the two flasks is partially evacuated of air, creating a near-vacuum which significantly reduces heat transfer by conduction or convection, Vacuum flasks are used domestically to keep beverages hot or cold for extended periods of time and for many purposes in industry. The vacuum flask was designed and invented by Scottish scientist Sir James Dewar in 1892 as a result of his research in the field of cryogenics and is called a Dewar flask in his honour. He evacuated the air between the two creating a partial vacuum to keep the temperature of the contents stable. Through the need for this insulated container James Dewar created the vacuum flask, the flask was later developed using new materials such as glass and aluminum, however, Dewar refused to patent his invention. Prior to Dewars invention, German chemist and physician Adolf Ferdinand Weinhold invented his own version of a flask in 1881. Dewars design was transformed into a commercial item in 1904 as two German glassblowers discovered that it could be used to keep cold drinks cold and warm drinks warm. The name later became a trademark after the term thermos became the household name for such a liquid container. The vacuum flask went on to be used for different types of scientific experiments. Thermos remains a trademark in some countries but was declared a genericized trademark in the US in 1963 since it is colloquially synonymous with vacuum flasks in general. However, there are other vacuum flasks, after the German glassblowers determined the commercial uses for the Dewar flask, the technology was sold to the Thermos company who used it to mass-produce vacuum flasks for at-home use. Eventually other manufacturers produced similar products for consumer use, the vacuum flask consists of two flasks, placed one within the other and joined at the neck. The gap between the two flasks is partially evacuated of air, creating a partial-vacuum which reduces heat conduction or convection, most heat transfer occurs through the neck and opening of the flask, where there is no vacuum. Vacuum flasks are made of metal, borosilicate glass, foam or plastic and have their opening stoppered with cork or polyethylene plastic. Vacuum flasks are used as insulated shipping containers. Extremely large or long vacuum flasks sometimes cannot fully support the inner flask from the neck alone and these spacers act as a thermal bridge and partially reduce the insulating properties of the flask around the area where the spacer contacts the interior surface. Several technological applications, such as NMR and MRI machines, rely on the use of vacuum flasks
Vacuum flasks
–
The typical design of a Thermos brand vacuum flask, used for maintaining the temperature of fluids such as
coffee.
Vacuum flasks
–
Laboratory Dewar flask,
Deutsches Museum, Munich
Vacuum flasks
–
A
cryogenic storage dewar of
liquid nitrogen, used to supply a
cryogenic freezer
Vacuum flasks
–
From Weinhold 1881 described vacuum flask
18.
Cryogenic storage dewar
–
A cryogenic storage dewar is a specialised type of vacuum flask used for storing cryogens, whose boiling points are much lower than room temperature. Cryogenic storage dewars may take different forms including open buckets, flasks with loose-fitting stoppers. All dewars have walls constructed from two or more layers, with a high vacuum maintained between the layers and this provides very good thermal insulation between the interior and exterior of the dewar, which reduces the rate at which the contents boil away. Precautions are taken in the design of dewars to safely manage the gas which is released as the liquid slowly boils, the simplest dewars allow the gas to escape either through an open top or past a loose-fitting stopper to prevent the risk of explosion. More sophisticated dewars trap the gas above the liquid, and hold it at high pressure and this increases the boiling point of the liquid, allowing it to be stored for extended periods. Excessive vapour pressure is released automatically through safety valves, the method of decanting liquid from a dewar depends upon its design. Simple dewars may be tilted, to pour liquid from the neck, self-pressurising designs use the gas pressure in the top of the dewar to force the liquid upward through a pipe leading to the neck. Cryogens present several safety hazards and storage vessels are designed to reduce the associated risk, firstly, no dewar can provide perfect thermal insulation and the cryogenic liquid slowly boils away, which yields an enormous quantity of gas. In dewars with a top, the gas simply escapes into the surrounding area. However, very high pressures can build up inside sealed dewars, one or more pressure-relief valves allow gas to vent away from the dewar whenever the pressure becomes excessive. In an incident in 2006 at Texas A&M University, the devices of a tank of liquid nitrogen were sealed with brass plugs. As a result, the tank failed catastrophically and exploded, ice can form on the inside of the dewar if it is left open to the air for extended periods. This can be dangerous as the openings of the dewar can become blocked, leading to a pressure build-up. The gas escaping from a dewar can gradually displace the oxygen from the air in the surrounding area, which presents an asphyxiation hazard
Cryogenic storage dewar
–
A self-pressurising dewar (silver, foreground) being filled with
liquid nitrogen from a large storage tank (white, background).
