Energy categorization, chemical

Hazards associated with chemical reactions depend on the energy that can evolve in the course of reaction. The chemical reaction energy is categorized in Table 5.4-32 (based on data of Hoffman, 1985, and Rogers, 1997). 

In thermodynamics the state of a system is specified in terms of macroscopic state variables such as volume, V, temperature, T, pressure,/ , and the number of moles of the chemical constituents i, tij. The laws of thermodynamics are founded on the concepts of internal energy (U), and entropy (S), which are functions of the state variables. Thermodynamic variables are categorized as intensive or extensive. Variables that are proportional to the size of the system (e.g. volume and internal energy) are called extensive variables, whereas variables that specify a property that is independent of the size of the system (e.g. temperature and pressure) are called intensive variables. 

Vitamins are exogenous chemical substance required by the body in very small amount for the various metabolic functions of the body and categorized as essential nutrients. They do not yield energy but enable the body to use other nutrients and are primarily used in the prevention and treatment of certain deficiency diseases. 

It must be emphasized diat angle strain, torsional strain, and transannular strain are simply terms invented by chemists to categorize structural features in rings which lead to increased energy (strain). The molecules diemselves adopt structures which are the most stable and have die greatest amount of bonding energy. Nevertheless, strain is an important feature in molecules to keep in mind since it is manifested by altered chemical reactivity. 

Luminescence processes may be categorized by the excitation method used with any particular luminescent molecule. Photoluminescence is the excitation process that involves the interaction of electromagnetic radiation with photons. The process is termed chemiluminescence when the exciting energy results from a chemical reaction. Any luminescence arising from an organism is referred to as bioluminescence. 

Metabolic reactions are categorized into two types, anabolic and catabolic. Anabolic reactions construct complex molecules from simple molecules, usually while using up energy that becomes stored in chemical bonds. Catabolic reactions break down complex molecules into multiple simple molecules, usually while releasing energy. 

The term explosion is best defined as a process that involves a sudden release of energy resulting in a rapid and significant buildup of overpressure. Explosions can be categorized into physical/mechanical and chemical explosions. For example, an explosion caused by a sudden release of compressed gas is a physical explosion. A chemical explosion is caused by a chemical reaction(s), which could be combustion, exothermic decomposition or exothermic reaction. Chemical explosions can occur in gas, liquid or solid phase. Chemical explosions that occur in liquid and solid phases are sometimes called condensed phase explosions. Explosive explosions fall in this category. 

---