In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, a polyatomic ion with the formula of CO2−3. The name may refer to a carbonate ester, an organic compound containing the carbonate group C2; the term is used as a verb, to describe carbonation: the process of raising the concentrations of carbonate and bicarbonate ions in water to produce carbonated water and other carbonated beverages – either by the addition of carbon dioxide gas under pressure, or by dissolving carbonate or bicarbonate salts into the water. In geology and mineralogy, the term "carbonate" can refer both to carbonate minerals and carbonate rock, both are dominated by the carbonate ion, CO2−3. Carbonate minerals are varied and ubiquitous in chemically precipitated sedimentary rock; the most common are CaCO3, the chief constituent of limestone. Sodium carbonate and potassium carbonate have been used since antiquity for cleaning and preservation, as well as for the manufacture of glass.
Carbonates are used in industry, e.g. in iron smelting, as a raw material for Portland cement and lime manufacture, in the composition of ceramic glazes, more. The carbonate ion is the simplest oxocarbon anion, it consists of one carbon atom surrounded by three oxygen atoms, in a trigonal planar arrangement, with D3h molecular symmetry. It has a molecular mass of 60.01 g/mol and carries a total formal charge of −2. It is the conjugate base of the hydrogen carbonate ion, HCO−3, the conjugate base of H2CO3, carbonic acid; the Lewis structure of the carbonate ion has two single bonds to negative oxygen atoms, one short double bond to a neutral oxygen. This structure is incompatible with the observed symmetry of the ion, which implies that the three bonds are long and that the three oxygen atoms are equivalent; as in the case of the isoelectronic nitrate ion, the symmetry can be achieved by a resonance among three structures: This resonance can be summarized by a model with fractional bonds and delocalized charges: Metal carbonates decompose on heating, liberating carbon dioxide from the long term carbon cycle to the short term carbon cycle and leaving behind an oxide of the metal.
This process is called calcination, after calx, the Latin name of quicklime or calcium oxide, CaO, obtained by roasting limestone in a lime kiln. A carbonate salt forms when a positively charged ion, M+, M2+, or M3+, associates with the negatively charged oxygen atoms of the ion by forming electrostatic attractions with them, forming an ionic compound: 2 M+ + CO2−3 → M2CO3M2+ + CO2−3 → MCO32 M3+ + 3 CO2−3 → M23Most carbonate salts are insoluble in water at standard temperature and pressure, with solubility constants of less than 1 × 10−8. Exceptions include lithium, sodium and ammonium carbonates, as well as many uranium carbonates. In aqueous solution, bicarbonate, carbon dioxide, carbonic acid exist together in a dynamic equilibrium. In basic conditions, the carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent. In more acid conditions, aqueous carbon dioxide, CO2, is the main form, with water, H2O, is in equilibrium with carbonic acid – the equilibrium lies towards carbon dioxide.
Thus sodium carbonate is basic, sodium bicarbonate is weakly basic, while carbon dioxide itself is a weak acid. Carbonated water is formed by dissolving CO2 in water under pressure; when the partial pressure of CO2 is reduced, for example when a can of soda is opened, the equilibrium for each of the forms of carbonate shifts until the concentration of CO2 in the solution is equal to the solubility of CO2 at that temperature and pressure. In living systems an enzyme, carbonic anhydrase, speeds the interconversion of CO2 and carbonic acid. Although the carbonate salts of most metals are insoluble in water, the same is not true of the bicarbonate salts. In solution this equilibrium between carbonate, carbon dioxide and carbonic acid changes to the changing temperature and pressure conditions. In the case of metal ions with insoluble carbonates, e.g. CaCO3, formation of insoluble compounds results; this is an explanation for the buildup of scale inside pipes caused by hard water. Systematic additive IUPAC name for carbonate anion is trioxidocarbonate.
