The symptoms of hay fever include: 1  frequent sneezing. 2  runny or blocked nose. 3  itchy, red or watery eyes (allergic conjunctivitis)  an itchy throat, mouth, nose and 1  ears. cough, caused by postnasal drip (mucus dripping down the throat from the back of the nose)
Definition. noun, plural: chemical reactions. A process in which one or more substances (reactants) are chemically changed into one or more new substances (products).Chemical changes may involve motion of electrons in the forming and breaking of chemical bonds.Supplement. process in which one or more substances (reactants) are chemically changed into one or more new substances (products). Chemical changes may involve motion of electrons in the forming and breaking of chemical bonds. Supplement.
chemical decomposition reaction, decomposition reaction, decomposition - (chemistry) separation of a substance into two or more substances that may differ from each other and from the original substance.