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  2. Glossary of physics - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_physics

    Is zero-referenced against a perfect vacuum, using an absolute scale, so it is equal to gauge pressure plus atmospheric pressure. absolute scale Any system of measurement that begins at a minimum, or zero point, and progresses in only one direction. The zero point of an absolute scale is a natural minimum, leaving only one direction in which to ...

  3. Oxygen - Wikipedia

    en.wikipedia.org/wiki/Oxygen

    In aquatic animals, dissolved oxygen in water is absorbed by specialized respiratory organs called gills, through the skin or via the gut; in terrestrial animals such as tetrapods, oxygen in air is actively taken into the body via specialized organs known as lungs, where gas exchange takes place to diffuse oxygen into the blood and carbon ...

  4. Glossary of chemistry terms - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_chemistry_terms

    Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...

  5. Matter - Wikipedia

    en.wikipedia.org/wiki/Matter

    Fully 70% of the matter density in the universe appears to be in the form of dark energy. Twenty-six percent is dark matter. Only 4% is ordinary matter. So less than 1 part in 20 is made out of matter we have observed experimentally or described in the standard model of particle physics. Of the other 96%, apart from the properties just ...

  6. Breathing gas - Wikipedia

    en.wikipedia.org/wiki/Breathing_gas

    A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas. Other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed habitats such as scuba equipment, surface supplied diving equipment, recompression chambers, high-altitude mountaineering, high-flying aircraft, submarines ...

  7. Atmosphere of Earth - Wikipedia

    en.wikipedia.org/wiki/Atmosphere_of_Earth

    Air pollution is the introduction of airborne chemicals, particulate matter or biological materials that cause harm or discomfort to organisms. [53] The population growth , industrialization and motorization of human societies have significantly increased the amount of airborne pollutants in the Earth's atmosphere, causing noticeable problems ...

  8. Gas - Wikipedia

    en.wikipedia.org/wiki/Gas

    Drifting smoke particles indicate the movement of the surrounding gas.. Gas is one of the four fundamental states of matter.The others are solid, liquid, and plasma. [1] A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or compound molecules made from a variety of atoms (e.g. carbon dioxide).

  9. Particulates - Wikipedia

    en.wikipedia.org/wiki/Particulates

    Particulates or atmospheric particulate matter (see below for other names) are microscopic particles of solid or liquid matter suspended in the air. The term aerosol refers to the particulate/air mixture , as opposed to the particulate matter alone, [ 1 ] though it is sometimes defined as a subset of aerosol terminology. [ 2 ]