Kelvin scale, absolute zero

Figure 3.10 Temperature scales Celsius and Kelvin (absolute). On the Celsius scale, absolute zero is -273 °C. The temperature at which water boils is, therefore, 373 °K. Most life on earth exists only between 277 and 293 °K.

ABSOLUTE ZERO. Conceptually that temperature where there is no molecular motion, no heat. On the Celsius scale, absolute zero is -273.15°C, on the Fahrenheit scale, —459.67°F and zero Kelvin (0 K). The concept of absolute zero stems from thermodynamic postulations,... 

Absolute temperature temperature measured on a scale with absolute zero as 0. This is conventionally measured in kelvin, where absolute zero corresponds to 0 K (—273.15°C or -459.67°F). 

The Kelvin scale is the SI temperature scale, and the SI unit of temperature is the kelvin (K). Zero on the Kelvin scale is the lowest attainable temperature, referred to as absolute zero. On the Celsius scale, absolute zero has the value, -273.15 °C. The Celsius and Kelvin scales have equal-sized units—that is, a kelvin is the same size as a degree Celsius. Thus, the Kelvin and Celsius scales are related according to... 

Temperature is usually measured in Celsius (°C), Fahrenheit (°F) or Kelvin (K). The Celsius and the Fahrenheit scales are empirical but (as we shall see in Chapter 3) the Kelvin scale is the absolute scale based on the second law of thermodynamics. Zero degrees Kelvin is absolute zero, the lowest possible temperature. Temperatures measured in these scales are related as follows ... 

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. 

Carnot s research also made a major contribution to the second law of thermodynamics. Since the maximum efficiency of a Carnot engine is given by 1 -T( H, if the engine is to be 100 percent efficient (i.e., Cma = 1), Tc must equal zero. This led William Thomson (Lord Kelvin) to propose in 1848 that Tf must be the absolute zero of the temperature scale later known as the absolute scale or Kelvin scale. ... 

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. 

Absolute temperature, 57 Kelvin scale, 58 Absolute zero, 58... 

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). 

Kelvin then replotted his data, this time extrapolating each graph till the volume of the gas was zero, which he found to occur at a temperature of -273.15 °C see Figure 1.5. He then devised a new temperature scale in which this, the coldest of temperatures, was the zero. He called it absolute zero, and each subsequent degree was equal to 1 °C. This new scale of temperature is now called the thermodynamic (or absolute) scale of temperature, and is also sometimes called the Kelvin scale. 

Celsius degrees and Kelvin degrees are the same size. The Kelvin scale begins at absolute zero. This is the temperature at which the particles in a substance have no kinetic energy. Therefore, Kelvin temperatures are never negative. By contrast, 0°C is set at the melting point of water. Celsius temperatures can be positive or negative. 

Kelvin scale a temperature scale that begins at the theoretical point of absolute zero kinetic energy, or -273.15°C each unit (a kelvin) is equal to 1°C... 

Absolute zero. Minus 273°C or minus 460 or 0°K or Kelvin, the scale used in theoretical physics and chemistry. Absolute zero is the theoretical temperature at which all molecular activity ceases. In practical terms, the lowest reachable temperature is about 1°K. 

When a gas is cooled by 1 °C, from 0°C to —1 °C, it loses l4 3 of its pressure. Since pressure is due to movement of the gas molecules, Lord Kelvin realised that a gas would have no pressure at -273 °C that is, there would be no movement of the gas molecules -273 °C is absolute zero. Since the rate of a reaction depends upon the movement and hence collision of molecules, the relevant temperature scale for chemical (and therefore biochemical) reactions is one whose zero is -273 °C. It is known as the Kelvin or absolute scale. 

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 ... 

Lord Kelvin (1824-1907). The Kelvin temperature scale has an absolute zero. True comparisons can be made using the Kelvin scale. A substance at a temperature of 400 Kelvins contains particles with twice as much kinetic energy as a substance at 200 Kelvins. Absolute zero is the temperature where the random motion of particles in a substance stops. It is the absence of temperature. Absolute zero is equivalent to —273.16°C. How this value is determined is discussed shortly after we discuss our next gas law. The relationship between Kelvin and Celsius temperature is... 

Absolute Zero 0 Kelvins or-273.15°C, the lowest possible temperature, the point on the temperature scale where all molecular motion ceases... 

This declaration had at least two immediate benefits. First, it happened to be correct. Second, it allowed Kelvin to create the Kelvin temperature scale, with absolute zero as the Official Zero. Using the Kelvin scale (where °C = K- 273), everjdhing makes a whole lot more sense. For example, doubling the Kelvin temperature of a gas doubles the volume of that gas. 

Knowledge of the numerical value of the entity represented by Eq. (9.1) allows one to make up cells that give the potential of an electrode "on the absolute scale, just as the Celsius scale was later shown to be expressed on the absolute or Kelvin scale of temperatures, in which there is a rationally based zero at -273 °C. Thus, to find the absolute value, VM>abs of an electrode potential expressed on the standard hydrogen scale, one writes... 

As defined by (4.19) or (4.21), it is easy to recognize that TK is an absolute (strictly non-negative) quantity. Furthermore, one can see from (4.19) that the highest possible efficiency ( —> 1) is achievable only at the absolute zero of the Kelvin scale (7"cK —> 0). In addition, the lowest efficiency of converting heat to work ( —> 0) occurs when the two reservoirs approach the same temperature (7j —> 7"cK), consistent with the statement of Kelvin s principle in Section 4.4. Such limits on engine efficiency can be used to paraphrase the three laws of thermodynamics in somewhat whimsical form as follows (the ultimate formulation of the no free lunch principle) ... 

A temperature scale favored by scientists is the Kelvin scale, named after the British physicist Lord Kelvin (1824—1907). This scale is calibrated not in terms of the freezing and boiling points of water, but rather in terms of the motion of atoms and molecules. On the Kelvin scale, zero is the temperature at which there is no atomic or molecular motion. This is a theoretical limit called absolute zero, which is the temperature at which the particles of a substance... 

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