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Thermodynamics - Definition, Properties, Process, FAQs

Thermodynamics - Definition, Properties, Process, FAQs

Team Careers360Updated on 02 Jul 2025, 04:42 PM IST

Thermodynamics is associated with the ideas of heat and temperature, as well as the exchange of heat and other forms of energy. The four principles of thermodynamics govern the behaviour of these quantities, which provide a quantitative description using quantifiable macroscopic physical characteristics also described by statistical mechanics in term of microscopic element..

This Story also Contains

  1. What is the definition of thermodynamics?
  2. Properties of Thermodynamics
  3. Process of Thermodynamics
Thermodynamics - Definition, Properties, Process, FAQs
Thermodynamics

The four rules of thermodynamics, which provide an axiomatic basis, are used to describe any thermodynamic system. The first law states that energy can be transferred across physical systems in the form of heat or work. The second law establishes the existence of a quantity known as entropy, which explains the thermodynamic direction in which a system might modifies as well as quantifies order of system, and work which can be extracted.

What is the definition of thermodynamics?

Thermodynamics Definition: Thermodynamics is a discipline of physics that studies heat, work, and temperature, as well as their relationships with energy, radiation, and matter's physical properties.

Different Thermodynamics Branches

The following are the four branches of thermodynamics:

  • Classical Thermodynamics.
  • Statistical Thermodynamics.
  • Chemical Thermodynamics.
  • Equilibrium Thermodynamics.

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Commonly Asked Questions

Q: What is thermodynamics?
A:
Thermodynamics is the branch of physics that deals with heat, work, temperature, and their relation to energy. It describes how thermal energy is converted to and from other forms of energy and how it affects matter.
Q: What is a heat engine and how does it work?
A:
A heat engine is a device that converts thermal energy into mechanical work. It operates by transferring heat from a high-temperature reservoir to a low-temperature reservoir, using some of that energy to perform work in the process. Examples include steam engines and internal combustion engines.
Q: What is specific heat capacity and how does it affect heating and cooling?
A:
Specific heat capacity is the amount of heat energy required to raise the temperature of one unit mass of a substance by one degree. Substances with higher specific heat capacities require more energy to heat up and take longer to cool down, affecting how they interact thermally with their environment.
Q: How does the concept of free energy relate to spontaneous processes?
A:
Free energy is a measure of the energy available to do useful work in a system. A spontaneous process is one that occurs without external input and is associated with a decrease in free energy. The concept of free energy helps predict the direction and extent of chemical reactions and physical changes.
Q: How does the concept of exergy differ from energy?
A:
Exergy is the maximum useful work that can be extracted from a system as it reaches equilibrium with its surroundings. Unlike energy, which is conserved, exergy can be destroyed through irreversible processes. This concept is useful for analyzing the efficiency of energy conversion processes.

Properties of Thermodynamics

Thermodynamic properties are defined as characteristics of a system that can be used to specify the state of the system. Thermodynamic properties can be broad or narrow.

  1. Intensive properties are those that are independent of the amount of substance present. The qualities of temperature and pressure are both significant.
  2. The value of extensive characteristics is proportional to the system's mass. Volume, energy, and enthalpy are all important properties to consider.

Zeroth law of thermodynamics.

Two thermodynamic systems in thermal equilibrium with a third system are in thermal equilibrium with each other independently, according to the zeroth law of thermodynamics.

Thermodynamics' First Law

Energy cannot be created or destroyed, according to the first law of thermodynamics, yet it can be converted from one form to another.

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Thermodynamics' First Law: Examples

The first law of thermodynamics may seem abstract, but by looking at a few examples, we may have a better understanding of it.

Equation: ΔU = Q − W. Here ΔU is the change in internal energy U of the system.

Example: Light bulbs transform electrical energy into light energy (radiant energy).

Thermodynamics' Second Law

The second rule of thermodynamics states that entropy constantly increases in an isolated system. Any isolated system will advance toward thermal equilibrium, or maximum entropy, on its own. The universe's entropy is always increasing and never decreasing. Many people take this statement for granted, but it has a significant influence and consequence.

