Energy Vocabulary

Chapter 8

  1. Energy: measure of a systems capacity to do work or supply heat
  2. System:  Region of primary concern from which energy flows out of or into.  The system might be nanoparticles in a container, or consists of the nanoparticles and the container.
  3. Surroundings: Everything that can change energy with the system,  If the system consists of nanoparticles in a container, the container could be considered the surroundings, if the container was perfectly insulated. If the system is the nanoparticles and container, the surroundings consist of things in contact with the outside of the container.   
  4. Universe:  The system plus the surroundings
  5. Work (W): energy expended during an act of moving an object a distance against an opposing force. W = -Fx
  6. Heat (q): energy (thermal) transferred as a result of a temperature difference between a system and the surroundings.
  7. Working and Heating: processes by which energy is transferred
  8. Law of Conservation of Energy: energy in not created or destroyed in a process, but can be changed in form. Total energy of the world is constant
  9. Thermodynamics: study of energy and its interconversion
  10. First Law of Thermodynamics: the energy of the Universe is constant.
  11. Potential energy: energy due to position or composition
    • gravitational: energy due to relative position of two objects with mass
    • electrostatic: energy due to position of charged particles
    • chemical potential: energy resulting from attractions among electrons and nuclei
  12. Kinetic energy: energy due to motion. KE = (1/2)mv2.
    • mechanical: energy of motion of macroscopic objects
    • thermal: energy of motion of nanoscopic objects
    • electrical: energy of motion of electron moving in a conductor
  13. Difference between heat and temperature:
    • Temperature measure of the average kinetic energy of the particles
    • Heat is energy (thermal) transferred due to temperature difference
  14. calorie (cal):  the energy required to raise the temperature of 1.00 g of pure water by 1.00 degree Celsius.   (the dietary cal is actual a Kcal)
  15. Joule (J):  A unit of energy, which is derived from other units.  1 J = 1.0 kg.m2/s2.   1 cal = 4.184 J.
  16. heat capacity:  quantity of energy required to increase the temperature of a sample by 1 degree C (unit = cal/oC).
  17. specific heat capacity:  quantity of energy required to increase the temperature of a 1 gram of sample by 1 degree C (unit = J/g.oC).
  18. molar  heat capacity:   quantity of energy required to increase the temperature of a 1 mol of sample by 1 degree C (unit = J/mol.oC).
  19. heat of fusion:  quantity of heat (thermal energy) required to melt 1 g of a solid at its melting point.
  20. heat of vaporization:  quantity of heat (thermal energy) required to evaporate 1 g of a liquid at its boiling point.
  21. Endothermic: a process in which thermal energy must be transferred into a thermodynamic system in order to maintain constant temperature
  22. Exothermic: a process in which thermal energy must be transferred out of  a thermodynamic system in order to maintain constant temperature
  23. Internal Energy (E): the total energy of a system; the sum of the individual energies of all substances in the system; the sum of the kinetic and potential energies of all substances in a system.
  24. First Law of Thermodynamics: Δ E = E2 - E1 = q + W = q - PΔV for PV work of gases. OR  Δ Euniv = Δ Esys + Δ Esurr = 0
  25. Enthalpy (H): H = E + PV
  26. Change in Enthalpy: Δ H = H2 - H1 = qp, where qp is the heat change at constant pressure. The quantity of thermal energy into a system at constant pressure.
  27. Bond Dissociation Energy (Bond Enthalpy):  The energy required to break a bond between two atoms in a molecule in the gaseous state to produce atoms in the gaseous state
  28. Hess's Law
  29. Standard State:  the pure form of a substance at standard pressure (1 bar), or for a solute at a concentration of 1 M.  (Note:  The standard state of H2O can be pure water at solid, liquid, or gaseous water - all pure water - at 1 bar).
  30. Standard reaction enthapy (Δ H0):  The reaction enthalpy when reactants in their standard state change into products in their standard state (many tables have data fro 250C for convenience only since the temperature is not defined for the standard state..   Note following:
    • Δ H0 will differ in combustion reactions, for example, depending on if pure water in the liquid or gaseous state at 1 bar is produced.
    • Δ H0'  is used for biological reactions in aqueous solutions (at 1 bar), when all reactants and products are at 1 M concentration except
      H+ = 1 x 10-7M,  since most biological reactions occur around pH 7 when H+   = H3O+ = 10-7 M (pH 7.0).
  31. Standard enthalpy of formation (Δ Hf0):  The standard reaction enthalpy per mole of substance for the synthesis of a compound from pure elements in their most stable state at 1 bar and at a specified temperature.
  32. Standard enthalpy of combustion (Δ Hc0):  The standard reaction enthalpy per mole of substance for the complete combustion of a compound under standard condition (standard state and 1 bar).