19.
Leidenfrost effect
–
Due to this repulsive force, a droplet hovers over the surface rather than making physical contact with it. The effect is responsible for the ability of liquid nitrogen to skitter across floors. The latter is potentially lethal, particularly should one accidentally swallow the liquid nitrogen and it is named after Johann Gottlob Leidenfrost, who discussed it in A Tract About Some Qualities of Common Water in 1756. The effect can be seen as drops of water are sprinkled onto a pan at various times as it heats up. Initially, as the temperature of the pan is just below 100 °C, the water out and slowly evaporates, or if the temperature of the pan is well below 100 °C. As the temperature of the pan goes above 100 °C, the water droplets hiss when touching the pan, later, as the temperature exceeds the Leidenfrost point, the Leidenfrost effect comes into play. On contact with the pan, the water droplets bunch up into balls of water and skitter around. This effect works until a higher temperature causes any further drops of water to evaporate too quickly to cause this effect. This is because at temperatures above the Leidenfrost point, the part of the water droplet vaporizes immediately on contact with the hot plate. The resulting gas suspends the rest of the water droplet just above it, as steam has much poorer thermal conductivity, further heat transfer between the pan and the droplet is slowed down dramatically. This also results in the drop being able to skid around the pan on the layer of gas just under it, the temperature at which the Leidenfrost effect begins to occur is not easy to predict. Some research has been conducted into a model of the system. As a very rough estimate, the Leidenfrost point for a drop of water on a frying pan might occur at 193 °C. In a pair of lectures on design, he cited the work of Pierre Hippolyte Boutigny and Professor Bowman of Kings College. A drop of water that was vaporized almost immediately at 168 °C persisted for 152 seconds at 202 °C, lower temperatures in a boiler firebox might evaporate water more quickly as a result, compare Mpemba effect. An alternative approach was to increase the temperature beyond the Leidenfrost point, fairbairn considered this too, and may have been contemplating the flash steam boiler, but considered the technical aspects insurmountable for the time. The Leidenfrost point may also be taken to be the temperature for which the hovering droplet lasts longest and it has been demonstrated that it is possible to stabilize the Leidenfrost vapour layer of water by exploiting superhydrophobic surfaces. In this case, once the layer is established, cooling never collapses the layer, and no nucleate boiling occurs
Leidenfrost effect
–
A water droplet experiencing Leidenfrost effect on a hot stove plate
Leidenfrost effect
–
Leidenfrost droplet
Leidenfrost effect
–
Reactive Leidenfrost Effect of Cellulose on Silica, 750° C (~1400° Fahrenheit)
20.
Freezing point
–
The melting point of a solid is the temperature at which it changes state from solid to liquid at atmospheric pressure. At the melting point the solid and liquid phase exist in equilibrium, the melting point of a substance depends on pressure and is usually specified at standard pressure. When considered as the temperature of the change from liquid to solid. Because of the ability of some substances to supercool, the point is not considered as a characteristic property of a substance. For most substances, melting and freezing points are approximately equal, for example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures, for example, agar melts at 85 °C and solidifies from 31 °C to 40 °C, such direction dependence is known as hysteresis. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances the freezing point of water is the same as the melting point, the chemical element with the highest melting point is tungsten, at 3687 K, this property makes tungsten excellent for use as filaments in light bulbs. Many laboratory techniques exist for the determination of melting points, a Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip revealing its thermal behaviour at the temperature at that point, differential scanning calorimetry gives information on melting point together with its enthalpy of fusion. A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window, the several grains of a solid are placed in a thin glass tube and partially immersed in the oil bath. The oil bath is heated and with the aid of the melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, the measurement can also be made continuously with an operating process. For instance, oil refineries measure the point of diesel fuel online, meaning that the sample is taken from the process. This allows for more frequent measurements as the sample does not have to be manually collected, for refractory materials the extremely high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees, the spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source that has been previously calibrated as a function of temperature, in this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer, for temperatures above the calibration range of the source, an extrapolation technique must be employed
Freezing point
–
Melting points (in blue) and boiling points (in pink) of the first eight
carboxylic acids (°C)
Freezing point
–
Kofler bench with samples for calibration
Freezing point
–
Automatic digital melting point meter
Freezing point
–
Pressure dependence of water melting point
21.
