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.
Decomposition Reaction Defined. A chemical reaction is a process by which the atoms of one or more substances are rearranged to form different substances. There are many types of chemical reactions. These reactions are often classified by what they form or what happens during the course of the reaction.A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more elements or new compounds.hese reactions are often classified by what they form or what happens during the course of the reaction. A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more elements or new compounds.