Heat, temperature, and kinetic theory of matter

Physical Science: Heat

It is reasonable to suggest that just about everyone has felt the warmth of the sun or warmed themselves by a fireside, but many people may not understand the source of the energy they are feeling, particularly at the molecular level. Without heat, though, humankind would soon cease to exist and the universe would quickly collapse into an absolute zero nothingness. To gain some further insights into this essential source of life, this paper provides a review of the relevant literature to define heat and temperature, the relationship between them, and how they are different. A discussion concerning the various properties of a substance that determine its heat capacity is followed by a description of some of the various sources of heat. Finally, an analysis concerning how the study of heat relates to the kinetic theory of matter is followed by a summary of the research and important findings in the conclusion.

Review and Analysis

What is heat?

Interestingly, heat is not static energy but rather by definition is moving from a hotter object to a cooler object. For instance, according to Nave (2005). "Heat may be defined as energy in transit from a high temperature object to a lower temperature object" (para. 1). Because heat is always in transit, it is also differentiated from heat produced from an object's internal energy. In this regard, Nave adds that, "An object does not possess 'heat'; the appropriate term for the microscopic energy in an object is internal energy. The internal energy may be increased by transferring energy to the object from a higher temperature (hotter) object - this is properly called heating" (Nave, 2005, para. 2).

What is temperature?

Temperature is a measure of hotness, or how much heat an object receives from another object (Cavendish, 2003).

What is the relationship between heat and temperature?

Heat and temperature both involve the transmission of energy (Cavendish, 2003).

How are they different?

Although both temperature and heat involve the transmission of energy, they are different in that heat is less related to the concept of hotness than temperature. For instance, Cavendish reports that, "Temperature is clearly related to heat, but is even more directly related to the notion of hotness. No net transfer of heat occurs when two bodies at the same temperature are in contact, but when a body comes into contact with another at a lower temperature, heat will be transferred to the cooler body until the two reach the same temperature or until they are separated" (2003, p. 2414). Likewise, Thewlis et al. report that, "Heat is a form of energy, associated with the motion of individual atoms or molecules of a body. It is to be distinguished from temperature, which is a measure of the degree of hotness" (1992, p. 592).

Another interesting feature concerning the difference between temperature and heat is that it is possible for a cooler body to actually contain more heat than a hotter body, and despite this difference, the energy flow will continue from hotter to cooler bodies while they are in physical contact (Cavendish, 2003). The term "heat capacity" is used to define the amount of heat that is needed to increase the temperature of a given body by one degree Celsius (Cavendish, 2003).

What are the various properties of a substance that determine its heat capacity?

The heat capacity of an object is the combination of several factors, including:

1. How much mass it possesses;

2. What is in the mass; and,

3. Its physical state (Cavendish, 2003).

For example, according to Cavendish, "The heat capacity of a body depends upon its mass (the amount of matter present) as well as its compositional and physical state. Hence, a cold body that has a greater heat capacity may hold more heat than a hot body that has a lower heat capacity" (2003, p. 2414).

What are the various sources of heat?

Far and away, the main source of heat for earthlings at least is the Sun, but chemical and other nuclear reactions can also produce heat (Cavendish, 2003), as well as physical friction and high pressure which also produce heat (Thewlis, Glass & Hughes, 1992).

How does the study of heat relate to the kinetic theory of matter?

Like temperature and heat, the study of heat and the kinetic theory of matter are also inextricably interrelated because they both concern the manner in which energy is transmitted from one object to another. For instance, according to Brown (2001), "The kinetic theory of matter says that heat is the random motion of tiny bits of matter which obey the laws of mechanics" (p. 75). Irrespective of its reliance on the known laws of physics in this area, the kinetic theory of matter remains just that: a theory. In this regard, Brown emphasizes that, "The theory explains a lot, but the evidence does not pick out this theory uniquely. Speaking logically, there are other possibilities, such as a theory that says heat is a kind of fluid. The evidence that is available narrows the possibilities considerably, but not to a single choice" (2001, p. 75). Nevertheless, O'Callaghan (2008) characterizes the kinetic theory of matter when applied to the Ideal Gas Law as being one of the "discoveries of underlying unity that revolutionized modern science in the nineteenth and early twentieth centuries" (p. 4).