Refrigerant
–
A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas, many working fluids have been used for such purposes. Fluorocarbons, especially chlorofluorocarbons, became commonplace in the 20th century, other common refrigerants used in various applications are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as propane. The ideal refrigerant would have favorable properties, be noncorrosive to mechanical components. It would not cause ozone depletion or climate change, since different fluids have the desired traits in different degree, choice is a matter of trade-off. Since boiling point and gas density are affected by pressure, refrigerants may be more suitable for a particular application by choice of operating pressures. In order from the highest to the lowest potential of ozone depletion are Bromochlorofluorocarbon, though HFC and PFC are non-ozone depleting, many have global warming potentials that are thousands of times greater than CO2. Some other refrigerants such as propane and ammonia are not inert, new refrigerants were developed in the early 21st century that are safer for the environment, but their application has been held up due to concerns over toxicity and flammability. Early mechanical refrigeration systems employed sulfur dioxide, methyl chloride and ammonia, being toxic, sulfur dioxide and methyl chloride rapidly disappeared from the market with the introduction of CFCs. Occasionally, one may encounter older machines with methyl formate, chloromethane, chlorofluorocarbons were little used for refrigeration until better synthesis methods, developed in the 1950s, reduced their cost. Their domination of the market was called into question in the 1980s by concerns about depletion of the ozone layer and they are currently subject to prohibition discussions on account of their harmful effect on the climate. In 1997, FCs and HFCs were included in the Kyoto Protocol to the Framework Convention on Climate Change, in 2006, the EU adopted a Regulation on fluorinated greenhouse gases, which makes stipulations regarding the use of FCs and HFCs with the intention of reducing their emissions. The provisions do not affect climate-neutral refrigerants, refrigerants such as ammonia, carbon dioxide and non-halogenated hydrocarbons do not deplete the ozone layer and have no or only a low global warming potential. They are used in air-conditioning systems for buildings, in sport and leisure facilities, in the industry, in the automotive industry. In these settings their toxicity is less a concern than in home equipment, emissions from automobile air conditioning are a growing concern because of their impact on climate change. From 2011 on, the European Union will phase out refrigerants with a global warming potential of more than 150 in automotive air conditioning and this will ban potent greenhouse gases such as the refrigerant HFC-134a —which has a GWP of 1410—to promote safe and energy-efficient refrigerants. One of the most promising alternatives is CO2, carbon dioxide is non-flammable, non-ozone depleting, has a global warming potential of 1. R-744 can be used as a fluid in climate control systems for cars, residential air conditioning, hot water pumps, commercial refrigeration
Refrigerant
–
R407C
pressure -
enthalpy diagram, isotherms between the two saturation lines
22.
