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Back Chemical Chemical Engineering Dictionary Thermodynamics Internal Energy Definition, Concept and Types of Energy

Internal Energy Definition, Concept and Types of Energy

Definition:

This form of energy is stated as the summation of all microscopic forms of energy. It is defined as the sum of kinetic and potential energy of the molecule since it is related to the molecular structure and molecular activity.

Concept of Internal Energy in a system

Let us consider an example of internal energy. Imagine a system (gas in the container) at its molecular level. The molecules of gas move within the space of the container with some velocity.

Since, they move with some velocity they possess kinetic energy. This energy is known as translational energy. The atoms of the poly atomic molecule rotate about there axis. this energy is known as rotational kinetic energy. The atoms of the poly atomic molecule also vibrates. i. e move back and forth about their common center of mass. This energy is known as vibrational kinetic energy. The electron within nucleus rotate about their nucleus this energy is known as rotational kinetic energy. Electron in the outer orbit of an atom possesses greater kinetic energy.

Electron in the orbits also spins around their axes this energy is known as spin energy. Proton and neutron in the nucleus of an atom also possess spin energy. The kinetic energy of molecules in the system is called sensible energy. The average velocity and movement of molecule is dependent upon the temperature of the gas. As the temperature increases velocity and movement increases thereby increasing kinetic energy of the system and ultimately internal energy of the system also gets increased.

The internal energy of a substance is also concerned with the binding forces between the molecules the system, between the atom inside a molecule, and between the particles within an atom and its nucleus. The molecular binding force is greater in solid than in gases. When sufficient energy is provided to the solid or liquid then binding force is over come by this force and substance turns into gas. This process is known as phase change process. During a phase change process there is no composition change throughout the system. i. e composition remain constant

In the nucleus of an atom proton ad neutron are bound together by a strong nuclear force. Electron outside the nucleus in their orbit revolves around it with the help of nuclear force. The internal energy related to the atomic bonds in the molecule is referred as chemical energy.

When a chemical reaction such as combustion reaction takes place some chemical bonds are destroyed while new bonds are formed. The nucleus forces are much greater than the chemical energy within atom. This greater amount of energy associated with the strong bond in the nucleus is referred to as Nuclear energy. During a chemical reaction structure of electron within an atom is changed while in nuclear reaction nucleus gets changed. Atoms also contain some electric and magnetic dipoles energy.

Types of Energy

The various forms of energy discussed above can be categorized in two forms.

  1. Static Energy
  2. Dynamic Energy

STATIC ENERGY

If total energy of the system can keep or store in a system then it is called static energy

DYNAMIC ENERGY

If total energy of the system cannot keep or store in a system is called dynamic energy or the energy in transition.

RECOGNITION OF DYNAMIC ENERGY

This form of energy is recognized when it crosses the boundary of a close system in the form of Heat and Work. These two forms represent the energy gained or lost by the system during a process .

In control volume system dynamic energy is recognized when it crosses the boundary in the form of mass transfer.

MACROSCOPIC KINETIC ENERGY

The kinetic energy of an object is defined as macroscopic kinetic energy. This form of energy describes the orderly motion of all molecules in on e direction along a straight path or around an axis. This form of energy is much more useful than the microscopic kinetic energy since it is very much organized.

MICROSCOPIC KINETIC ENERGY

The kinetic energy of molecule is defined as microscopic kinetic energy. This energy is highly random, undefined and disorganized. The main concern of thermodynamic is do convert the disorganized form of energy i.e. heat in to organized form of energy i. e. work

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