1st law of thermodynamics

• Thermodynamic system


  A collection of objects that is convenient to regard as a unit
• Thermodynamic process


  A process in which there are changes in the state of a thermodynamic system
• Heat enters the system

  It is positive
• Heat leaves the system

  It is negative
• Work is done by the system

  It is positive
• Work is done on the system

  It is negative
• Thermodynamic quantities


  • Can be analyzed completely microscopically or macroscopically
• Microscopic analysis


  1. A wall strike would do no work if the wall is not movable

  2. It does positive work if the volume increases

  3. It does negative work if the volume decreases
• Infinitesimal


  Work done by the system doing a small expansion
• Path


  The intermediate state from initial to final, there are infinite paths possible
• Heat depends also on the path chosen
• Internal energy (U)


  Some of kinetic energies of all of its constituent particles plus the sum of the potential energies
• First law of thermodynamics

  Energy cannot be created nor be distort, it can only be transformed from one form to another
• Types of thermodynamic systems

  • Open system or study flow system
  • Closed system or non-flow system
  • Isolated system
• Types of thermodynamic processes

  • Reversible process (aka "quasi static process")
  • Irreversible process
  • Cyclic process
• Reversible process


  A process that can be reversed or can go back to its original state without a loss or dissipation of energy
• Irreversible process


  A process that proceeds spontaneously in one direction
• Cyclic process


  A process which gives the same state or conditions as the system undergoes a series of processes