Cryotherapy
–
Cryotherapy is the local or general use of low temperatures in medical therapy. Cryotherapy is used to treat a variety of benign and malignant tissue damage, the term cryotherapy comes from the Greek cryo meaning cold, and therapy meaning cure. Cryotherapy has been used as early as the seventeenth century, the most prominent use of the term refers to the surgical treatment, specifically known as cryosurgery. Other therapies that use the term are whole-body cryotherapy and ice pack therapy, cryosurgery is the application of extreme cold to destroy abnormal or diseased tissue. Cryosurgery is used to treat a number of diseases and disorders, most especially skin conditions like warts, moles, skin tags, liquid nitrogen is usually used to freeze the tissues at the cellular level. The procedure is used often because of its efficacy and a low rate of side effects, ice pack therapy is a treatment of cold temperatures to an injured area of the body. An ice pack is placed over an area and is intended to absorb heat of a closed traumatic or edematous injury by using conduction to transfer thermal energy. The physiologic effects of application include immediate vasoconstriction with reflexive vasodilation, decreased local metabolism and enzymatic activity. Cold decreases muscle spindle fiber activity and slows nerve conduction velocity, therefore it is used to decrease spasticity. It is commonly used to alleviate the pain of minor injuries, the use of ice packs in treatment decreases the blood flow most rapidly at the beginning of the cooling period, this occurs as a result of vasoconstriction, the initial reflex sympathetic activity. However, if ice pack therapy is applied for less than 10 minutes, if the ice bag therapy is removed at this time, sportsmen are sent back to training or competition directly with no decrease in performance. Whole body cryotherapy is an alternative to cold water immersion or ice packs and this treatment involves exposing individuals to extremely cold dry air for two to four minutes. To achieve the temperatures required for WBC, two methods are typically used, liquid nitrogen and refrigerated cold air. During these exposures, individuals wear minimal clothing, which consists of shorts for males and shorts. Gloves, a woollen headband covering the ears, and a nose and mouth mask, in addition to dry shoes and socks, are commonly worn to reduce the risk of cold-related injury. The first WBC chamber was built in Japan in the late 1970s, but WBC was not introduced to Europe until the 1980s, recently, recreational athletes have started to emulate elite athletes in using these treatments after exercise. Consequently, WBC may be effective in relieving soreness, or muscle pain, through reduced muscle metabolism, skin microcirculation, receptor sensitivity, interestingly, a paradoxical increase in rectal temperature, followed by a slight decline, has been reported following exposure to the treatment. There is also a body of evidence to suggest that WBC stimulates the nervous system, with a predominance of parasympathetic tone activation
Cryotherapy
–
Medical cryotherapy gun
Cryotherapy
–
Cryo chamber at −110 °C
Cryotherapy
–
Cryo therapy patients during preparation of treatment of ca. 3 minutes
23.
Cryophorus
–
A cryophorus is a glass container containing liquid water and water vapor. It is used in courses to demonstrate rapid freezing by evaporation. A typical cryophorus has a bulb at one end connected to a tube of the same material, when the liquid water is manipulated into the bulbed end and the other end is submerged into a freezing mixture, the gas pressure drops as it is cooled. The liquid water begins to evaporate, producing water vapor. Evaporation causes the water to cool rapidly to its freezing point, the cryophorus was first described by William Hyde Wollaston in an 1811 paper titled, On a method of freezing at a distance. Smith, B. A. Wollastons cryophosphorus-precursor of the heat pipe
Cryophorus
–
A diagram of a cryophorus showing water evaporating from the left bulb and condensing and freezing in the right bulb.
24.
Evaporation
–
Evaporation is a type of vaporization of a liquid that occurs from the surface of a liquid into a gaseous phase that is not saturated with the evaporating substance. The other type of vaporization is boiling, which is characterized by bubbles of saturated vapor forming in the liquid phase, steam produced in a boiler is another example of evaporation occurring in a saturated vapor phase. Evaporation that occurs directly from the solid phase below the melting point, on average, a fraction of the molecules in a glass of water have enough heat energy to escape from the liquid. The water in the glass will be cooled by the evaporation until an equilibrium is reached where the air supplies the amount of heat removed by the evaporating water, in an enclosed environment the water would evaporate until the air is saturated. With sufficient temperature, the liquid would turn into vapor quickly, when the molecules collide, they transfer energy to each other in varying degrees, based on how they collide. Sometimes the transfer is so one-sided for a molecule near the surface that it ends up with energy to escape. Evaporation is an part of the water cycle. The sun drives evaporation of water from oceans, lakes, moisture in the soil, in hydrology, evaporation and transpiration are collectively termed evapotranspiration. Evaporation of water occurs when the surface of the liquid is exposed, allowing molecules to escape and form water vapor, when only a small proportion of the molecules meet these criteria, the rate of evaporation is low. Since the kinetic energy of a molecule is proportional to its temperature, as the faster-moving molecules escape, the remaining molecules have lower average kinetic energy, and the temperature of the liquid decreases. This phenomenon is also called evaporative cooling and this is why evaporating sweat cools the human body. Evaporation also tends to proceed quickly with higher flow rates between the gaseous and liquid phase and in liquids with higher vapor pressure. For example, laundry on a line will dry more rapidly on a windy day than on a still day. Three key parts to evaporation are heat, atmospheric pressure, on a molecular level, there is no strict boundary between the liquid state and the vapor state. Instead, there is a Knudsen layer, where the phase is undetermined, because this layer is only a few molecules thick, at a macroscopic scale a clear phase transition interface cannot be seen. It is just that the process is slower and thus significantly less visible. If evaporation takes place in an area, the escaping molecules accumulate as a vapor above the liquid. Many of the return to the liquid, with returning molecules becoming more frequent as the density
Evaporation
–
Aerosol of microscopic water droplets suspended in the air above a hot tea cup after that water vapor has sufficiently cooled and condensed.
