Zero points, temperature scales

There are two main types of quantitative data discrete and continuous. Discrete quantitative data usually come about by the counting of numbers of events. Examples of this form of data are the number of asthma attacks, the numbers of rescue tablets taken, the number of relapse events, etc. There are two types of continuous quantitative data defined by, whether there is a true zero point of the scale or not. If there is such a zero point the scale is a ratio scale, otherwise it is an interval scale. Examples of the former are height, weight or volume, etc, while a typical example of the latter is temperature in which the origin is essentially arbitrary - 0°F is... 

From these examples the construction of this scale is apparent, and, as a corollary, it should be noted that the oxygen potentials of CO/CO2 mixtures can be obtained by joining the point marked C on the left-hand side of the diagram, at the absolute zero of temperature, with the appropriate CO/CO2 ratios marked on the scale at the right-hand side of the diagram. 

The general temperature scale now in use is the Celsius scale, based nominally on the melting point of ice at 0°C and the hoiling point of water at atmospheric pressure at 100°C. (By strict definition, the triple point of ice is 0.01°C at a pressure of 6.1 mhar.) On the Celsius scale, absolute zero is -2 73.15°C. 

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. 

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. 

Celsius and Kelvin temperature scales. Kelvins and degrees Celsius have the same unit size but different zero points. Room temperature is typically about 295 K (22 °C). ... 

Any data series that includes zero as a point on a larger scale, for example the centigrade temperature scale. 

It is interesting to contrast the rate ratio for reactions 10.1 and 10.4 where either H or D atoms react with H2 with that for reactions 10.1 and 10.7 where common H atoms react with either H2 or D2 (compare Figs. 10.1a and b). In the first case, (kH,HH/kD,HH), there is a ZPE difference in the transition state but not the ground state consequently the high temperature KIE is inverse. In the second (kH,HH/kH,DD), however, there are zero point energy differences in both the transition and ground states. We expect the vibrational force constants to be smaller in the more loosely bound transition as compared to the ground state. The isotope effects scale with the force constant differences. Consequently RT[ln(kH,HH/kH,DD)] =... 

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... 

The interval scale makes use of both the order and the distance characteristics of numbers but does not use the origin property. The origin of an interval scale is arbitrary. For instance, the zero point on the scale of elevation is arbitrarily set at sea level. Other interval scales are Celsius and Fahrenheit temperature, date, latitude, and exam scores. The origin of latitude, for example, is the equator. Because this... 

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 ... 

Rankine Temperature Scale A temperature scale with the size of degree equal to that of the Fahrenheit scale and zero at absolute zero. Therefore 0°R = -459°F (-273,2°C) and the normal boiling point of water is 671.67°R. 

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

The KTTS depends upon an absolute zero and one fixed point through which a straight line is projected. Because they are not ideally linear, practicable interpolation thermometers require additional fixed points to describe their individual characteristics. Thus a suitable number of fixed points, ie, temperatures at which pure substances in nature can exist in two- or three-phase equilibrium, together with specification of an interpolation instrument and appropriate algorithms, define a temperature scale. The temperature values of the fixed points are assigned values based on adjustments of data obtained by thermodynamic measurements such as gas thermometry. 

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... 

Which temperature scale has its zero point as the point of zero atomic and molecular motion ... 

If you should decide to establish a new temperature scale based on the assumptions that the melting point of mercury (-38.9°C) is 0°M and the boiling point of mercury (356.9°C) is 100°M, what would be (a) the boiling point of water in degrees M, and (b) the temperature of absolute zero in degrees M ... 

Heat and temperature were poorly understood prior to Carnot s analysis of heat engines in 1824. The Carnot cycle became the conceptual foundation for the definition of temperature. This led to the somewhat later work of Lord Kelvin, who proposed the Kelvin scale based upon a consideration of the second law of thermodynamics. This leads to a temperature at which all the thermal motion of the atoms stops, By using this as the zero point or absolute zero and another reference point to determine the size of the degrees, a scale can be defined. The Comit e Consultative of the International Committee of Weights and Measures selected 273.16 K as the value lor the triple point for water. This set the ice-point at 273.15 K. 

For example for a two-phase (p = 2) water-ice (c = 1) system we have only one degree of freedom (/ = 1). Thus, we can change the temperature of water and still have coexisting ice, but only at one given pressure. This is the melting point (temperature) A (Fig. A.2) that lies on the coexistence line. If we move to point A we are in the water phase (p = 1) and according to (A.35) we now have two degrees of freedom (/ = 2), temperature and pressure. This triple point is where all three phases coexist (p = 3) it is uniquely defined (/ = 0). This temperature is the official zero of the Celsius scale. 

On the Celsius (or centigrade) scale, a temperature difference of 1°C is 1 K (exactly). The normal boiling point of water is 100°C, the normal freezing point 0°C, and absolute zero -273.15°C. On the Fahrenheit scale, a temperature difference of 1°F is 5/9 K (exactly). The boiling point and freezing point of water, and absolute zero are 212°F, 32°F and -459.67°F, respectively. Conversions from one temperature scale to another make use of the following equations ... 

Gabriel Fahrenheit in 1714 suggested for the zero point on his scale the lowest temperature then obtainable from a mixture of salts and ice, and for his 100° point he suggested the highest known normal animal temperature. Express these extremes in Celsius. 

Construct a temperature scale in which the freezing and boiling points of water are 100° and 400°, respectively, and the degree interval is a constant multiple of the Celsius degree interval. What is the absolute zero on this scale, and what is the melting point of sulfur (MP = 444.6°C) ... 

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