Amount of substance in use in chemical engineering in the United States is the pound-mole, having the symbol lb-mol. One pound-mole is . When quoting an amount of substance, it is necessary to specify the entity involved, unless there is no risk of ambiguity. One mole of chlorine could refer either to chlorine atoms, as in 58.44 g of sodium chloride, or to chlorine molecules, as in 22.711 liters of chlorine gas at STP. The simplest way to avoid ambiguity is to replace the term "substance" by the name of the entity or to quote the empirical formula. For example: Amount of substance
Chemical change all the process involved in photosynthesis, a process in which carbon dioxide and water are changed into sugars and oxygen by plants, digestion in which energy rich materials are used by organisms to grow and move, Krebs cycle which liberates energy from stored reserves, protein synthesis which enable organisms to grow using processes controlled by RNA etc. The following can indicate that a chemical change has taken place, although this evidence is not conclusive: Chemical change Chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or