Water vapor is an invisible
gas, but the
clouds of condensed water droplets refract and disperse the sun light and so are visible.
Evaporation
–
Vapor pressure of water vs. temperature. 760
Torr = 1
atm.
25.
Hypoxic air fire prevention system
–
Unlike traditional fire suppression systems that usually extinguish fire after it is detected, hypoxic air is able to prevent fire. Usually 5%/10% of oxygen contained in the air is replaced by the amount of nitrogen. In a normobaric hypoxic environment, common materials cannot ignite or burn, thus, considering the fire triangle, a fire cannot occur because of the lack of sufficient oxygen. However, at 15% oxygen level, risk for fire still exists, the phenomenon of fire prevention at higher oxygen concentration than the oxygen concentration required for extinguishing an established fire has been observed and exploited for decades. Air with an oxygen content is injected to the protected volumes to lower the oxygen concentration until the desired oxygen concentration is reached. Oxygen sensors are installed in the volumes to monitor continuously the oxygen concentration. The exact oxygen level to retain in the volumes is determined after a careful and accurate assessment of materials, configurations. Tables listing ignition-limiting oxygen thresholds for some materials are available in the fire safety literature, alternatively the ignition-limiting threshold is determined by performing a proper ignition test described in BSI PAS95,2011 - Hypoxic air fire prevention systems specification. Smoke detectors are installed in protected volumes because, similar to gas suppression systems, air with low oxygen concentration is produced by hypoxic air generators, also known as air splitting units. There are three different types of hypoxic air generators, membrane-based, PSA-based and VSA-based ones, VSA-based hypoxic air generators have usually a lower energy consumption compared to PSA-based and membrane-based ones. Hypoxic air generators can be located inside or outside the protected rooms, Hypoxic air systems can be integrated with the building management system and can include systems to recover the heat generated by the hypoxic air generator that, otherwise, would be wasted. Air with low concentration is transported to the protected volumes through dedicated pipes or, more simply. In the latter case, dedicated pipes or ducts are not required, combining fire prevention, indoor climate and reduction of artefacts/food degradation is a completely new approach for a fire safety system. Unlike traditional fire-suppression systems, dedicated pipes or nozzles are not required, in situations where the installation of a traditional firefighting system would pose severe problems, fire protection can be provided with hypoxic air. The inherent simplicity of hypoxic air systems facilitates integration of building design. Fire-prevention systems which result in the content being less than 19. 5% are not permitted for occupied spaces by federal regulation in the United States. However, hypoxic air is considered by some to be safe to breathe for most people, medical studies have been undertaken on this topic. Küpper et al. say that oxygen concentration between 17. 0-14. 8% does not cause any risk for people by hypoxia
Hypoxic air fire prevention system
–
Composition of normal air vs. hypoxic air
26.
