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Starch

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Starch , common name applied to a white, granular or powdery, odorless, tasteless, complex carbohydrate, (C 6 H 10 O 5 ) x , abundant in the seeds of cereal plants and in bulbs and tubers. Molecules of starch are made of hundreds or thousands of atoms, corresponding to values of x, as given in the formula above, that range from about 50 to many thousands. Starch molecules are of two kinds. In the first kind, amylose, which constitutes about 20 percent of ordinary starch, the C 6 H 10 O 5 groups are arranged in a continuous but curled chain somewhat like a coil of rope; in the second kind, amylopectin, considerable side-branching of the molecule occurs. Starch is manufactured by green plants during the process of photosynthesis . It forms part of the cell walls in plants, constitutes part of rigid plant fibers, and serves as a kind of energy storage for plants, because its oxidation to carbon dioxide and water releases energy. The granules of starch present in any
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Dextrin

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Dextrin , amorphous, soluble carbohydrate, (C 6 H 10 O 5 ) n , produced by the action on starch paste of acids, heat, or enzymes such as diatase. The first product formed in this reaction is soluble starch, which in turn hydrolyzes to form dextrin. Dextrin is prepared commercially by moistening potato starch with weak nitric acid and then drying and heating the mass at 110° C (230° F). Dextrin is used in the manufacture of beer and as a substitute for gum arabic in printing cotton fabrics. It is also used commercially as an adhesive.
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Hydrolysis

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Hydrolysis , type of chemical reaction in which a molecule of water , formula HOH, reacts with a molecule of a substance AB, in which A and B represent either atoms or groups of atoms. In the reaction the water molecule breaks into the fragments H + and OH - ; and the molecule AB breaks into A + and B - ; the fragments then join to give the final products AOH and HB. This kind of reaction is called a double decomposition or an exchange.
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The Quantum Explanation of Spectral Lines

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The explanation for exact spectral lines for each substance was provided by the  quantum theory . In his 1913 model of the hydrogen atom Niels Bohr showed that the observed series of lines could be explained by assuming that electrons are restricted to atomic orbits in which their orbital angular momentum is an integral multiple of the quantity   h /2Ï€, where  h  is Planck's constant. The integer multiple (e.g., 1, 2, 3 …) of  h /2Ï€ is usually called the quantum number and represented by the symbol  n. When an electron changes from an orbit of higher energy (higher angular momentum) to one of lower energy, a  photon  of light energy is emitted whose frequency ν is related to the energy difference Δ E  by the equation ν=Δ E / h. For hydrogen, the frequencies of the spectral lines are given by ν= cR  (1/ n f 2 −1/ n i 2 ) where  c  is the speed of light,  R is the Rydberg constant, and  n f  and  n i  are the final and initial quantum numbers of the electron orbits ( n i  is always
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Spectrum

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Spectrum, arrangement or display of light or other form of radiation separated according to wavelength, frequency, energy, or some other property. Beams of charged particles can be separated into a spectrum according to mass in a mass spectrometer (see mass spectrograph ). Physicists often find it useful to separate a beam of particles into a spectrum according to their energy. Continuous and Line Spectra Dispersion, the separation of visible light into a spectrum, may be accomplished by means of a prism or a diffraction grating. Each different wavelength or frequency of visible light corresponds to a different color , so that the spectrum appears as a band of colors ranging from violet at the short-wavelength (high-frequency) end of the spectrum through indigo, blue, green, yellow, and orange, to red at the long-wavelength (low-frequency) end of the spectrum. In addition to visible light, other types of electromagnetic radiation may be spread into a spectrum according to
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Conservation Laws

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Conservation laws, in physics, basic laws that together determine which processes can or cannot occur in nature; each law maintains that the total value of the quantity governed by that law, e.g., mass or energy, remains unchanged during physical processes. Conservation laws have the broadest possible application of all laws in physics and are thus considered by many scientists to be the most fundamental laws in nature. Conservation of Classical Processes Most conservation laws are exact, or absolute, i.e., they apply to all possible processes; a few conservation laws are only partial, holding for some types of processes but not for others. By the beginning of the 20th cent. physics had established conservation laws governing the following quantities: energy, mass (or matter), linear momentum, angular momentum , and electric charge. When the theory of relativity showed (1905) that mass was a form of energy, the two laws governing these quantities were combined into a single l
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Momentum

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Momentum, in mechanics, the quantity of motion of a body, specifically the product of the mass of the body and its velocity . Momentum is a vector quantity; i.e., it has both a magnitude and a direction, the direction being the same as that of the velocity vector. When an external force acts upon a body or a system of bodies in motion, it causes a change in the momentum of the body. The impulse of a force acting on a body is the product of the force and the duration of time in which it acts and is equal to the change in momentum of the body. When no external force acts upon a body in motion or a system of bodies there is no change in the total momentum even though, as in the case of a system of bodies, there may be an internal disturbance of the system resulting in changes in the momenta of individual bodies. This conclusion is commonly known as the principle of the conservation of momentum (see conservation laws , in physics). The momentum of a body should not be confused with its ki
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