Kids Research Express

. Food Web, set of interconnected food chains by which energy and materials circulate within an ecosystem (see Ecology ). The food web is divided into two broad categories: the grazing web, which typically begins with green plants, algae , or photosynthesizing plankton , and the detrital web, which begins with organic debris. These webs are made up of individual food chains. In a grazing web, materials typically pass from plants to plant eaters (herbivores) to flesh eaters (carnivores). In a detrital web, materials pass from plant and animal matter to bacteria and fungi (decomposers), then to detrital feeders (detritivores), and then to their predators (carnivores). Food Web The sun is the original source of energy in virtually all ecosystems. Producers (plants) convert the light energy into chemical energy, storing it in their cells. When primary consumers (herbivores) eat the producers, the energy changes into a form that can be stored in animal cells. Secondary consumers (carniv

. Metabolism (chemistry), inclusive term for the chemical reactions by which the cells of an organism transform energy, maintain their identity, and reproduce. All life forms—from single-celled algae to mammals—are dependent on many hundreds of simultaneous and precisely regulated metabolic reactions to support them from conception through growth and maturity to the final stages of death. Each of these reactions is triggered, controlled, and terminated by specific cell enzymes or catalysts, and each reaction is coordinated with the numerous other reactions throughout the organism. ANABOLISM AND CATABOLISM Two metabolic processes are recognized: anabolism and catabolism. Anabolism, or constructive metabolism, is the process of synthesis required for the growth of new cells and the maintenance of all tissues. Catabolism, or destructive metabolism, is a continuous process concerned with the production of the energy required for all external and internal physical activity. Catabolism also

. Nylon, term applied to a synthetic resin widely used for textile fibers, characterized by great strength, toughness, and elasticity, and processed also in the form of bristles and molded articles. Nylon was developed in the 1930s by scientists of Eleuthère Irénée du Pont de Nemours, headed by the American chemist Wallace Hume Carothers. It is usually made by polymerizing adipic acid and hexamethylenediamine, an amine derivative. Adipic acid is derived from phenol; hexamethylenediamine is made by treating adipic acid catalytically with ammonia and hydrogenating the product Hydrogenation. Nylon is insoluble in water and in ordinary organic solvents; it dissolves in phenol, cresol, and formic acid, and melts at 263° C (505° F). In making textile fibers, small chips of the nylon polymer, which is obtained as a tough, ivorylike material, are melted and forced through holes in a metal disk called a spinneret. The filaments are congealed by a blast of air and are then drawn to about four ti

. Butane, either of two saturated hydrocarbons, or alkanes, In both compounds the carbon atoms are joined in an open chain. In n-butane (normal), the chain is continuous and unbranched whereas in i-butane (iso) one of the carbon atoms forms a side branch. This difference in structure results in small but distinct differences in properties. Thus, n-butane melts at -138.3° C (-216.9° F) and boils at -0.5° C (31.1° F), and i-butane melts at -145° C (-229° F) and boils at -10.2° C (13.6° F). Both butanes occur in natural gas, petroleum, and refinery gases. They show little chemical reactivity at ordinary temperatures but burn readily when ignited in air or oxygen. They make up the most volatile portion of gasoline and are sometimes added to propane to be marketed as bottled gas. Most n-butane, however, is converted to butadiene , which is used to make synthetic rubber and latex paints.

. Butadiene, synthetic chemical compound, used principally in the manufacture of synthetic rubber , nylon , and latex paints. Most commercial butadiene is made by dehydrogenation of butene or of mixtures of butene and butane ; it may also be made from ethanol. Because butadiene has high reactivity, it is useful in synthesis, particularly in polymerization reactions. A large percentage of automobile tires are made from Buna rubber, a copolymer of butadiene and styrene. Butadiene is a colorless, gaseous hydrocarbon. It is liquefied by cooling to -4.4° C (24.1° F) or by compression to 2.8 atmospheres at 25° C (77° F).

. Phenol, formerly called carbolic acid, aromatic organic compound. It is weakly acidic and resembles the alcohols in structure. The colorless, needlelike crystals of purified phenol melt at 43° C (109° F) and boil at 182° C (360° F). During storage the crystals become pink and finally reddish brown. Phenol is soluble in organic solvents and slightly soluble in water at room temperature, but infinitely soluble above 66° C (150.8° F). It is a constituent of coal tar. Phenol was first used as a disinfectant in 1867 by the British surgeon Joseph Lister for sterilizing wounds, surgical dressings, and instruments. Dilute solutions are useful antiseptics, but strong solutions are caustic and scarring to tissue. Less irritating and more efficient germicides have replaced phenol, but it is widely used in the manufacture of resins , plastics , insecticides, explosives , dyes, and detergents, and as raw material for the production of medicinal drugs such as aspirin . A phenol derivative, phenolp

. Tear Gas, chemical substance that produces a primary physical effect of stinging or tearing eyes. Tear gas also irritates other mucous membranes and causes choking and coughing. People exposed to higher concentrations may experience burning, itching, or even blistering skin. As a form of riot control, police often use clouds of tear gas to break up crowds of people. A rifle-fired grenade or a thrown canister usually delivers tear gas, but smaller hand-held spray devices also exist. Tear gas may also be used to force the surrender of fugitives hiding in a building. Dogs and horses are relatively unaffected by tear gas, so they can add to the riot-control effect of the gas. TYPES OF TEAR GAS CN and CS are the two main types of tear gas. CN’s scientific name is chloroacetophenone, and it comes in several variants. CNB adds benzene and carbon tetrachloride, while CNC adds chloroform. CNS adds chloropicrin (PS), which can cause victims to vomit or suffer lung damage. CN was discovered in