Food
–
Food is any substance consumed to provide nutritional support for an organism. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, the substance is ingested by an organism and assimilated by the organisms cells to provide energy, maintain life, or stimulate growth. Historically, humans secured food through two methods, hunting and gathering and agriculture, today, the majority of the food energy required by the ever increasing population of the world is supplied by the food industry. They address issues such as sustainability, biological diversity, climate change, nutritional economics, population growth, water supply, most food has its origin in plants. Some food is obtained directly from plants, but even animals that are used as sources are raised by feeding them food derived from plants. Cereal grain is a food that provides more food energy worldwide than any other type of crop. Corn, wheat, and rice – in all of their varieties – account for 87% of all grain production worldwide, most of the grain that is produced worldwide is fed to livestock. Some foods not from animal or plant sources include various edible fungi, fungi and ambient bacteria are used in the preparation of fermented and pickled foods like leavened bread, alcoholic drinks, cheese, pickles, kombucha, and yogurt. Another example is blue-green algae such as Spirulina, inorganic substances such as salt, baking soda and cream of tartar are used to preserve or chemically alter an ingredient. Many plants and plant parts are eaten as food and around 2,000 plant species are cultivated for food, many of these plant species have several distinct cultivars. Seeds of plants are a source of food for animals, including humans, because they contain the nutrients necessary for the plants initial growth, including many healthful fats. In fact, the majority of food consumed by human beings are seed-based foods, edible seeds include cereals, legumes, and nuts. Oilseeds are often pressed to produce rich oils - sunflower, flaxseed, rapeseed, sesame, seeds are typically high in unsaturated fats and, in moderation, are considered a health food, although not all seeds are edible. Large seeds, such as those from a lemon, pose a choking hazard, fruits are the ripened ovaries of plants, including the seeds within. Many plants and animals have coevolved such that the fruits of the former are a food source to the latter. Fruits, therefore, make up a significant part of the diets of most cultures, some botanical fruits, such as tomatoes, pumpkins, and eggplants, are eaten as vegetables. Vegetables are a type of plant matter that is commonly eaten as food. These include root vegetables, bulbs, leaf vegetables, stem vegetables, animals are used as food either directly or indirectly by the products they produce
Food
–
Various foods
Food
–
Foods from plant sources
Food
–
Various raw
meats
Food
–
Tractor and
Chaser bin
27.
Cryopreservation
–
At low enough temperatures, any enzymatic or chemical activity which might cause damage to the biological material in question is effectively stopped. Cryopreservation methods seek to reach low temperatures without causing additional damage caused by the formation of ice during freezing, traditional cryopreservation has relied on coating the material to be frozen with a class of molecules termed cryoprotectants. New methods are constantly being investigated due to the inherent toxicity of many cryoprotectants, by default it should be considered that cryopreservation alters or compromises the structure and function of cells unless it is proven otherwise for a particular cell population. Cryoconservation of animal genetic resources is the process in which genetic material is collected and stored with the intention of conservation of the breed. Mixtures of solutes can achieve similar effects, some solutes, including salts, have the disadvantage that they may be toxic at intense concentrations. In addition to the water-bear, wood frogs can tolerate the freezing of their blood, urea is accumulated in tissues in preparation for overwintering, and liver glycogen is converted in large quantities to glucose in response to internal ice formation. Both urea and glucose act as cryoprotectants to limit the amount of ice that forms, frogs can survive many freeze/thaw events during winter if not more than about 65% of the total body water freezes. Research exploring the phenomenon of Freezing frogs has been performed primarily by the Canadian researcher, snapping turtles Chelydra serpentina and wall lizards Podarcis muralis also survive nominal freezing but it has not been established to be adaptive for overwintering. In the case of Rana sylvatica one cryopreservant is ordinary glucose, one of the most important early theoreticians of cryopreservation was James Lovelock known for Gaia theory. He suggested that damage to red blood cells during freezing was due to osmotic stress, during the early 1950s, Lovelock had also suggested that increasing salt concentrations in a cell as it dehydrates to lose water to the external ice might cause damage to the cell. Cryopreservation of tissue during recent times began with the freezing of fowl sperm, the process was applied to humans during the 1950s with pregnancies obtained after insemination of frozen sperm. Increased understanding of the mechanism of freezing injury to cells emphasised the importance of controlled or slow cooling to obtain maximum survival on thawing of the living cells, the ability of cryoprotectants, in the early cases glycerol, to protect cells from freezing injury was discovered accidentally. Freezing injury has two aspects, direct damage from the ice crystals and secondary damage caused by the increase in concentration of solutes as progressively more ice is formed. Storage at very cold temperatures is presumed to provide an indefinite longevity to cells, researchers experimenting with dried seeds found that there was noticeable variability of deterioration when samples were kept at different temperatures – even ultra-cold temperatures. Many of these effects can be reduced by cryoprotectants, once the preserved material has become frozen, it is relatively safe from further damage. However, estimates based on the accumulation of radiation-induced DNA damage during cryonic storage have suggested a maximum period of 1000 years. Solution effects As ice crystals grow in freezing water, solutes are excluded, high concentrations of some solutes can be very damaging. Extracellular ice formation When tissues are cooled slowly, water migrates out of cells, too much extracellular ice can cause mechanical damage to the cell membrane due to crushing
Cryopreservation
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Cryopreservation of plant shoots. Open tank of liquid nitrogen behind.
