Showing posts with label temperature. Show all posts
Showing posts with label temperature. Show all posts

Friday, January 15, 2010

Calorie

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a unit of quantity of heat defined as that heat needed to raise the temperature of one gram of water through 1°C. Nowadays, it has largely been replaced by the JOULE (1 calorie = 4.186 joules).

Taken from Dictionary of Science

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The calorie is a pre-SI metric unit of energy. The unit was first defined by Professor Nicolas Clément in 1824 as a unit of heat. This definition entered French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule. However, in many countries it remains in common use as a unit of food energy. The kilocalorie per mole remains in use in computational chemistry and molecular spectroscopy.


Definitions vary but are all based on the specific heat capacity of water. The gram calorie, approximately 4.2 J, is based on one gram of water. The kilogram calorie, equal to one thousand gram calories, is based on one kilogram of water. In the context of nutrition, and especially food labelling, a larger unit is used and referred to interchangeably by the terms calorie (or Calorie) and kilocalorie.


Taken from Wikipedia



Thursday, January 14, 2010

Taxis


(plural taxes) the movement of a cell or organism in response to a stimulus in environment. This stimulus may be temperature (thermotaxis), light (phototaxis), gravity (geotaxis) or chemical (CHEMOTAXIS).

Taken from Dictionary of Science

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A taxis (plural taxes, pronounced /ˈtæksiːz/) is an innate behavioral response by an organism to a directional stimulus or gradient of stimulus intensity. A taxis differs from a tropism (turning response, often growth towards or away from a stimulus) in that the organism has motility and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus that results in the migration toward or away from a stimulus.

Taken from Wikipedia

Tuesday, January 12, 2010

Absolute Zero


the temperature at which the particles that make up matter have no energy at all whether due to heat or motion. It is theoretically given the value of -273.15°Celsius (-459.67° Fahrenheit).

Taken from Dictionary of Science
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Absolute zero is the temperature at which entropy reaches its minimum value. As implied by the laws of thermodynamics, absolute zero cannot be reached by artificial or natural means because this would require a system to be fully removed from the rest of the universe. A system at theoretical absolute zero possesses quantum mechanical zero-point energy. While all molecular motion does not cease at absolute zero, the system does not have enough energy for transference to other systems. It is therefore correct to say that molecular energy is minimal at absolute zero.


By international agreement, absolute zero is defined as precisely 0 K on the Kelvin scale and as −273.15° on the Celsius scale. Absolute zero is also precisely equivalent to 0 R on the Rankine scale (same as Kelvin but measured in Fahrenheit intervals) and −459.67° on the Fahrenheit scale. Though it is not theoretically possible to cool any substance to 0 K, scientists have made great advancements in achieving temperatures close to absolute zero, where matter exhibits quantum effects such as superconductivity and superfluidity.


For the kinematics of molecules at absolute zero on a larger scale, which is easier to understand, see kinetic energy.


Taken from Wikipedia

Thursday, January 7, 2010

Kaolinization


the high temperature hydrothermal alteration and breakdown of FELDSPARS to form KAOLINITE. The process can proceed in granites to the point where the rock literally falls apart and the only recognizable, original mineral is quartz.

Taken from Dictionary of Science

Tuesday, January 5, 2010

Fahrenheit


(F) a temperature scale, devised by the German physicist Gabriel Fahrenheit (1686-1736), that set the freezing point of water at 32º and the boiling point at 212º. Fahrenheit temperatures can be converted to CELSIUS by the equation F = 1.8C + 32.

Taken from Dictionary of Science

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Fahrenheit is the temperature scale proposed in 1724 by, and named after, the physicist Daniel Gabriel Fahrenheit (1686–1736). Today, the temperature scale has been replaced by the Celsius scale in most countries. It is still in use for non-scientific purposes in the United States and a few other nations, such as Belize.


Taken from Wikipedia