Thermodynamics' Second Law: Examples

If a room is not cleaned or tidied, it will become more cluttered and disordered over time. The entropy in the room drops when it is cleaned, but the effort to clean it has led in a rise in entropy outside the room that is more than the entropy lost.

Thermodynamics' Third Law.

When the temperature approaches absolute zero, the entropy of a system approaches a constant value, according to the third rule of thermodynamics.

To learn the third law of thermodynamics step by step, let's use steam as an example:

  1. Its molecules are free to move about and have high entropy.
  2. When the temperature is reduced to 100 °C, steam is transformed to water, which restricts the movement of molecules, lowering the entropy of water.
  3. When water is chilled below 0 degrees Celsius, it solidifies as ice. The mobility of molecules is further constrained in this condition, and the system's entropy decreases.
  4. The movement of the molecules in the ice is further constrained when the temperature of the substance drops and the entropy of the substance decreases.
  5. The entropy should be zero when the ice is cooled to absolute zero. In actuality, cooling any substance to zero is impossible.

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Commonly Asked Questions

Q: What is the zeroth law of thermodynamics and why is it important?
A:
The zeroth law of thermodynamics states that if two systems are in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This law is important because it establishes the concept of temperature and allows us to use thermometers to measure it.
Q: Why is absolute zero temperature unattainable?
A:
Absolute zero (0 Kelvin or -273.15°C) is unattainable because it would require removing all thermal energy from a system. The third law of thermodynamics implies that as we approach absolute zero, it becomes increasingly difficult to remove more energy, making it impossible to reach exactly 0 K.
Q: What is the difference between an open, closed, and isolated system in thermodynamics?
A:
An open system can exchange both matter and energy with its surroundings. A closed system can exchange energy but not matter with its surroundings. An isolated system cannot exchange either matter or energy with its surroundings.
Q: What is the relationship between pressure, volume, and temperature in an ideal gas?
A:
For an ideal gas, the relationship between pressure (P), volume (V), and temperature (T) is described by the ideal gas law: PV = nRT, where n is the number of moles of gas and R is the gas constant. This equation shows that these variables are interconnected and changing one affects the others.
Q: What is the Carnot cycle and why is it important?
A:
The Carnot cycle is a theoretical thermodynamic cycle that represents the most efficient possible heat engine between two given temperatures. It's important because it sets the upper limit for the efficiency of any real heat engine and helps us understand the fundamental limitations of energy conversion.

Process of Thermodynamics

When there is an energetic shift within a system that is related with changes in pressure, volume, and internal energy, it is called a thermodynamic process.

There are four different types of thermodynamic processes, each with its own set of characteristics:

  1. Adiabatic process - A adiabatic process is one in which no heat is transferred into or out of the system.
  2. Isochoric Process - A process in which there is no change in volume and no work is done by the system.
  3. Isobaric Process - When there is no change in pressure, the process is called isobaric.
  4. Isothermal Process - A process in which the temperature does not change.

Properties: extensive and intensive

  1. The value of an intensive property is independent of the amount or size of matter present in the system. Temperature, density, and pressure are only a few examples.
  2. Extensive property: This is a property whose value is proportional to the amount or size of matter in the system. Consider the following examples: mass and total volume.

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NCERT Physics Notes:

Commonly Asked Questions

Q: What is thermal equilibrium?
A:
Thermal equilibrium is the state in which two or more objects in contact with each other have reached the same temperature. At this point, there is no net flow of thermal energy between the objects.
Q: What is entropy and how does it relate to the second law of thermodynamics?
A:
Entropy is a measure of the disorder or randomness in a system. The second law of thermodynamics states that the entropy of an isolated system always increases over time. This law explains why certain processes are irreversible and why heat always flows from hot to cold objects.
Q: What are the four laws of thermodynamics?
A:
The four laws of thermodynamics are:
Q: What is the difference between heat and temperature?
A:
Heat is the transfer of thermal energy between objects, while temperature is a measure of the average kinetic energy of particles in an object. Heat flows from objects with higher temperature to those with lower temperature.
Q: How does the first law of thermodynamics relate to energy conservation?
A:
The first law of thermodynamics is essentially the law of conservation of energy applied to thermodynamic systems. It states that energy cannot be created or destroyed, only converted from one form to another. This means that the total energy of an isolated system remains constant.

