What is thermodynamics the study of

When a high temperature body is brought into contact with a low temperature body, the temperatures equilibrate: there is heat flow from higher to lower temperature, like water flowing downhill, until the temperatures of the bodies are equivalent. The high temperature body loses thermal energy, and the low temperature body acquires this same amount of thermal energy. The system is then said to be at thermal equilibrium.

An illustration of thermal equilibrium : The can of cola and ice cube start at different temperatures. When they come into contact, heat is transferred from the cola can to the ice cube until both bodies reach thermal equilibrium. Work is the transfer of energy by any process other than heat. Like heat, the unit measurement for work is joules J. There are many forms of work, including but not limited to mechanical, electrical, and gravitational work.

For our purposes, we are concerned with P-V work, which is the work done in an enclosed chemical system. In this type of system, work is defined as the change in the volume V in liters within the system multiplied by a pressure P.

Assuming the system is at constant pressure, this equates to the following:. Most often, we are interested in the work done by expanding gases. Assuming the gases are ideal, we can apply the ideal gas law to the above equation to get the following:. Heat and work are related. Work can be completely converted into heat, but the reverse is not true: heat energy cannot be wholly transformed into work energy. This means that the total energy within a system is affected by the sum of two possible energy transfers: heat and work.

Privacy Policy. Skip to main content. Search for:. Introduction to Thermodynamics The First Law of Thermodynamics The first law of thermodynamics states that energy can be transferred or transformed, but cannot be created or destroyed. Learning Objectives Describe the first law of thermodynamics. All matter emits and absorbs some EM radiation, the net amount of which determines whether this causes a loss or gain in heat. The cycle exploits the relationships among pressure, volume and temperature of gasses and how an input of energy can change form and do work outside the system.

Compressing a gas increases its temperature so it becomes hotter than its environment. Heat can then be removed from the hot gas using a heat exchanger. Then, allowing it to expand causes it to cool.

This is the basic principle behind heat pumps used for heating, air conditioning and refrigeration. Conversely, heating a gas increases its pressure, causing it to expand.

The expansive pressure can then be used to drive a piston, thus converting heat energy into kinetic energy. This is the basic principle behind heat engines.

All thermodynamic systems generate waste heat. This waste results in an increase in entropy, which for a closed system is "a quantitative measure of the amount of thermal energy not available to do work," according to the American Heritage Dictionary. Entropy in any closed system always increases; it never decreases. Additionally, moving parts produce waste heat due to friction, and radiative heat inevitably leaks from the system. This makes so-called perpetual motion machines impossible.

Siabal Mitra, a professor of physics at Missouri State University, explains, "You cannot build an engine that is percent efficient, which means you cannot build a perpetual motion machine.

However, there are a lot of folks out there who still don't believe it, and there are people who are still trying to build perpetual motion machines. Entropy is also defined as "a measure of the disorder or randomness in a closed system," which also inexorably increases.

You can mix hot and cold water, but because a large cup of warm water is more disordered than two smaller cups containing hot and cold water, you can never separate it back into hot and cold without adding energy to the system.

While some processes appear to be completely reversible, in practice, none actually are. Entropy, therefore, provides us with an arrow of time: forward is the direction of increasing entropy. The fundamental principles of thermodynamics were originally expressed in three laws. Later, it was determined that a more fundamental law had been neglected, apparently because it had seemed so obvious that it did not need to be stated explicitly. To form a complete set of rules, scientists decided this most fundamental law needed to be included.

The problem, though, was that the first three laws had already been established and were well known by their assigned numbers. When faced with the prospect of renumbering the existing laws, which would cause considerable confusion, or placing the pre-eminent law at the end of the list, which would make no logical sense, a British physicist, Ralph H.

The Zeroth Law states that if two bodies are in thermal equilibrium with some third body, then they are also in equilibrium with each other. This establishes temperature as a fundamental and measurable property of matter. The First Law states that the total increase in the energy of a system is equal to the increase in thermal energy plus the work done on the system.

When heat is transformed into any other form of energy, or when other forms of energy are transformed into heat, the total amount of energy heat plus other forms in the system is constant. The total entropy measurement of internal energy of any isolated thermodynamic system tends to increase over time, approaching a maximum value.

As a system asymptotically approaches absolute zero of temperature, all processes virtually cease and the entropy of the system asymptotically approaches a minimum value. In sync with the Third Law of Thermodynamics, in addition to, being composed of all the core tenets of thermodynamics, the Thermodynamic Scale of Temperature also known as the absolute or Kelvin scale is considered to be the absolute measure of temperature.

It is an absolute scale not just because it is used to measure temperature or heat, but also that it measures the fundamental property underlying temperature, that of the null or zero point on the thermodynamic temperature scale. By definition, absolute zero is the lowest possible temperature where nothing can be colder and no more heat energy can be extracted from a substance.

An important concept in thermodynamics is the system. A system is the region of the universe which is considered to be undergoing study. Isolated Systems. Where matter and energy do not cross the boundary.

In isolated systems, overall internal differences in the system eventually even out; pressures, temperatures, and density differences tend to balance out. When a system possesses areas which are nearly all equal, it is considered to be in a state of thermodynamic equilibrium.

In thermodynamic equilibrium, by definition, a system's properties do not change over time. Basically, systems in equilibrium are much simpler and easier to understand than systems which are not in equilibrium.

Most times, when analyzing a thermodynamic process, it can be assumed that each intermediary state is at equilibrium. This also helps to simplify the measurement of the process. The central concept of thermodynamics revolves around the idea of energy, hence, the ability to do work. As explained by the first law, the energy level of the entire system, as well as its surroundings, are conserved. The energy may be transferred to a body through such means as: heating, compression, or by the addition of more matter.

It may be extracted by: cooling, expansion, or the extraction of matter. To provide a means for comparison, in mechanics, energy transfers result from forces that cause displacement. Thereby, the product of the two equals the total amount of energy that is being transferred. In a similar sense, thermodynamic systems entail transferring energy that is produced by a generalized force which causes a generalized displacement.

Thus, the product of the two equals the total amount of energy that is being transferred. Under a specified set of conditions, when a system is at equilibrium, it is said to exist in a definite state. The state of the system can be described by both intensive and extensive variables. In turn, the properties of the system can be described by an equation of state that specifies the nature of the relationship that exists between the variables.

The definition for a thermodynamic process is the energy-infused transformation of a thermodynamic system whereby it moves from an introductory state to a final one. An isobaric process.

Takes place at a constant pressure.