paraffins |
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Paraffins are obsolescent term for alkanes. Still widely used in the petrochemical industry. |
paramagnetism |
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Paramagnetism is a type of magnetism characterized by a positive magnetic susceptibility, so that the material becomes weakly magnetized in the direction of an external field. The magnetization disappears when the field in removed. |
pascal |
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Paramagnetism is a type of magnetism characterized by a positive magnetic susceptibility, so that the material becomes weakly magnetized in the direction of an external field. The magnetization disappears when the field in removed. |
Paschen series |
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Paschen series are the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the state with principal quantum number n = 3 and successive higher states. |
Pauli exclusion principle |
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Pauli exclusion principle is the statement that two electrons in an atom cannot have identical all four quantum numbers. It was first formulated in 1925 by Austrian-born Swiss physicst Wolfgang Ernst Pauli (1900-1958). |
Peltier effect |
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Peltier effect is the absorption or generation of heat (depending on the current direction) which occurs when an electric current is passed through a junction between two materials. |
peptides |
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Peptides are amides derived from two or more amino acids (the same or different) linked by peptide bonds. These bonds are formed by the reaction between adjancent carboxyl (-COOH) i amino (-NH2) groups with the elimination of water. |
periodic table |
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Periodic table is a table of the elements, written in sequence in the order of atomic number or atomic weight and arranged in horizontal rows (periods) and vertical columns (groups) to illustrate the occurrence of similarities in the properties of the elements as a periodic function of the sequence. The original form was proposed by Dmitri Mendeleev (1834-1907) in 1869 using relative atomic masses. |
periods |
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Periods are horizontal rows in the periodic table. Each period beginning with an alkali metal (one electron in the outermost principal quantum level) and ending with an noble gas (each having eight electrons in the outermost principal quantum level, except for helium, which is limited to two). |
peroxides |
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Peroxides are compounds of structure ROOR in which R may be any organic group. In inorganic chemistry, salts of the anion O2-2. They are strong oxidizing agents. |
petroleum ether |
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Petroleum ether is the petroleum fraction consisting of C5 and C6 hydrocarbons and boiling in the range 35 °C to 60 °C; commonly used as a laboratory solvent. |
pH |
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pH is a convenient measure of the acid-base character of a solution, usually defined by
pH = -logc(H+)
where c(H+) is the concentration of hydrogen ions in moles per liter. The more precise definition is in terms af activity rather than concentration.
A solution of pH 0 to 7 is acid, pH of 7 is neutral, pH over 7 to 14 is alkaline. |
phase |
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Phase is a portion of a physical system (solid, liquid, gas) that is homogeneous throughout, has definable boundaries, and can be separated physically from other phases. |
phase diagram |
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Phase diagram is a graphical representation of the equilibrium relationships between phases (such as vapor-liquid, liquid-solid) of a chemical compound, mixture of compounds, or solution. |
phenols |
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Phenols are compounds having one or more hydroxy groups attached to benzene or other arene ring. |
photoelectric effect |
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Photoelectric effect is the complete absorption of a photon by a solid with the emission of an electron. The energy of a photon (hν) is
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photon |
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Photon is an elementary particle of zero mass and spin 1/2. The photon is involved in electromagnetic interactions and is the quantum of electromagnetic radiation. The photon may also be regarded as a unit of energy equal to
E = h∙ν
where h is Planck constant and ν is the frequency of the radiation. |
pK |
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pK is the negative logarithm (base 10) of an equilibrium constant K. |
Planck constant |
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Planck constant (h) is a constant that when multipled by the frequency of radiation gives the quantity of energy contained in one quantum.
E = hν
Equal to 6.6260755(40)∙10-34 J s. It is named after Max Planck (1858-1947). |
plasma |
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Plasma is a highly ionized gas in which the charge of the electrons is balanced by the charge of the positive ions, so that the system as a whole is electrically neutral. Temperatures of 10 000 °C to 15 000 °C can be reached. |
polymer |
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Polymer is a substance composed of molecules of high relative molecular mass (molecular weight), the structure of which essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass (monomers). In most cases the number of monomers is quite large and often is not precisely known. A single molecule of a polymer is called a macromolecule. |
polypeptides |
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Polypeptides are peptides containing ten or more amino acid residues. The properties of a polypeptide are determined by the type and sequence of its constituent amino acids. |
polysaccharides |
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Polysaccharides are compounds consisting of a large number of monosaccharides linked together by glycosidic bonds. Some important examples are starch, glycogen, and cellulose. |
positron |
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Positron is the antiparticle of the electron. It has the same mass and spin as an electron, and an equal but opposite charge. |
pressure |
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Pressure (p) is the force acting normally on unit area of a surface. It is measured in pascals in Si units (Pa)
p = F/A |
proton |
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Proton is a stable elementary particle of unit positive charge and spin 1/2. Protons and neutrons, which are collectively called nucleons, are the constituents of the nucleus. |
qualitative analysis |
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Qualitative analysis involves determining the nature of a pure unknown compound or the compounds present in a mixture. |
quantitative analysis |
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Quantitative analysis is the determination of the amount of substances present in a sample. |
quantum |
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Quantum is the smallest quantity of energy that can be emitted (or absorbed) in the form of electromagnetic radiation. Energy of a quantum (E) is equal to
E = h∙ν
where h is Planck constant and ν is the frequency of the radiation. |
quasicrystal |
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Quasicrystal is a solid having conventional crystalline properties but whose lattice does not display translational periodicity. |