Frequently Asked Questions (FAQs)

Q: How does the concept of exergy destruction relate to the efficiency of real processes?
A:
Exergy destruction is the loss of useful work potential due to irreversibilities in a process. It's directly related to entropy generation. By quantifying exergy destruction, engineers can identify the most significant sources of inefficiency in a system and work to improve overall process efficiency. This concept is crucial in fields like
Q: What is the thermodynamic basis for the Leidenfrost effect?
A:
The Leidenfrost effect occurs when a liquid comes into contact with a surface significantly hotter than its boiling point. A vapor layer forms between the liquid and the surface, insulating the bulk of the liquid and causing it to hover. This effect is an example of film boiling and demonstrates the complex interplay between heat transfer, phase change, and fluid dynamics in extreme temperature gradients.
Q: What is the Le Chatelier principle and how does it relate to thermodynamic equilibrium?
A:
The Le Chatelier principle states that when a system at equilibrium is subjected to a change, the system will adjust to partially counteract that change. This principle is a consequence of the second law of thermodynamics and helps predict how chemical and physical equilibria respond to changes in conditions like temperature, pressure, or concentration.
Q: How does the concept of microstates relate to entropy?
A:
Microstates are the different possible arrangements of particles in a system. Entropy is related to the number of microstates: the more microstates available to a system, the higher its entropy. This connection provides a statistical interpretation of the second law of thermodynamics.
Q: What is the significance of the Boltzmann constant in thermodynamics?
A:
The Boltzmann constant (k) relates the average kinetic energy of particles in a gas with the temperature of the gas. It serves as a bridge between the microscopic and macroscopic descriptions of thermodynamic systems and plays a crucial role in statistical mechanics.
Q: How does the concept of fugacity extend the ideal gas law to real gases?
A:
Fugacity is a measure of the tendency of a substance to escape from a phase. It can be thought of as an "effective pressure" that accounts for the non-ideal behavior of real gases. The concept of fugacity allows thermodynamic equations developed for ideal gases to be applied to real gases with appropriate corrections.
Q: What is the thermodynamic basis for the Mpemba effect, where hot water can freeze faster than cold water under certain conditions?
A:
The Mpemba effect is a counterintuitive phenomenon that lacks a single, universally accepted explanation. Thermodynamic factors that may contribute include evaporation, convection currents, dissolved gases, and supercooling. The effect highlights the complexity of real-world thermodynamic systems and the limitations of simplified models.
Q: How does the concept of enthalpy help in understanding heat transfer in constant pressure processes?
A:
Enthalpy is a measure of the total heat content of a system. At constant pressure, the change in enthalpy of a system is equal to the heat transferred to or from the system. This makes enthalpy particularly useful for analyzing processes like chemical reactions or phase changes that occur at constant pressure.
Q: What is the relationship between the Helmholtz free energy and the work done by a system?
A:
The Helmholtz free energy (A) is defined as A = U - TS, where U is internal energy, T is temperature, and S is entropy. The change in Helmholtz free energy represents the maximum work that can be extracted from a closed system at constant temperature. This concept is particularly useful in analyzing processes where volume and temperature are held constant.
Q: How does the concept of partial molar quantities help in understanding the thermodynamics of mixtures?
A:
Partial molar quantities describe how an extensive property of a mixture changes when the amount of one component is varied while keeping the amounts of all other components constant. This concept is crucial for understanding the behavior of solutions and for calculating thermodynamic properties of mixtures from those of pure components.
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