Cryopreservation
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A tank of
liquid nitrogen, used to supply a cryonic freezer (for storing laboratory samples at a temperature of about −150 °C)
Cryopreservation
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Four different
ecotypes of
Physcomitrella patens stored at the
IMSC.
28.
Blood
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Blood is a body fluid in humans and other animals that delivers necessary substances such as nutrients and oxygen to the cells and transports metabolic waste products away from those same cells. In vertebrates, it is composed of blood cells suspended in blood plasma, plasma, which constitutes 55% of blood fluid, is mostly water, and contains dissipated proteins, glucose, mineral ions, hormones, carbon dioxide, and blood cells themselves. Albumin is the protein in plasma, and it functions to regulate the colloidal osmotic pressure of blood. The blood cells are red blood cells, white blood cells. The most abundant cells in blood are red blood cells. These contain hemoglobin, a protein, which facilitates oxygen transport by reversibly binding to this respiratory gas. In contrast, carbon dioxide is mostly transported extracellularly as bicarbonate ion transported in plasma, vertebrate blood is bright red when its hemoglobin is oxygenated and dark red when it is deoxygenated. Some animals, such as crustaceans and mollusks, use hemocyanin to carry oxygen, insects and some mollusks use a fluid called hemolymph instead of blood, the difference being that hemolymph is not contained in a closed circulatory system. In most insects, this blood does not contain oxygen-carrying molecules such as hemoglobin because their bodies are small enough for their system to suffice for supplying oxygen. Jawed vertebrates have an immune system, based largely on white blood cells. White blood cells help to resist infections and parasites, platelets are important in the clotting of blood. Arthropods, using hemolymph, have hemocytes as part of their immune system, Blood is circulated around the body through blood vessels by the pumping action of the heart. Medical terms related to blood often begin with hemo- or hemato- from the Greek word αἷμα for blood. In terms of anatomy and histology, blood is considered a form of connective tissue, given its origin in the bones. The average adult has a volume of roughly 5 litres. These blood cells consist of erythrocytes, leukocytes, and thrombocytes, by volume, the red blood cells constitute about 45% of whole blood, the plasma about 54. 3%, and white cells about 0. 7%. Whole blood exhibits non-Newtonian fluid dynamics, if all human hemoglobin were free in the plasma rather than being contained in RBCs, the circulatory fluid would be too viscous for the cardiovascular system to function effectively. One microliter of blood contains,4.7 to 6.1 million,4.2 to 5.4 million erythrocytes, Red blood cells contain the bloods hemoglobin, mature red blood cells lack a nucleus and organelles in mammals
Blood
–
Human
blood smear: a –
erythrocytes; b –
neutrophil; c –
eosinophil; d –
lymphocyte.
Blood
–
A
scanning electron microscope (SEM) image of a normal
red blood cell, a
platelet, and a
white blood cell.
Blood
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Two tubes of
EDTA -anticoagulated blood. Left tube: after standing, the RBCs have settled at the bottom of the tube. Right tube: contains freshly drawn blood.
Blood
–
Vertebrate red blood cell types, measurements in micrometers
29.