Cyanide anion CN− is named nitridocarbonate. Following this logic, e.g. carbonate in the systematic additive nomenclature would mean carbide anion, but it is not the case. In organic chemistry a carbonate can refer to a functional group within a larger molecule that contains a carbon atom bound to three oxygen atoms, one of, double bonded; these compounds are known as organocarbonates or carbonate esters, have the general formula ROCOOR′, or RR′CO3. Important organocarbonates include dimethyl carbonate, the cyclic compounds ethylene carbonate and propylene carbonate, the phosgene replacement, triphosgene, it works as a buffer in the blood as follows: when pH is low, the concentration of hydrogen ions is too high, so one exhales CO2. This will cause the equation to shift left decreasing the concentration of H+ ions, causing a more basic pH; when pH is too high, the concentration of hydrogen ions in the blood is too low, so the kidneys excrete bicarbonate. This causes the equation to shift right increasing the concentration of hy
A countertop is a horizontal work surface in kitchens or other food preparation areas, bathrooms or lavatories, workrooms in general. It is installed upon and supported by cabinets; the surface is positioned at an ergonomic height for the user and the particular task for which it is designed. A countertop may be constructed of various materials with different attributes of functionality and aesthetics; the countertop may have built-in appliances, or accessory items relative to the intended application. In Australian English and British English, the term counter is reserved for a surface of this type that forms a boundary between a space for public use and a space for workers to carry out service tasks. In other contexts, the term bench or benchtop is used; the common fitted Western-style kitchen, developed in the early 20th century, is an arrangement of assembled unit cabinetry covered with a more-or-less continuous countertop work surface. The "unfitted" kitchen design style exemplified by Johnny Grey may include detached and/or varied countertop surfaces mounted on discrete base support structures.
Primary considerations of material choice and conformation are durability, hygienics and cost. When installed in a kitchen on standard wall-mounted base unit cabinets, countertops are about 25-26 inches from front to back and are designed with a slight overhang on the front edge; this allows for a convenient reach to objects at the back of the countertop while protecting the base cabinet faces. In the UK the standard width is 600 mm. Finished heights from the floor will vary depending on usage but will be 35-36", with a material thickness depending on that chosen, they may include an integrated or applied backsplash to prevent spills and objects from falling behind the cabinets. Kitchen countertops may be installed on freestanding islands, dining areas or bars and table tops, other specialized task areas; the horizontal surface and vertical edges of the countertop can be decorated in manners ranging from plain to elaborate. They are conformed to accommodate the installation of sinks, stoves and cooktops, or other accessories such as dispensers, integrated drain boards, cutting boards.
Laboratory countertops are countertops used in science fields for educational labs or research purposes. They can be used to place equipments, tools and chemicals. Characteristics of laboratory countertops are determined according to what reagents or corrosive chemicals are being used; the purpose of the countertop would be different depending on whether it is used in a chemistry lab, physics lab, food science lab, microbiology or a biology lab. Common characteristics of preferred laboratory countertops are ones that are strong and water-, moisture- or chemical resistant. Depending on the objectives of a lab, they may additionally be required to be resistant to acids or high temperatures. Many laboratory countertops are equipped with drawers that can be used to store materials that might get in the way while conducting an experiment. Materials such as lab notebooks, extra papers and folders are advised and expected to be stored away in the provided spaces or inside the drawer; the laboratory countertops' styles and variations may differ according to where they are and what labs they are being used for.
They are often made of different materials depending on their usage. The most common and durable type of material used is phenolic resin because they are lightweight, strong and moisture resistant, it can handle heat exposure up beyond this temperature Epoxy Resin is used. Phenolic Resin and Epoxy Resin are both functionally equivalent, but differ in their heat handling abilities. Other materials to build laboratory countertops may include plastic laminate, stainless steel and wood. Countertops can be made from a wide range of materials and the cost of the completed countertop can vary depending on the material chosen; the durability and ease of use of the material rises with the increasing cost of the material but some costly materials are neither durable nor user-friendly. Some common countertop materials are as follows: Natural stones Granite Limestone Marble Soapstone Gabbro Slate Silicate mineral Travertine Quartz Wood Hardwood Softwood Metals Stainless steel Copper Zinc Aluminium Crafted glass Manufactured materials Concrete Cast-in-place Precast Processed slabs Compressed paper or fiber Cultured marble High-pressure laminates Post-formed high-pressure decorative laminates Self-edged high-pressure decorative laminates Quartz surfacing or engineered stone is 99.9% solid @ 93% aggregate / 7% polyester resin and binders Recycled Glass surface either with concrete or polyester resin binders Solid-surface acrylic plastic materials Solid-surface polyester acrylic Terrazzo Tile Cast-in-place materials Natural stone suspended in a resin Post-consumer glass suspended in a resin Epoxy Phenolic resin Natural stone is one of the most used materials in countertops.
