PHYISCS - LAW OF EQUIPARTITION OF ENERGY .pptx

THIS ppt will help you to understand some of the physics concepts very easily..!!!

1. PROJECT To study the concept of law of Equipartition of energy on basis of that explain degree of freedom of mono , di and polyatomic Gases.

2. INDEX DEGREE OF FREEDOM OF GAS MOLECULES TYPES OF MOTION DOF OF MONOATOMIC GAS DOF FOR DIATOMIC GAS DOF OF TRIATOMIC GAS TABLE LAW OF EQUIPARTITION OF ENERGY

3. Molecular degrees of freedom refer to the number of ways a molecule in the gas phase may move, rotate, or vibrate in space. It is defined as the number of coordinates required to specify the position of all the atoms in a molecule. Three coordinates x, y and z are required to specify the position of one atom in space. DEGREE OF FREEDOM OF GAS MOLECULES The molecule containing ‘n’ atoms will have 3n degrees of freedom which are distributed among the different kinds of motion. The translational motion The rotational motion The vibrational motion

4. • Mechanical phenomenon whereby oscillations occur about an equilibrium point. • The motion by which a molecule shifts from one point in space to another. • The movement of a molecule around an axis. A. The translational motion B. The rotational motion C. The vibrational motion Types of Motion

5. A monatomic molecule consists of only a single atom of point mass hence it has three degrees of freedom of translatory motion along the three coordinate axes x, y and z.  Degree of freedom of monoatomic gas Examples : Molecules of Inert gases like helium(He), Neon(Ne), Argon( Ar ), etc.

6. The diatomic molecule can rotate about any axis at right angles to its own axis. Hence it has  two  rotational degrees of freedom ,in addition it has  three  translational degrees of freedom along the three axes. A diatomic molecule shows  one  vibrational degree of freedom. So, a diatomic molecule has a total of  six  degrees of freedom at high temperature.  At room temperature the total degree of freedom of a diatomic molecule is  Five  because vibrational motion is not contributed. Degree of freedom of di atomic gas Examples: molecules of O 2 , N 2 , CO, Cl 2 , etc.

7. Degree of freedom of triatomic gas Examples : molecules of H 2 O, SO 2 , etc. In triatomic molecule the center of mass lies at the central atom.  It have   three  degrees of freedom of translation and  two  degrees of freedom of rotation and five  degrees of freedom at room temp. At high temperatures, It shows four vibrational degrees of freedom. Hence, it shows a total of  nine  degrees of freedom. At room temperature a triatomic  nonlinear molecule  possesses  three  degrees of freedom of rotation in addition to  three  degrees of freedom of translation. Hence it has  six  degrees of freedom.  At high temperatures, it shows a total of  nine  degrees of freedom.

8. Law of Equipartition of Energy For a system in equilibrium, there is an average energy of ½ kT or ½ RT per molecule associated with each degree of freedom. (where k = Boltzmann constant and T is the temperature of the system). This energy associated with each degree of freedom is in the form of kinetic energy and potential energy.  One translational degree of freedom = ½ kT or ½ RT One rotational degree of freedom= ½ kT or ½ RT One vibrational degree of freedom=  kT or RT Note:  As regard the vibrational motion the two atoms oscillate against each other therefore both potential and kinetic energy the energy of vibration involve two degree of freedom, so that vibrational motion in a molecule is associated with energy= 2 x  ½ kT =  kT Total energy E= E tr  + E rot  + E vib  + E elc

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