From Wikipedia, the free encyclopedia. The environmental impacts of irrigation relate to the changes in quantity and quality of soil and water as a result of irrigation and the effects on natural and social conditions in river basins and downstream of an irrigation scheme.
Combustion reactions can only be exothermic. In chemical reactions, old bonds are broken to form new ones. Depending on the energy difference between broken and formed bonds, the total reaction energy is either positive or negative.
For example; iron + sulphur = iron sulphide (Black fillings) (Yellow powder) = (Black solid) Energy is taken in or given out, during the reaction. A reaction, which gives out heat energy, is known as exothermic (link). A reaction, which takes in heat energy, is endothermic (link). For example: Fireworks are exothermic, as is the reaction above. Frying eggs is an endothermic reaction. Reactions not only produce heat but light and sound. The change is usually difficult to reverse. Several reactions would have to be carried out to get iron and sulphur from iron sulphide. Source(s): http://www.lcc.ukf.net/KS3Chem/chemphych...