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tropism

(Encyclopedia)tropism trōpˈĭzəm [key], involuntary response of an organism, or part of an organism, involving orientation toward (positive tropism) or away from (negative tropism) one or more external stimuli. ...

humidity

(Encyclopedia)humidity, moisture content of the atmosphere, a primary element of climate. Humidity measurements include absolute humidity, the mass of water vapor per unit volume of natural air; relative humidity (...

metamorphism

(Encyclopedia)metamorphism, in geology, process of change in the structure, texture, or composition of rocks caused by agents of heat, deforming pressure, shearing stress, hot, chemically active fluids, or a combin...

aluminum

(Encyclopedia)aluminum ălˌyo͞omĭnˈēəm [key], metallic chemical element; symbol Al; at. no. 13; at. wt. 26.98154; m.p. 660.37℃; b.p. 2,467℃; sp. gr. 2.6989 at 20℃; valence +3. Aluminum is a silver-white...

chemical equation

(Encyclopedia)chemical equation, group of symbols representing a chemical reaction. There are a number of other symbols used in chemical equations. A symbol written above or below the reaction arrow indicates spe...

Nernst, Walther Hermann

(Encyclopedia)Nernst, Walther Hermann välˈtər hĕrˈmän nĕrnst [key], 1864–1941, German physicist and chemist, a founder of modern physical chemistry. After doing outstanding research on osmotic pressure and...

microwave oven

(Encyclopedia)microwave oven, device that uses microwaves to rapidly cook food. The microwaves cause water molecules in the food to vibrate, producing heat, which is distributed through the food by induction. A spe...

molasses

(Encyclopedia)molasses, sugar byproduct, the brownish liquid residue left after heat crystallization of sucrose (commercial sugar) in the process of refining. Molasses contains chiefly the uncrystallizable sugars a...

actinometer

(Encyclopedia)actinometer ăkˌtənŏmˈətər [key], instrument used to measure the heating power of radiation. Actinometers are used chiefly in meteorology to measure solar radiation as transmitted directly by th...

touch

(Encyclopedia)touch, tactile sensation received by the skin, enabling the organism to detect objects or substances in contact with the body. End organs (nerve endings) in the skin convey the impression to the brain...