1. Atmosphere is the column of air which is extending several hundred kilometers above the surface the Earth's surface. The density of this air decreases as you proceed up from the surface. The air in the atmosphere consists of 78 % nitrogen, 21 % oxygen, and 0.9 % argon. The remaining 0.1 % of the atmosphere consists of ozone, water vapor, carbon dioxide, methane, helium, and neon. The atmosphere is divided into different regions. The lowest two layers are the troposphere (the layer closest to the earth) and the stratosphere respectively. These two layers contain more than 99 % of the atmospheric molecules.
2. Standard atmosphere (atm) is an obsolete pressure and stress unit which should be discontinued. It is unit of pressure equal to the air pressure measured at mean sea level.
1 atm = 101 325 Pa
Technical atmosphere (at) is an obsolete MKpS pressure and sttress derived unit.
1 at = 98 066.5 Pa
1 atm = 1.033 227 453 at
Becquerel (Bq) is the SI derived unit, with a special name, for radioactivity, equal to s-1. It describes a radioactivity of an amount of radionuclide decaying at the rate, on average, of one spontaneous nuclear transition per second. The unit was named after the French scientist Antoine Henri Becquerel (1852-1908) (disintegrations per unit time), equal to s-1.
Atom is an atom is the smallest particle of an element that retains the chemical properties of the element. Rutherford-Bohr’s model represents the atom as a positively charged core of a size around 10-14 m composed of protons (positive particles) and neutrons (neutral particles) around which negatively charged electrons circle. The number of protons and electrons are equal, so the atom is an electrically a neutral particle. Diameter of the atom is about 10-10 m.
Boiling point is the temperature at which the vapour pressure of a liquid is equal to the external pressure on the liquid. The standard boiling point is the temperature at which the vapour pressure of a liquid equals standard pressure (101 325 Pa).
Blackbody radiation is the radiation emitted by a perfect blackbody, i.e., a body which absorbs all radiation incident on it and reflects none. The primary law governing blackbody radiation is the Planck Radiation Law, which governs the intensity of radiation emitted by unit surface area into a fixed direction (solid angle) from the blackbody as a function of wavelength for a fixed temperature. The Planck Law can be expressed through the following equation
where λ is the wavelength, h is Planck’s constant, c is the speed of light, k is the Boltzmann constant, and T is the temperature.
The Boltzmann constant (k or kB) is the physical constant describing the relationship between the thermodynamic temperature and the average kinetic energy of particles in a gas. It equals the molar gas constant R divided by the Avogadro constant NA and has the value 1.380 648 52(79)×10-23 J/K. It is named after the Austrian physicist Ludwig Eduard Boltzmann (1844-1906).
Burette is a graded glass pipe which on its lower side has a glass faucet by which it can drop a precise quantity of liquid. Inner diameter of a burette must be equal in its whole length, because the accuracy of volume measurement depends upon that. Burettes are primarily used in volumetric analysis for titration with standard solution reagent. Most often Schellbach’s burette is used, graded on 50 mL with division of scale on 0.1 mL. Every burette is calibrated on discharge. For serial determining automatic burettes are used.
Chemical reaction is a change of chemical properties of substances which react with each other. By means of a chemical reaction new substances are created by bond breaking between atoms and molecules of reactants and their reuniting in a new way, thereby creating products. Chemical reactions can be shown by chemical equations.
Chemical symbols are a derived way of showing elements in a formula or equation. Each symbol represents one atom and it usually consists of the first two letters of the Greek or Latin name of the element.
Generalic, Eni. "Equal-arm balance." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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