Absolute Temperature Scales

The absolute temperature scale that corresponds to the Celsius scale is the Kelvin scale for the Fahrenheit scale, the absolute scale is called the Rankine scale. The Celsius scale reads 0 when the Kelvin scale reads 273 the Fahrenheit scale reads 0 when the Rankine scale reads 460. These relationships are shown in Figure 1. 

The volume of a gas would theoretically be zero at a temperature of approximately -273°C or -460°F. Tliis temperature, wliich lias become known as absolute zero, is tlie basis for tlie definition of two absolute temperature scales, tlie Kelvin (K) and Rankine (°R) scales. The former is defined by shifting tlie Celsius scale by 273-Celsius degrees so that 0 K is equal to -273°C. Equation (4.2.3) shows tliis relation. 

This relation is used to define the absolute temperature scale in terms of energy exchanged with reser-... 

In the study of refrigeration, the Kelvin or absolute temperature scale is also used. This starts at absolute zero and has the same degree intervals as the Celsius scale, so that ice melts at + 2 73.16 K and water at atmospheric pressure boils at + 373.15 K. 

Fig. 4-5. An absolute temperature scale from the change of volume of a gas with temperature.

There are great advantages to an absolute temperature scale that has its zero point at — 273°C. Whereas the zero of temperature in the Centigrade scale is based upon an arbitrary temperature, selected because it is easily measured, the zero point of the absolute scale has inherent significance in the kinetic theory. If we express temperatures on an absolute temperature scale, we find that the volume of a fixed amount of gas (at constant pressure) varies directly with temperature Also, the pressure of a fixed amount of (at constant volume) varies directly with temperature. And, according to the kinetic theory, the kinetic energy of the molecules varies directly with the absolute temperature. For these reasons, in dealing with gas relations, we shall usually express temperature on an absolute temperature scale. 

We have remarked that a temperature of zero on the absolute temperature scale would correspond to the absence of all motion. The kinetic energy would become zero. Very interesting phenomena occur at temperatures near 0°K (the superconductivity of many metals and the superfluidity of liquid helium are two examples). Hence, scientists are extremely interested in methods of reaching temperatures as close to absolute zero as possible. Two low temperature coolants commonly used are liquid hydrogen (which boils at 20°K) and liquid helium (which boils at 4°K). Helium, under reduced pressure, boils at even lower temperatures and provides a means of reaching temperatures near 1°K. More exotic techniques have been developed to produce still lower temperatures (as low as 0.001°K) but even thermometry becomes a severe problem at such temperatures. 

The Absolute Temperature Scale The absolute temperature scale is based on the (p, V, T) relationships for an ideal gas as given by equation (1.7)... 

The proportionality constant is arbitrary and can be set at any number. We set it equal to one so that the Kelvin and absolute temperature scales are the same. 

Absolute temperature The lowest possible temperature is absolute zero. The absolute temperature scale starts there and increases in increments of 1 degree Celsius. The unit of measurement is the kelvin (K). 

In studying interfacial electrochemical behavior, especially in aqueous electrolytes, a variation of the temperature is not a common means of experimentation. When a temperature dependence is investigated, the temperature range is usually limited to 0-80°C. This corresponds to a temperature variation on the absolute temperature scale of less than 30%, a value that compares poorly with other areas of interfacial studies such as surface science where the temperature can easily be changed by several hundred K. This "deficiency" in electrochemical studies is commonly believed to be compensated by the unique ability of electrochemistry to vary the electrode potential and thus, in case of a charge transfer controlled reaction, to vary the energy barrier at the interface. There exist, however, a number of examples where this situation is obviously not so. 

The relationship between temperatures T on the centigrade and the absolute temperature scales is given by... 

Absolute pressure transducers, 20 657 Absolutes, in perfumes, 18 365 Absolute system of dimensions, 8 584 Absolute temperature scale, 24 283 Absolute viscosity, exponents of dimensions in absolute, gravitational, and engineering systems, 8 584t Absorbable sutures... 

Also known as anhydrous alcohol. ab-s3,lut ahko-hol absolute boiling point chem The boiling point of a substance expressed in the unit of an absolute temperature scale. ab-s3,lut boihiri, point absolute configuration org chem The three-dimensional arrangement of substituents around a chiral center in a molecule. Also known as absolute stereochemistry. ab-s3 lut k3n,fig-y3 ra-shon ... 

A temperature measured on an absolute temperature scale (i.e., a scale in which zero degrees is equivalent to absolute zero). In the Kelvin scale, the degree unit is the kelvin, abbreviated as K it does not have the superscript o used to indicate degree as on the Celsius scale. K has the same magnitude as degree Celsius (°C). 

Because the volume of a gas decreases with falling temperature, scientists realized that a natural zero-point for temperature could be defined as the temperature at which the volume of a gas theoretically becomes zero. At a temperature of absolute zero, the volume of an ideal gas would be zero. The absolute temperature scale was devised by the English physicist Kelvin, so temperatures on this scale are called Kelvin (K) temperatures. The relationship of the Kelvin scale to the common Celsius scale must be memorized by every chemistry student ... 

The most common absolute temperature scale used by scientists is the Kelvin temperature scale. The Kelvin temperature scale was proposed by William Thompson,... 

William entered Cambridge at the age of 16, earning high honors in mathematics. Early in 1846, just prior to his permanent appointment as Professor of Natural Philosophy at Glasgow (at age 22 ), he spent a few months in the laboratory of H. G. Regnault in Paris. There he apparently learned of Clapeyron s 1834 paper and, indirectly, of Carnot s Reflexions, which he was unable to find in Paris. Thomson was finally able to obtain and read Carnot s work in 1848, and it became the acknowledged basis for his initial 1848 proposal of the absolute temperature scale (corrected in 1854 to that used today). 

Kelvin first suggested how the Carnot efficiency (4.9) might be used to define an absolute temperature scale. As Carnot s principle asserts, the efficiency... 

An absolute scale is obtained by choosing Equation (2). Depending on the value assigned to a, we obtain the Kelvin or Rajtkine scale. The Kelvin absolute temperature scale assigns to the triple point of water the value... 

When converting to the absolute temperature scale T, it is important to recognize the convention 0°C — 273.15 K. The constants A and B in Eq. (3) are determined empirically from experimental data by plotting log P versus 1 /T and taking the slope as —A and the intercept at 1/T = 0 as B. Equation (2) is found to yield a fairly accurate fit to vapor pressure data for highly volatile substances and is often perfectly adequate for moderately accurate data below the boiling point. 

The SI unit of temperature is so defined that 0 K is the absolute zero of temperature. The SI or Kelvin scale is often called the absolute temperature scale. Although absolute zero does not appear to be attainable, it has been approached to within 10-4 K. 

Actually, there are other absolute temperature scales, but the Kelvin scale is the official SI measure of temperature. 

The Kelvin scale is an absolute temperature scale that begins at the lowest possible temperature, which is absolute zero, although we can never reach this temperature. The temperature change corresponding to 1 K is equal to a change of 1°C. 

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