Why is a drip irrigation system more sustainable than traditional spraying methods of irrigating crops? a. it leads to reduced river flow. b. it causes the water table to drop. c. it reduces pollution from runoff. d. it decreases water quality.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.