temperature

/tem"peuhr euh cheuhr, -choor', -preuh-, -peuhr cheuhr, -choor'/, n.

1. a measure of the warmth or coldness of an object or substance with reference to some standard value. The temperature of two systems is the same when the systems are in thermal equilibrium.

2. Physiol., Pathol.

a. the degree of heat in a living body, normally about 98.6°F (37°C) in humans.

b. the excess of this above the normal.

3. Obs. mildness, as of the weather.

4. Obs. temperament.

[1525-35; < L temperatura a tempering. See TEMPERATE, -URE]

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Measure of hotness expressed in terms of any of several arbitrary scales, such as Fahrenheit, Celsius, or Kelvin.

Heat flows from a hotter body to a colder one and continues to do so until both are at the same temperature. Temperature is a measure of the average energy of the molecules of a body, whereas heat is a measure of the total amount of thermal energy in a body. For example, whereas the temperature of a cup of boiling water is the same as that of a large pot of boiling water (212°F, or 100°C), the large pot has more heat, or thermal energy, and it takes more energy to boil a pot of water than a cup of water. The most common temperature scales are based on arbitrarily defined fixed points. The Fahrenheit scale sets 32° as the freezing point of water and 212° as the boiling point of water (at standard atmospheric pressure). The Celsius scale defines the triple point of water (at which all three phases, solid, liquid, and gas, coexist in equilibrium) at 0.01° and the boiling point at 100°. The Kelvin scale, used primarily for scientific and engineering purposes, sets the zero point at absolute zero and uses a degree the same size as those of the Celsius scale.

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▪ physics

      measure of hotness or coldness expressed in terms of any of several arbitrary scales and indicating the direction in which heat energy will spontaneously flow, i.e., from a hotter body (one at a higher temperature) to a colder body (one at a lower temperature). Temperature is not the equivalent of the energy of a thermodynamic system (thermodynamics); e.g., a burning match is at a much higher temperature than an iceberg, but the total heat energy contained in an iceberg is much greater than the energy contained in a match. Temperature, like pressure or density, is called an intensive property—one that is independent of the quantity of matter being considered—as distinguished from extensive properties such as mass or volume.

 Three temperature scales are in general use today. The Fahrenheit (°F) temperature scale (Fahrenheit temperature scale) is used in the United States and a few other English-speaking countries. The Celsius (°C) temperature scale (Celsius temperature scale) is standard in virtually all countries that have adopted the metric system of measurement, and it is widely used in the sciences. The Kelvin (K) scale (kelvin), an absolute temperature scale (obtained by shifting the Celsius scale by −273.15° so that absolute zero coincides with 0 K), is recognized as the international standard for scientific temperature measurement. In certain fields of engineering, another absolute temperature scale, the Rankine scale (see William Rankine (Rankine, William John Macquorn)), is preferred over the Kelvin scale. Its unit of measure—the degree Rankine (°R)—equals the Fahrenheit degree, as the kelvin equals one Celsius degree. A scale rarely used in recent years is the Réaumur (°Re) temperature scale (Réaumur temperature scale). See the table—> for details on the relationships between these various temperature scales and instructions for converting values from one scale to another.

 

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