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Chapter 1: Problem 3

What is the caloric theory? When and why was it abandoned?

Short Answer

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Answer: The caloric theory was abandoned in the mid-19th century due to several factors, including experimental evidence from Count Rumford and James Prescott Joule, the discovery of the first law of thermodynamics, and advances in kinetic theory. These scientific discoveries and advances collectively showed that heat is a form of energy related to the motion of particles within a substance, and not an invisible fluid substance as previously believed. This new understanding of heat replaced the outdated caloric theory.

Step by step solution

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1. Understanding the Caloric Theory

Caloric theory is a historical theory in thermodynamics, which stated that heat was a self-repellent fluid known as "caloric." This invisible fluid was believed to flow from hotter objects to colder ones, creating a sensation of warmth or coldness during the flow. The caloric theory was prominent from the 18th century up until the mid-19th century.
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2. When was the Caloric Theory Abandoned?

The caloric theory was mainly abandoned in the mid-19th century. This transition took place as new scientific discoveries provided strong evidence against the caloric theory, leading to the development of a new understanding of heat.
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3. Reasons for Abandonment

The caloric theory was abandoned due to several factors, including: - Experimental evidence from Count Rumford and James Prescott Joule: In the late 18th century, Count Rumford observed that heat was produced during the mechanical process of boring cannons. This observation went against the caloric theory, which suggested that heat was a fluid substance, rather than a form of energy. Likewise, James Prescott Joule's experiments in the mid-19th century demonstrated that heat could be generated through work, supporting the idea that heat was a form of energy rather than a fluid substance. - Discovery of the first law of thermodynamics: This law established the relationship between heat, work, and energy, indicating that heat was a form of energy and not an invisible substance. The discovery of this law further put the caloric theory into question and contributed to its abandonment. - Advances in kinetic theory: The development of kinetic theory revealed that heat could be understood as the result of the motion of molecules within a substance. This understanding provided an additional explanation for the transfer and generation of heat that contradicted the idea of caloric as a fluid substance. As a result of these scientific discoveries and advances, the caloric theory was replaced by the understanding that heat is a form of energy that could be converted into other forms and is related to the motion of particles within a substance.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Thermodynamics
Thermodynamics is a branch of physics that deals with the relationships between heat, work, and energy. As a fundamental science, it defines macroscopic variables, such as temperature, energy, and entropy, and forms the basis of understanding how energy transforms and transfers between systems. It operates on the principle that energy cannot be created or destroyed, only changed in form, a concept vital for numerous scientific and engineering applications, from engines to ecosystems.

At the core of thermodynamics is the intuitive notion that there's a measurable quantity called temperature, which provides an axis to gauge the direction of heat flow naturally from hot to cold. This reflects everyday experiences, such as feeling the warmth of the sun or the coolness of a breeze. Thermodynamics gives us formalism through laws to predict how heat exchange leads to changes in physical properties of materials and systems.
History of Heat Transfer

The Shift from Caloric Theory to Energy-based Understanding

Exploring the history of heat transfer uncovers a significant shift in scientific perspective during the 18th and 19th centuries. Initially, the caloric theory proposed that an invisible fluid, caloric, was responsible for heat transfer, embodying a materialistic view of heat. This viewpoint held sway in scientific circles until a series of experiments illustrated the flaws in this theory. The observations by Count Rumford and later quantitative experiments by James Prescott Joule set the stage for a radical paradigm shift. They showed that heat could be related to mechanical work, dispelling the idea of a heat 'substance.'

With these findings, the concept of heat evolved to align with the broader, more robust framework of energy which led to the acceptance that heat was a form of energy transfer. This transition was not abrupt but resulted from cumulative evidence that contradicted the caloric theory and augmented by theoretical developments in areas such as the kinetic theory of gases.
First Law of Thermodynamics
The first law of thermodynamics, often considered the principle for the conservation of energy, states that the energy within a closed system must remain constant. It could be summarized by the equation \[\Delta E = Q - W\], where \(\Delta E\) represents the change in internal energy of the system, \(Q\) is the heat added to the system, and \(W\) is the work done by the system. This scientific milestone carried immense implications for our understanding of heat transfer as it emphatically severed the ties with the discredited caloric theory.

Put simply, the law affirms that energy can be exchanged between a system and its surroundings in the form of heat or work, and it is the very interplay of these two forms that sustains processes in physics, chemistry, biology, and engineering. The discovery and acceptance of the first law signified a leap forward in physics and laid the foundation for the second and third laws, providing a comprehensive framework for the study of energy interactions.

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Most popular questions from this chapter

Two surfaces, one highly polished and the other heavily oxidized, are found to be emitting the same amount of energy per unit area. The highly polished surface has an emissivity of \(0.1\) at \(1070^{\circ} \mathrm{C}\), while the emissivity of the heavily oxidized surface is \(0.78\). Determine the temperature of the heavily oxidized surface.

A 2.1-m-long, 0.2-cm-diameter electrical wire extends across a room that is maintained at \(20^{\circ} \mathrm{C}\). Heat is generated in the wire as a result of resistance heating, and the surface temperature of the wire is measured to be \(180^{\circ} \mathrm{C}\) in steady operation. Also, the voltage drop and electric current through the wire are measured to be \(110 \mathrm{~V}\) and \(3 \mathrm{~A}\), respectively. Disregarding any heat transfer by radiation, determine the convection heat transfer coefficient for heat transfer between the outer surface of the wire and the air in the room. Answer: \(156 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}\)

A flat-plate solar collector is used to heat water by having water flow through tubes attached at the back of the thin solar absorber plate. The absorber plate has a surface area of \(2 \mathrm{~m}^{2}\) with emissivity and absorptivity of \(0.9\). The surface temperature of the absorber is \(35^{\circ} \mathrm{C}\), and solar radiation is incident on the absorber at \(500 \mathrm{~W} / \mathrm{m}^{2}\) with a surrounding temperature of \(0^{\circ} \mathrm{C}\). Convection heat transfer coefficient at the absorber surface is \(5 \mathrm{~W} / \mathrm{m}^{2} \cdot \mathrm{K}\), while the ambient temperature is \(25^{\circ} \mathrm{C}\). Net heat rate absorbed by the solar collector heats the water from an inlet temperature \(\left(T_{\text {in }}\right)\) to an outlet temperature \(\left(T_{\text {out }}\right)\). If the water flow rate is \(5 \mathrm{~g} / \mathrm{s}\) with a specific heat of \(4.2 \mathrm{~kJ} / \mathrm{kg} \cdot \mathrm{K}\), determine the temperature rise of the water.

Consider a person whose exposed surface area is \(1.7 \mathrm{~m}^{2}\), emissivity is \(0.5\), and surface temperature is \(32^{\circ} \mathrm{C}\). Determine the rate of heat loss from that person by radiation in a large room having walls at a temperature of \((a) 300 \mathrm{~K}\) and (b) \(280 \mathrm{~K}\). Answers: (a) \(26.7 \mathrm{~W}\), (b) \(121 \mathrm{~W}\)

A hollow spherical iron container with outer diameter \(20 \mathrm{~cm}\) and thickness \(0.2 \mathrm{~cm}\) is filled with iced water at \(0^{\circ} \mathrm{C}\). If the outer surface temperature is \(5^{\circ} \mathrm{C}\), determine the approximate rate of heat loss from the sphere, in \(\mathrm{kW}\), and the rate at which ice melts in the container. The heat of fusion of water is \(333.7 \mathrm{~kJ} / \mathrm{kg}\).
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