Energy, Open-Closed Systems, Endo-Exothermic, State Functions, & Work

Energy is the capacity to do work

• Radiant Energy comes from the sun and is the main source of energy on earth
• Thermal Energy is the energy associated with the random motions of atoms and molecules
• Chemical Energy is the energy that is stored in the chemical bonds of substances
• Nuclear Energy is the energy stored within the neutrons and protons in the nucleus of the atom
• Potential Energy is the energy available by virtue of an object's position 

Energy Changes in Chemical Reactions

• Heat is the transfer of thermal energy between  two bodies that are at different temperatures
• Temperature is a measure of the thermal energy
• Temperature DOES NOT equal thermal energy.

Open-Closed Systems 

• Thermochemistry is the study of heat change in chemical reactions
• The system is the specific part of the universe that is of interest in a particular study (the universe is "everything else".)
• Open system = allows the exchange of both energy and mass with surroundings
• Closed system = allows the exchange of but not mass
• Isolated system = allows neither energy nor mass to be exchanged (such as putting something in a vacuum jacket)

Endo-Exothermic Systems

• Exothermic process is any process that gives off heat (transfers thermal energy) from the system to the surroundings

2H2 (g) + O2 (g) => 2H2O (l) + ENERGY

H2O (s) => H2O (l) + ENERGY

• Endothermic process is any process in which heat has to be supplied to the system from the surroundings

ENERGY + 2HgO (s) => 2Hg (l) + O2 (g)

ENERGY + H2O (l) => H2O (g)

State Functions

• Thermodynamics is the scientific study of the interconversion of heat and other kinds of energy
• State functions are thermodynamic properties that are determined by the state of the system (at any time) regardless of how that condition was achieved 
• Energy, pressure, volume, temperature
• First law of thermodynamics - energy can be converted from one form to another, but cannot be created of destroyed

• ΔU = q + w
• ΔU is the change of the internal energy of the system
• q is the heat exchange between the system and the surroundings
• w is the work done on, or by, the system
• W = -PΔV is when a gas expands against a constant external pressure

Work

• Work done by the system on the surroundings
• w = F x d
• W = -PΔV
• PV = F/d*2 x d*3 = F x d = w
• Work is NOT a state function!!
• ΔV = V (final) - V (initial)