### action | chemical action | chemical reaction:

Chain reaction
* Most chain reaction spreads to water sources.
* Some chain reaction causes explosions
  - extinction
  - nuclear explosions
  - destroys substances
  - leads to degradations
  - releases heat
* can rapidly grow.
* escalates To economists, excess inventories are a classic cause of recession.
* is chemical reaction
  - nuclear reaction
* provides power.
* spreads to sources

Endergonic reaction
* are energy-storing reactions
  - important to many cell processes
* require an energy input
  - input of energy
* result in products with more energy than the reactants had.

### action | chemical action | chemical reaction:

Endothermic reaction
* All endothermic reactions decrease the entropy of the sorroundings
  - occur spontaneously
* Most endothermic reaction gives off energy.
* Some endothermic reactions proceed spontaneously.
* absorb energy
* can be cold enough to cause frost bite.
  - endergonic reaction
* needs energy.
* require heat.
* take in heat.
+ Thermochemistry: Physical chemistry
  * Endothermic reactions take in heat. Exothermic reactions give out heat. Thermochemistry combines the concepts of thermodynamics with the idea of energy in the form of chemical bonds. It includes calculations of such quantities as heat capacity, heat of combustion, heat of formation, enthalpy, entropy, free energy, and calories.

Exergonic reaction
* are biochemical reactions that liberate only heat
  - energy-releasing reactions
* have a negative G and energy is released.
* produce an energy output.
* release energy.
* result in products with less energy than the reactants had.

### action | chemical action | chemical reaction:

Exothermic reaction
* All exothermic reactions are spontaneous
* Some exothermic reaction produces gaseous products
  - gases
  - hot gases
* are more likely to occur spontaneously
  - often spontaneous
* can be violent.
* involving hydrogen occur when heated or in contact with moisture or acids.
  - exergonic reaction
* liberate energy.
* produce heat, whereas endothermic reactions take heat in.
* release energy as the reaction proceeds
  - into the environment - feel hot
  * Endothermic reactions take in heat. Exothermic reactions give out heat. Thermochemistry combines the concepts of thermodynamics with the idea of energy in the form of chemical bonds. It includes calculations of such quantities as heat capacity, heat of combustion, heat of formation, enthalpy, entropy, free energy, and calories.

Oxidation reaction
* Many oxidation reactions occur everyday without releasing fire, however.
* are exergonic and reduction reactions are endergonic.
* involve electron loss and are exergonic
  - reduction reactions involve electron gain
  - the transfer of electrons
* occur when a chemical substance loses electrons to another substance.

Photochemical reaction
* Some Photochemical reactions leads to the generation of highly reactive species.
* are classified as being either direct or indirect
  - common in nature
  - limited to the soil surface

Reduction reaction
* Most reduction reaction occurs in reductions.
* Some reduction reaction produces gases
  - hydrogen gases
* involve electron gain and are endergonic.
* is chemical reaction
  - issuing
* means addition of hydrogen to a reaction.
  - on the cathode