Kelvin, defined

Kelvin, defined, 24 434-435 Kelvin, Lord, 24 433 Kelvin equation, 9 113 19 182 Kelvin-Helmholtz instability, 11 762-763, 765, 772... 

The term chirality (from the Greek kheir = hand) was introduced by the Scottish scientist, Lord Kelvin, a few years after Pasteur s separation of the enantiomers of tartaric acid [1]. Kelvin defined chirality as a property of... 

The equilibrium vapour pressure, P, over a curved surface is defined by tlie Kelvin equation... 

Temperature kelvin K Defined as the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. 

The ultimate definition of thermodynamic temperature is in terms of pV (pressure X volume) in a gas thermometer extrapolated to low pressure. The kelvin (K), the unit of thermodynamic temperature, is defined by specifying the temperature of one fixed point on the scale—the triple point... 

The procedures described so far have all required a pore model to be assumed at the outset, usually the cylinder, adopted on the grounds of simplicity rather than correspondence with actuality. Brunauer, Mikhail and Bodor have attempted to eliminate the over-dejjendence on a model by basing their analysis on the hydraulic radius r rather than the Kelvin radius r . The hydraulic radius is defined as the ratio of the cross-sectional area of a tube to its perimeter, so that for a capillary of uniform cross-section r is equal to the ratio of the volume of an element of core to... 

Chapter 3, there is often a region immediately preceding the lower closure point, in which increased adsorption is brought about by reversible capillary condensation. The meniscus now tends to be somewhat ill defined owing to its small dimensions (p. 153), but the mechanism can still be thought of in Kelvin terms, where the driving force is the pressure difference across an interface. 

A vast amount of research has been undertaken on adsorption phenomena and the nature of solid surfaces over the fifteen years since the first edition was published, but for the most part this work has resulted in the refinement of existing theoretical principles and experimental procedures rather than in the formulation of entirely new concepts. In spite of the acknowledged weakness of its theoretical foundations, the Brunauer-Emmett-Teller (BET) method still remains the most widely used procedure for the determination of surface area similarly, methods based on the Kelvin equation are still generally applied for the computation of mesopore size distribution from gas adsorption data. However, the more recent studies, especially those carried out on well defined surfaces, have led to a clearer understanding of the scope and limitations of these methods furthermore, the growing awareness of the importance of molecular sieve carbons and zeolites has generated considerable interest in the properties of microporous solids and the mechanism of micropore filling. 

Celsius temperature degree Celsius °c equal to kelvin and used in place of kelvin for expressing Celsius temperature, t, defined by equation t = T — where T is the thermodynamic temperature and Tq = 273.15 K by definition... 

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. 

Thermal conductivity, now denoted by the Greek letter lambda (previously known as the fc-value), defines a material s ability to transmit heat, being measured in watts per square meter of surface area for a temperature gradient of one Kelvin per unit thickness of one meter. For convenience in practice, its dimensions Wm/m K be reduced to W/mK, since thickness over area mluF cancels to 1/m. 

For many purposes in chemistry, the most convenient unit of temperature is the ketvin (K) note the absence of the degree sign. The kelvin is defined to be 1/273.16 of the difference between the lowest attainable temperature (0 K) and the triple point of water (0.01°C). The relationship between temperature in K and in °C is... 

The size of the degree alone remains to be fixed, and is quite arbitrary. To produce as little change as possible from the ordinary scale, Lord Kelvin divided the range of temperature between the absolute temperature of melting ice T0, and that of boiling water, Ti, into 100 equal parts, each of which is defined as one degree. 

It was Lord Kelvin who recognized that Carnot s hypothetical engine was of fundamental importance, and used it to define a thermodynamic scale of temperature that has become known as the Kelvin temperature. He set the thermodynamic temperature T of the reservoirs proportional to the amount of heat exchanged at each that is. 

In the next chapter, we will return to the Carnot cycle, describe it quantitatively for an ideal gas with constant heat capacity as the working fluid in the engine, and show that the thermodynamic temperature defined through equation (2.34) or (2.35) is proportional to the absolute temperature, defined through the ideal gas equation pVm = RT. The proportionality constant between the two scales can be set equal to one, so that temperatures on the two scales are the same. That is, 7 °Absolute) = T(Kelvin).r... 

We wish to show that no points to the leftbb of 2 on the isotherm 62 are accessible from point 1 via any adiabatic path, reversible or irreversible. Suppose we assume that some adiabatic path does exist between 1 and 2. We represent this path as a dotted curve in Figure 2.11a. We then consider the cycle I —>2 —> 1 — 1. The net heat associated with this cycle would be that arising from the last step 1 — 1, since the other two steps are defined to be adiabatic. We have defined the direction 1 — 1 to correspond to an absorption of heat, which we will call qy. From the first law, the net work vv done in the cycle, is given by w = —q, since AU for the cycle is zero. Thus, for this process, iv is negative (and therefore performed by the system), since qy is positive, having been absorbed from the reservoir. The net effect of this cycle, then, is to completely convert heat absorbed at a high temperature reservoir into work. This is a phenomenon forbidden by the Kelvin-Planck statement of the Second Law. Hence, points to the left of 2 cannot be reached from point 1 by way of any adiabatic path. 

We have already shown that the absolute temperature is an integrating denominator for an ideal gas. Given the universality of T 9) that we have just established, we argue that this temperature scale can serve as the thermodynamic temperature scale for all systems, regardless of their microscopic condition. Therefore, we define T, the ideal gas temperature scale that we express in degrees absolute, to be equal to T 9), the thermodynamic temperature scale that we express in Kelvins. That this temperature scale, defined on the basis of the simplest of systems, should function equally well as an integrating denominator for the most complex of systems is a most remarkable occurrence. 

Figure 11.11. Correlation between the equivalent potentials of the supports defined in Figure 11.10 and of the work function or absolute potential of the supports measured via the Kelvin probe technique in po2 =1 atm at 400°C.22...

A triple point is a point where three phase boundaries meet on a phase diagram. For water, the triple point for the solid, liquid, and vapor phases lies at 4.6 Torr and 0.01°C (see Fig. 8.6). At this triple point, all three phases (ice, liquid, and vapor) coexist in mutual dynamic equilibrium solid is in equilibrium with liquid, liquid with vapor, and vapor with solid. The location of a triple point of a substance is a fixed property of that substance and cannot be changed by changing the conditions. The triple point of water is used to define the size of the kelvin by definition, there are exactly 273.16 kelvins between absolute zero and the triple point of water. Because the normal freezing point of water is found to lie 0.01 K below the triple point, 0°C corresponds to 273.15 K. 

Integers and exact numbers In multiplication or division by an integer or an exact number, the uncertainty of the result is determined by the measured value. Some unit conversion factors are defined exactly, even though they are not whole numbers. For example, 1 in. is defined as exactly 2.54 cm and the 273.15 in the conversion between Celsius and Kelvin temperatures is exact so 100.000°C converts into 373.150 K. 

International System (SI) in terms of which all other units are defined. Examples kilogram for mass meter for length second for time kelvin for temperature ampere for electric current, basic ion An ion that acts as a Bronsted base. 

Scientists use two units for temperature, the Celsius (°C) scale and the Kelvin (K) scale. These scales are shown schematically in Figure 1-18. Unlike other scientific units, the unit size of the Celsius and Kelvin scales is the same, but their zero points differ. For both scales, the difference in temperature between the freezing and boiling points of water is defined to be 100 units. However, the temperature at which ice melts to liquid water is 0 °C and 273.15 K. 

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