Natural stone or dimension stone slabs are shaped using cutting and finishing equipment in the shop of the fabricator. The edges are put on by hand-held routers, grinders, or CNC equipment. If the stone has a variegated pattern, the stone may be laid out in final position in the shop for the customer's inspection, or
Charles Spearman developed his two-factor theory of intelligence using factor analysis. His research not only led him to develop the concept of the g factor of general intelligence, but the s factor of specific intellectual abilities. L. L. Thurstone, Howard Gardner, Robert Sternberg researched the structure of intelligence, in analyzing their data, concluded that a single underlying factor was influencing the general intelligence of individuals. However, Spearman was criticized in 1916 by Godfrey Thomson, who claimed that the evidence was not as crucial as it seemed. Modern research is still expanding this theory by investigating Spearman's law of diminishing returns, adding connected concepts to the research. In 1904, Charles Spearman had developed a statistical procedure called factor analysis. In factor analysis, related variables are tested for correlation to each other the correlation of the related items are evaluated to find clusters or groups of the variables. Spearman tested; such tasks include: distinguishing pitch, perceiving weight and colors and mathematics.
When analyzing the data he collected, Spearman noted that those that did well in one area scored higher in other areas. With this data, Spearman concluded that there must be one central factor that influences our cognitive abilities. Spearman termed this general intelligence g. Due to the controversy of the structure of intelligence, other psychologists published their relevant research. Other than Charles Spearman, three others developed a hypothesis regarding the structure of intelligence. L. L. Thurstone tested subjects on 56 different abilities, he categorized them as: spatial ability, numerical ability, word fluency, perceptual speed, verbal comprehension, inductive reasoning. Other researchers, interested in this new research study, analyzed Thurstone's data, discovering that those scored high in one category did well in the others; this finding gives support that there is an underlying factor influencing them, namely g. Howard Gardner suggested in his theory of multiple intelligences that intelligence is formed out of multiple abilities.
He recognized eight intelligences: linguistic, spatial, interpersonal, logical-mathematical, bodily-kinesthetic, naturalist. He considered the possibility of a ninth intelligent ability, existential intelligence. Gardner proposed. Instead, his results showed that each of his eight intelligences correlate positively with each other. After further analysis, Gardner found that logic, spatial abilities and mathematics are all linked in some way, giving support for an underlying g factor, prominent in all intelligence in general. Robert Sternberg agreed with Gardner that there were multiple intelligences, but he narrowed his scope to just three in his triarchic theory of intelligence: analytical and practical, he classified analytical intelligence as problem-solving skills in academics. Creative intelligence is considered how people react adaptively in new situations, or create novel ideas. Practical intelligence is defined as the everyday logic used when multiple solutions or decisions are possible.
When Sternberg analyzed his data the relationship between the three intelligences surprised him. The data resembled. All three mental abilities correlated with one another, evidence that one basic factor, g, was the primary influence. Not all psychologists agreed with his general intelligence. In 1916, Godfrey Thomson wrote a paper criticizing Spearman's g:The object of this paper is to show that the cases brought forward by Professor Spearman in favor of the existence of General Ability are by no means "crucial." They are it is true not inconsistent with the existence of such a common element but neither are they inconsistent with its non-existence. The essential point about Professor Spearman's hypothesis is the existence of this General Factor. Both he and his opponents are agreed that there are Specific Factors peculiar to individual tests, both he and his opponents agree that there are Group Factors which run through some but not all tests; the difference between them is that Professor Spearman says there is a further single factor which runs through all tests, that by pooling a few tests the Group Factors can soon be eliminated and a point reached where all the correlations are due to the General Factor alone.
Spearman came up with the term General Intelligence, or as he called it, g, to measure intelligence in his Two Theory on Intelligence. Spearman first researched in an experiment with 24 children from a small village school measuring three intellectual measures, based on teachers rankings, to address intellectual and sensory as the two different sets of measure: School Cleverness, Common Sense A and Common Sense B, his results showed the average r between intellectual and sensory measures to be +.38, School Cleverness and Commonsense to be at +0.55, the three tasks intercorrelated at +0.25. This data was looked at other populations including high school. Spearman proposed that intellectual and sensory measure be combined as assessment of general intelligence. Spearman proposed; the general intelligence, g, influences the performance on all mental tasks, while another component influences abilities on a particular task. To explain the differences in performance on different tasks, Spearman hypothesized that this other component was specific to a certain aspect of intelligence.