# Entropy and second law of thermodynamics examples pdf

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## System or Surroundings

### What is the Second Law of Thermodynamics?

In order to avoid confusion, scientists discuss thermodynamic values in reference to a system and its surroundings. Everything that is not a part of the system constitutes its surroundings. The system and surroundings are separated by a boundary. For example, if the system is one mole of a gas in a container, then the boundary is simply the inner wall of the container itself. Everything outside of the boundary is considered the surroundings, which would include the container itself.

Thermodynamics is the study of heat, energy, and motion. Think dynamite-a powerful explosion of energy! The three laws of thermodynamics help us understand how heat, energy, and motion work within the universe. The 1st law of thermodynamics says energy cannot be created or destroyed. This law helps us understand that energy never disappears or goes away, it only gets moved around, or used in different ways. Imagine having a collection of blocks. You could use your blocks to build a really nice tower!

There is yet another way of expressing the second law of thermodynamics. This version relates to a concept called entropy. By examining it, we shall see that the directions associated with the second law—heat transfer from hot to cold, for example—are related to the tendency in nature for systems to become disordered and for less energy to be available for use as work. The entropy of a system can in fact be shown to be a measure of its disorder and of the unavailability of energy to do work. Recall that the simple definition of energy is the ability to do work. Entropy is a measure of how much energy is not available to do work. Although all forms of energy are interconvertible, and all can be used to do work, it is not always possible, even in principle, to convert the entire available energy into work.

Figure 1. The ice in this drink is slowly melting. Eventually the liquid will reach thermal equilibrium, as predicted by the second law of thermodynamics. There is yet another way of expressing the second law of thermodynamics. This version relates to a concept called entropy. By examining it, we shall see that the directions associated with the second law—heat transfer from hot to cold, for example—are related to the tendency in nature for systems to become disordered and for less energy to be available for use as work. The entropy of a system can in fact be shown to be a measure of its disorder and of the unavailability of energy to do work.

### The Second Law: Thermodynamic Temperature and Entropy

In this chapter we consider a more abstract approach to heat engine, refrigerator and heat pump cycles, in an attempt to determine if they are feasible, and to obtain the limiting maximum performance available for these cycles. The concept of mechanical and thermal reversibility is central to the analysis, leading to the ideal Carnot cycles. Refer to Wikipedia: Sadi Carnot a French physicist, mathematician and engineer who gave the first successful account of heat engines, the Carnot cycle, and laid the foundations of the second law of thermodynamics.

Thermodynamics , science of the relationship between heat , work , temperature , and energy. In broad terms, thermodynamics deals with the transfer of energy from one place to another and from one form to another. The key concept is that heat is a form of energy corresponding to a definite amount of mechanical work. Thermodynamics is the study of the relations between heat, work, temperature, and energy. The laws of thermodynamics describe how the energy in a system changes and whether the system can perform useful work on its surroundings.

Entropy Physics. This tells us that the right hand box of molecules happened. The entropy sink owing to this heat sink is then just equal to the heat sink divided by the outflow temperature: The main irreversible entropy source in the control volume is assumed to arise from dissipation of the kinetic energy of the wind, and this is assumed to occur mostly in the boundary layer, at a temperature of. Most likely you have knowledge that, people have see numerous.

The laws of thermodynamics describe the relationships between thermal energy, or heat, and other forms of energy, and how energy affects matter.

### System or Surroundings

The second law of thermodynamics establishes the concept of entropy as a physical property of a thermodynamic system. Entropy predicts the direction of spontaneous processes, and determines whether they are irreversible or impossible, despite obeying the requirement of conservation of energy , which is established in the first law of thermodynamics. The second law may be formulated by the observation that the entropy of isolated systems left to spontaneous evolution cannot decrease, as they always arrive at a state of thermodynamic equilibrium , where the entropy is highest. If all processes in the system are reversible , the entropy is constant. An increase in entropy accounts for the irreversibility of natural processes, often referred to in the concept of the arrow of time. Historically, the second law was an empirical finding that was accepted as an axiom of thermodynamic theory.

The laws of thermodynamics define a group of physical quantities, such as temperature , energy , and entropy , that characterize thermodynamic systems in thermodynamic equilibrium. The laws also use various parameters for thermodynamic processes , such as thermodynamic work and heat , and establish relationships between them. They state empirical facts that form a basis of precluding the possibility of certain phenomena, such as perpetual motion. In addition to their use in thermodynamics , they are important fundamental laws of physics in general, and are applicable in other natural sciences. Traditionally, thermodynamics has recognized three fundamental laws, simply named by an ordinal identification, the first law, the second law, and the third law. The zeroth law of thermodynamics defines thermal equilibrium and forms a basis for the definition of temperature: If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other. The first law of thermodynamics states that, when energy passes into or out of a system as work , heat , or matter , the system's internal energy changes in accord with the law of conservation of energy.

The learning objectives in this section will help your students master the following standards:. Recall earlier discussions on engine efficiency.

#### Heat Death of the Universe: An Overdose of Entropy

Because work is obtained from ordered molecular motion , the amount of entropy is also a measure of the molecular disorder, or randomness, of a system. The concept of entropy provides deep insight into the direction of spontaneous change for many everyday phenomena. Its introduction by the German physicist Rudolf Clausius in is a highlight of 19th-century physics. The idea of entropy provides a mathematical way to encode the intuitive notion of which processes are impossible, even though they would not violate the fundamental law of conservation of energy. For example, a block of ice placed on a hot stove surely melts, while the stove grows cooler.

According to Sommerfeld, the well known Clausius and Kelvin statements of the second law of thermodynamics comprises two parts. The first part includes the Carnot principle that all Carnot engines operating between the same temperatures have the same efficiency. The second part contains the law of increase in entropy. Usually, the two parts are understood as a logical consequence of these statements, including the Carnot principle. Here, we argue that this principle need not be a derived law and may be considered as a fundamental law, without the need of demonstration. To this end we analyze the roots of the second law, which are contained in the memoir of Carnot on the production of work by heat, and its emergence in the papers of Clausius on heat. The second law of thermodynamics as conceived by Clausius [1] and Kelvin [2] can be understood as having two parts, which Sommerfeld [3] called the first and second parts of the second law.

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