Chapter 2 thermodynamic

Alright guys time for next lesson. In the previous chapter we already know about the law of thermodynamic and also most of the introduction of what is about thermodynamic. Now we move to chapter 2 which is Energy, Energy Transfer, and General Energy Analysis

CHAPTER 2

Introduction

       In this chapter we will learn about the energy. All type of energy that are involve in general energy system analysis. Plus we will study about heat and work which also involved in the energy analysis. The first law of thermodynamics: energy can be neither created nor destroyed during a process; it can only change forms. Energy can transfer between a system and surroundings

                                                              Form of energy around us
                                                             Source: www.phibetaiota.net

Forms of Energy

Total E = sum of all energies
Macroscopic
-energy possesses as a whole with respect to an outside reference frame
- gravity, magnetism, electricity, and surface tension
- organized as a result of motion of all in one direction
Microscopic
- related to structure of a system
- degree of activity
- Independent of outside reference frame
- Internal Energy = sum of microscopic energies

Energy can exist in numerous forms:

•Internal energy: May be viewed as the sum of the kinetic and potential energies of the molecules.

•Sensible heat: The kinetic energy of the molecules.

•Latent heat: The internal energy associated with the phase of a system.

•Chemical (bond) energy: The internal energy associated with the atomic bonds in a molecule.

•Nuclear energy:  The internal energy associated with the bonds within the nucleus of the atom itself.

But in this chapter we will focus on internal energy

Kinetic and potential energies: two forms of mechanical energy. these two energy are existed in the total energy system(sometimes it doesn't).

                                                             kinetic and potential energy
                                                        source: bvg8science.wikispaces.com

Kinetic Energy

- Possessed by a system as a result of its motion relative to some reference frame

Potential Energy

      Since heat and work are path dependent functions, they have inexact differentials designated by the symbol d.  The differentials of heat and work are expressed as dQ and dW.  The integral of the differentials of heat and work over the process path gives the amount of heat or work transfer that occurred at the system boundary during a process.

how to write Q and W in test or exam or quiz

                                                  The correct way of
                                                 expressing Q and W

Heat and Work

-a quantity that is transferred to or from a system during an interaction is not a property

- the amount of such a quantity cannot be determined only by the state of a system


- thus, heat (Q) and work (W) are energy transfer mechanisms 



Similarities
1. recognized at the boundaries of a system as they cross the boundaries, they are boundary phenomena
2. Systems possess energy, but not heat or work
3. Both are associated with a process, i.e. there is no 'state heat or work' as their meaning does not change - unlike 'properties' which change with state
4. They are path functions (i.e., mag depends on the path of the process and the end states)

*Adiabatic process

-no heat transferred, Q = 0
- well insulated system = assume negligible heat transfer
- system/surrounding are same temp.

Summary

  

  The sum of all forms of energy of a system is called total energy, which is considered to consist of internal, kinetic, and potential energies. Internal energy represents the molecular energy of a system and may exist in sensible, latent, chemical, and nuclear forms.