Sperm
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Sperm is the male reproductive cell and is derived from the Greek word sperma. In the types of reproduction known as anisogamy and its subtype oogamy. A uniflagellar sperm cell that is motile is referred to as a spermatozoon, Sperm cells cannot divide and have a limited life span, but after fusion with egg cells during fertilization, a new organism begins developing, starting as a totipotent zygote. The human sperm cell is haploid, so that its 23 chromosomes can join the 23 chromosomes of the egg to form a diploid cell. In mammals, sperm develops in the testicles and is released from the penis, the mammalian sperm cell consists of a head, neck, a midpiece and a tail. The head contains the nucleus with densely coiled chromatin fibres, surrounded anteriorly by an acrosome, the neck contains the sperm centriole. The midpiece has a central core with many mitochondria spiralled around it, used for ATP production for the journey through the female cervix, uterus. The tail or flagellum executes the lashing movements that propel the spermatocyte, although semen contains millions of sperm, the egg will admit only one. The other ones will die and be absorbed. The spermatozoa of animals are produced through spermatogenesis inside the gonads via meiotic division. The initial spermatozoon process takes around 70 days to complete, the spermatid stage is where the sperm develops the familiar tail. The next stage where it becomes fully mature takes around 60 days when it is called a spermatozoan, Sperm cells are carried out of the male body in a fluid known as semen. Human sperm cells can survive within the reproductive tract for more than 5 days post coitus. Semen is produced in the vesicles, prostate gland and urethral glands. In 2016 scientists at Nanjing Medical University claimed they had produced cells resembling mouse spermatids artificially from stem cells and they injected these spermatids into mouse eggs and produced pups. Sperm quantity and quality are the parameters in semen quality. Thus, in humans, it is a measure of fertility in a man, the genetic quality of sperm, as well as its volume and motility, all typically decrease with age. Human sperm cells are vulnerable to free radical attack and the generation of oxidative DNA damage
Sperm
–
Sperm and egg fusing
Sperm
–
Diagram of a human sperm cell
Sperm
–
Human sperm stained for semen quality testing.
30.
Ovum
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The egg cell, or ovum, is the female reproductive cell in oogamous organisms. The egg cell is not capable of active movement. When egg and sperm fuse, a cell is formed. Karl Ernst von Baer discovered the mammalian ovum in 1827, the fusion of spermatozoa with ova was observed by Oskar Hertwig in 1876. In animals, egg cells are known as ova. The term ovule is used for the young ovum of an animal, in vertebrates, ova are produced by female gonads called ovaries a number of ova are present at birth in mammals and mature via oogenesis. White et al. disproved the longstanding dogma that all of the ova are produced before birth, the team from the Vincent Center for Reproductive Biology, Massachusetts, Boston could prove that oocyte fromation takes place in ovaries of reproductive-age women. This report challenged a fundamental belief, held since the 1950s, in all mammals the ovum is fertilized inside the female body. The human ova grow from primitive germ cells that are embedded in the substance of the ovaries, each of them divides repeatedly to give secretions of the uterine glands, ultimately forming a blastocyst. The ovum is one of the largest cells in the human body, the human ovum measures approximately 0.12 mm in diameter. Ooplasm is the yolk of the ovum, a substance at its center, which contains its nucleus, named the germinal vesicle. Mammalian ova contain only an amount of the nutritive yolk. In contrast, bird eggs contain enough to supply the chick with nutriment throughout the period of incubation. In the oviparous animals the ova develop protective layers and pass through the oviduct to the outside of the body and they are fertilized by male sperm either inside the female body, or outside. After fertilization, an embryo develops, nourished by nutrients contained in the egg and it then hatches from the egg, outside the mothers body. See egg for a discussion of eggs of oviparous animals, the egg cells cytoplasm and mitochondria are the sole means the egg is able to reproduce by mitosis and eventually form a blastocyst after fertilization. Some fish, reptiles and many use this technique. Nearly all land plants have alternating diploid and haploid generations, gametes are produced by the gametophyte, which is the haploid generation
Ovum
–
Ovum and sperm fusing together
Ovum
–
A human ovum with
corona radiata surrounding it
Ovum
