Decibel

a unit for measuring the level of sound which has the symbol dB.

Taken from Dictionary of Science

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The decibel (dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity) relative to a specified or implied reference level. Since it expresses a ratio of two quantities with the same unit, it is a dimensionless unit. A decibel is one tenth of a bel, a seldom-used unit.

The decibel is widely known as a measure of sound pressure level, but is also used for a wide variety of other measurements in science and engineering (particularly acoustics, electronics, and control theory) and other disciplines. It confers a number of advantages, such as the ability to conveniently represent very large or small numbers, a logarithmic scaling that roughly corresponds to the human perception of sound and light, and the ability to carry out multiplication of ratios by simple addition and subtraction.

The decibel symbol is often qualified with a suffix, which indicates which reference quantity or frequency weighting function has been used. For example, "dBm" indicates that the reference quantity is one milliwatt, while "dBu" is referenced to 0.775 volts RMS.

The definitions of the decibel and bel use base-10 logarithms. For a similar unit using natural logarithms to base e, see neper.

Taken from Wikipedia

Watt

(W) a unit of power that is the rate of WORK done at I JOULE per second, i.e. I W = 1 Js^-1.

Taken from Dictionary of Science

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The watt is a derived unit of power in the International System of Units (SI), named after the 18th-century Scottish engineeer James Watt. Its unit symbol is W. The unit measures the rate of energy conversion.

• One watt is equal to 1 joule (J) of energy per second.

• In terms of mechanical energy, one watt is the rate at which work is done when an object is moved at a speed of one meter per second against a force of one newton.

1W = 1Js^-1 = 1kgm²s^-3 = 1Nms^-1

• By the definitions of electric potential (volt) and current (ampere), work is done at a rate of one watt when one ampere flows through a potential difference of one volt.

1W=1V×1A

Taken from Wikipedia

Valency

is the bonding potential or combining power of an atom or group, measured by the number of hydrogen ions (H⁺, or equivalent) that the atoms could combine with or replace. In an ionic compound, the charge on each ion represents the valency, e.g., in NaCl, both Na⁺ and Cl^- have a valency of one. In covalent compounds, the valency is represented by the number of bonds formed. In carbon dioxide, CO₂, carbon has a valency of 4 and oxygen 2.

The electronic theory of valency explains bonds through the assumption that specific arrangements of outer electrons in atoms (outer shells of eight electrons) give stability (as with the inert gases, which have such a structure) through the transfer or sharing of electrons. Thus with the combination of sodium with chlorine, sodium has one electron in the outer shell, which it loses to chlorine to form the stable structure of the inert gas neon. Similarly, the gain of one electron by chlorine gives it the stable structure of argon.

Taken from Dictionary of Science

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In chemistry, valence, also known as valency or valency number, is a measure of the number of chemical bonds formed by the atoms of a given element. Over the last century, the concept of valence evolved into a range of approaches for describing the chemical bond, including Lewis structures (1916), valence bond theory (1927), molecular orbitals (1928), valence shell electron pair repulsion theory (1958) and all the advanced methods of quantum chemistry.

Taken from Wikipedia

Saccharin

a white, crystalline powder with about 500 times the sweetening power of sucrose. It is not very soluble in water but is used extensively as a sweetening agent, in the form of the sodium salt.

Taken from Dictionary of Science

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Saccharin is an artificial sweetener. The basic substance, benzoic sulfimide, has effectively no food energy and is much sweeter than sucrose, but has an unpleasant bitter or metallic aftertaste, especially at high concentrations. In countries where saccharin is allowed as a food additive, it is used to sweeten products such as drinks, candies, medicines, and toothpaste.

Taken from Wikipedia