Degree of hotness

Heat q and temperature T are related but distinct concepts. Temperature T can be identified as degree of hotness (Section 2.3), whereas heat q is a quantity of thermal energy. The same quantity of heat might be stored under different conditions, for example, as high-temperature heat or low-temperature heat in heat reservoirs of different temperature. Further aspects of how the temperature of a heat quantity affects its usefulness (e.g., for conversion to useful work) will be discussed in Chapter 4. 

The concept of temperature can be defined operationally that is, in terms of a set of operations or conditions that define the concept. To define a temperature scale operationally we need (1) one particular pure or defined substance (2) a specific property of that substance that changes with a naive sense of degree of hotness (i.e., temperature) (3) an equation relating temperature to the specific property (4) a sufficient number of fixed points (defined as reproducible temperatures) to evaluate the constants in the equation in (3) and (5) the assignment of numerical values to the fixed points. Historically, many different choices have been made with respect to the five conditions listed above, and this, of course, has resulted in many temperature scales. 

Temperahire is commonly measured with liquid-in-glass thermometers, wherein the hquid expands when heated. Thus a uniform hibe, partially filled with mercury, alcohol, or some otherfluid, can indicate degree of "hotness" simply by the length of tire fluid colunm. However, numerical values are assigned to the various degrees of hotness by arbitrary definition. 

Temperature is a measure of the degree of hotness of an object. Objects at various degrees of hotness can be assigned numbers, one to each object, in order of increasing hotness. This sequence of numbers represents temperature. Two objects in thermal contact eventually reach a state of the same hotness. They are at thermal equilibrium and at the same temperature. Two objects that are separately at thermal equilibrium with a third object are also at the same temperature. 

In the sixteenth century, there was a revival of interest in the mechanical devices of the Greeks. Although it is not known with certainty who at that time first conceived the idea of measuring temperature or degrees of hotness, Galileo Galilei is usually credited with the invention of the first thermometer. His writings contain only one reference to the instrument, which he likely did not consider of any importance. His friends and students, however, fortunately recorded a description of the instrument that he invented shortly after 1592. 

Temperature is the degree of "hotness" of an object. This may not sound like a very "scientific" definition, and, in a sense, it is not. We know intuitively the difference between a "hot" and a "cold" object, but developing a precise definition to explain this is not easy. We may think of the temperature of an object as a measure of the amount of heat in the object. However, this is not strictly true. An object increases in temperature because its heat content has increased and vice versa however, the relationship between heat content and temperature depends on the composition of the material. 

Temperature is the degree of "hotness" of an object. Many substances, such as liquid mercury, expand as their... 

If a gas becomes hotter, the pressure which it exerts increases. In the first instance hotness is gauged simply by sensation. Since p is proportional to mu, that is to the mean kinetic energy of the molecules, the hotness appears to be a function of the invisible translational motion. So rational does this interpretation of the origin of the sensation seem that it becomes expedient to introduce a scale of hotness and to define the degree of hotness, or temperature, as proportional to the pressure which a gas having that degree would exert. For a standard scale the gas must obey Boyle s law. This so-called perfect gas scale is simple theoretically and convenient practically, since the deviations of actual gases from the law are easily corrected for by extrapolation to low pressures. 

Definition The degree of hotness or coldness. [41] A measure of the average (inordinate) kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale. 

Turning to the other meanings of the word heat listed in most dictionaries, one finds that a degree of hotness is impUed. This indicates that heat is stUl confused with its intensive parameter temperature. The example the heat of this room is unbearable is expressed correctly by saying the temperature of this room is unbearable. The improper use of heat in this case becomes clear on recognizing that,... 

The third meaning of heat involves the quantity of heat. This reveals that heat actually is an extensive quantity, meaning that it doubles if one doubles the amount of material talked about. Doubling the size of an object will take twice the amount of heat to reach the same degree of hotness (temperature). 

Temperature may be defined simply as the degree of hotness or coldness of a material or of the atmosphere. Heat is a form of energy and temperature is a measure of the level of this energy. 

Energy transfers from a hot body to a cold body in a spontaneous manner when brought in contact with each other. The degree of hotness or coldness is defined by a quantity called temperature. The units of temperature, of a system are °C, Celsius, or F, Fahrenheit. The conversion of Fahrenheit to Celsius can be given by... 

We consider two bodies, each of them a homogeneous phase in a state of internal equilibrium, which are in contact through a non-adiabatic wall. The thermodynamic state of each body may be completely specified by means of two variables only, and these may conveniently be chosen as the volume per unit mass and the pressure. These variables will determine the property called hotness , together with all other properties. Let the variables be p and v for the one body and P and V for the other. When they are brought into contact in this way, at initially different degrees of hotness, there is a slow change in the values of the pressures and volumes until the state of thermal... 

This question need not be pursued any further because we shall shortly obtain a definition of a thermodynamic temperature having the important properties (a) it is independent of any particular substance (6) the temperatures are always positive numbers and increase with increasing degrees of hotness. This scale may be shown to be identical with the scale (6) above. 

Temperature and thermometry are of fundamental importance in thermodynamics. Unlike the other physical quantities discussed in this chapter, temperature does not have a single unique definition. The chosen definition, whatever it may be, requires a temperature scale described by an operational method of measuring temperature values. For the scale to be useful, the values should increase monotonically with the increase of what we experience physiologically as the degree of hotness. We can define a satisfactory scale with any measuring method that satisfies this requirement. The values on a particular temperature scale correspond to a particular physical quantity and a particular temperature unit. 

The most insightful use of the thermometer was made by Joseph Black (1728-1799), a professor of medicine and chemistry at Glasgow. Black drew a clear distinction between temperature or degree of hotness, and the quantity of heat. His experiments using the newly developed thermometers established the fundamental fact that, in thermal equilibrium, the temperatures of all the... 

---