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Willard Gibbs, Graphical Methods in the Thermodynamics of Fluids The concept of entropy is described by two principal approaches, the macroscopic perspective of classical thermodynamics, and the microscopic description central to statistical mechanics. The classical approach defines entropy in terms of macroscopically measurable physical properties, such as bulk mass, volume, pressure, and ...
t. e. In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which an atomic nucleus emits a beta particle (fast energetic electron or positron ), transforming into an isobar of that nuclide. For example, beta decay of a neutron transforms it into a proton by the emission of an electron accompanied by an antineutrino; or ...
Schrödinger's cat: a cat, a flask of poison, and a radioactive source connected to a Geiger counter are placed in a sealed box. As illustrated, the quantum description uses a superposition of an alive cat and one that has died. In quantum mechanics, Schrödinger's cat is a thought experiment, sometimes described as a paradox, of quantum ...
Gamma decay: this process results from a change in the energy level of the nucleus to a lower state, resulting in the emission of electromagnetic radiation. The excited state of a nucleus which results in gamma emission usually occurs following the emission of an alpha or a beta particle. Thus, gamma decay usually follows alpha or beta decay.
Electron capture ( K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shells. This process thereby changes a nuclear proton to a neutron and simultaneously causes the emission of an ...
In quantum field theory, a false vacuum [1] is a hypothetical vacuum that is relatively stable, but not in the most stable state possible. [2] In this condition it is called metastable. It may last for a very long time in this state, but could eventually decay to the more stable one, an event known as false vacuum decay.
This was the original definition of Sørensen in 1909, which was superseded in favor of pH in 1924. [H] is the concentration of hydrogen ions, denoted [H +] in modern chemistry. More correctly, the thermodynamic activity of H + in dilute solution should be replaced by [H +]/c 0, where the standard state concentration c 0 = 1 mol/L. This ratio ...
In chemical kinetics, a reaction rate constant or reaction rate coefficient ( ) is a proportionality constant which quantifies the rate and direction of a chemical reaction by relating it with the concentration of reactants. [1] For a reaction between reactants A and B to form a product C, a A + b B → c C. where.