Temperature measurement Celsius scale

Three different scales are in common use for measurements of temperature the Celsius scale (expressed in degrees Celsius, or °C), the Fahrenheit scale (expressed in degrees Fahrenheit, or °F), and the Kelvin scale (expressed in kelvins, or K). The Fahrenheit scale is commonly used in daily life and in engineering work. The Celsius scale is used in scientific work and is coming into common usage in daily life in English-speaking countries. The Kelvin scale (also called the absolute scale) is the SI choice for temperature measurements, and it is widely used in scientific work. 

Temperature. Temperature maybe measured on an absolute or relative scale. The two most common relative scales are the Celsius and the Fahrenheit scales. The Celsius scale is defined as 0°C at the freezing point (triple point) of water and 100°C at the boihng point. The Fahrenheit scale is arbitrarily defined by assigning it a temperature of 32 degrees at the freezing point of water and 212°F at the boihng point of water (see Temperature measurements). 

Two scales used in die measuring of temperatures are Fahrenheit (F) and Celsius (C) (also known as centigrade). On the Fahrenheit scale, die freezing point of water is 32° F and die boiling point of water is 212° F. On die Celsius scale, 0° C is the freezing point of water and 100° C is die boiling point of water. 

We in the United States are used to thinking of temperature in Fahrenheit, but most of the rest of the world measures temperature in Celsius. On the Celsius scale water freezes at 0°C and boils at 100°C. Here are the equations needed to convert from Fahrenheit to Celsius and vice versa ... 

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). 

Some familiar temperatures measured on the Fahrenheit, Celsius, and Kelvin scales. 

Notice there is a key difference between Charles s Law and Boyle s Law. While the volume and pressure measurements in Boyle s Law can be measured in any units, as can the volume term in Charles s Law, we do not have this freedom with the temperature. As the relationship is formulated, the temperature must be expressed in kelvins.1 Recall the Kelvin scale starts at absolute zero, the coldest possible temperature. One kelvin is equal to 1°C, and the relationship between the Kelvin scale and the Celsius scale is ... 

We will assume that Charles measured temperature with a mercury thermometer calibrated for the centigrade (Celsius) scale. 

Despite imaginative suggestions by Isaac Newton and others, the Celsius centigrade system became the international scientific standard, prevailing for about two centuries. However, in 1954 the Celsius scale was replaced (at the 10th General Conference on Weights and Measures) by the. vmg/e-refcrence ideal gas temperature scale described in the text. 

Temperature is the measure of thermal energy (the total energy of all the atoms and molecules) of a system. The SI unit for temperature is Kelvin, but most scientific thermometers use the centigrade (Celsius) scale. However, most are more familiar with the Fahrenheit scale. Because many chemical calculations require Kelvin temperature, scientists frequently convert from degrees Celsius to Kelvin and from Kelvin to degrees Celsius. 

It was recognized by physicists a century ago that the concept tiuit wc call temperature is just the conmolecular motion. The idea suggested itself of a temperature so low that molecules < ease to move. This temperature was named the absolute zero. We usually measure temperature by the Fahrenheit scale (f.p. of water F, b,p. 212° F), or, in scientific work, by tlie Centigrade or Celsius scale (f.p. of air-saturated water at 1 atm pressure 0° C, boiling point of water... 

Temperature scales Hot and cold are qualitative terms. For quantitative descriptions of temperature, you need measuring devices such as thermometers. In a thermometer, a liquid expands when heated and contracts when cooled. The tube that contains the liquid is narrow so that small changes in temperature can be detected. Scientists use two temperature scales. The Celsius scale was devised by Anders Celsius, a Swedish astronomer. He used the temperatures at which water freezes and boils to establish his scale because these temperatures are easy to reproduce. He defined the freezing point as 0 and the boiling point as 100. Then he divided the distance between these points into 100 equal units, or degrees Celsius. 

Kelvin]—Although you will often measure temperature in Celsius degrees in your laboratory, Kelvin is the scale accepted by the International System of Measurements. 

Temperature Scientists often measure temperature using the Celsius scale. Pure water has a freezing point of 0°C and boiling point of 100°C. The unit of measurement is degrees Celsius. Two other scales often used are the Fahrenheit and Kelvin scales. 

In contrast, differences between any two values measured on the interval scale do have meaning. Temperature measured on the Celsius or Fahrenheit scale is an example of an interval scale. For example, the difference between 32°F and 64°F is the same as the difference between 64°F and 96°F. On the interval scale, a value of zero is not a true zero (meaning absence of heat) because a value of -1°F is colder still. We can perform... 

The Celsius scale is an interval scale for temperature measurement, since the arbitrary zero corresponds to the freezing point of water (0 °C). 

On the Celsius scale, the experimentally measured temperature of the steam point, which is the boiling point of water at a pressure of one atmosphere, is lOOWC. 

The International Practical Temperature Scale consists of a number of equilibrium states which have been assigned temperatures on the Celsius scale, to facilitate the measurement of temperatures everywhere. Since the number of degrees between the triple point of water and any other equilibrium state, such as the freezing point of molten zinc, is a matter of experimental determination, the temperature values assigned to the chosen fixed points are changed from time to time as techniques improve. 

Another temperature scale, used in Canada and Europe and in the physical and life sciences in most countries, is the Celsius scale. In keeping with the metric system, which is based on powers of 10, the freezing and boiling points of water on the Celsius scale are assigned as 0 °C and 100. °C, respectively. On both the Fahrenheit and the Celsius scales, the unit of temperature is called a degree, and the symbol for it is followed by the capital letter representing the scale on which the units are measured °C or °F. 

Three systems for measuring temperature are widely used the Celsius scale, the Kelvin scale, and the Fahrenheit scale. The first two temperature systems are used in the physical sciences, and the third is used in many of the engineering sciences. Our purpose here is to define the three temperature scales and show how conversions from one scale to another can be performed. Although these conversions can be carried out routinely on most calculators, we will consider the process in some detail here to illustrate methods of problem solving. 

Vo is the initial volume of a certain amount of gas at, for example, a temperature of 0 °C (ice point), and is its temperature on the Celsius scale. A graphic or analytic extrapolation of the isobars F(5) (Fig. 10.2) leads to an important conclusion AU the linear functions F(5) belonging to different constant pressures, will intersect with the temperature axis at about 3= —267 °C (actually at 273.15 °C, as later measurements have shown), independent of the type of gas and amount of substance. The experiments carried out by Charles and Gay-Lussac were therefore a further indication of the existence of an absolute zero point of temperature. This had already been postulated in 1706 by Guillaume Amonton. It seemed, therefore, reasonable to introduce a new temperamre scale and to measure temperature from this point because volume is never negative. This is how we arrive at the so-called absolute temperature scale. We were already introduced to this scale in Sect. 3.8 (but there we did not use the ice point but the more convenient triple point of water to fix the scale). Further, it also becomes clear that Eq. (10.2) is an example of a... 

SECTION 1.4 Measurements in chemistry are made using the metric system. Special emphasis is placed on SI units, which are based on the meter, the kilogram, and the second as the basic units of length, mass, and time, respectively. SI units use prefixes to indicate fractions or multiples of base units. The SI temperature scale is the Kelvin scale, although the Celsius scale is frequently used as well. Density is an important property that equals mass divided by volume. 

In practice, temperature is usually measured in empirical scales that were originally developed before the precise notion of temperature was clear. The two most widely used are the Celsius scale and the Fahrenheit. They are related to each other and to the absolute scales as follows ... 

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