When a drop of water is added to a mixture of chemicals a blue flame and smoke are produced Oxidation of Zinc

Purpose n To observe an oxidation reaction of a metal n To observe an exothermic reaction

Demonstration n The reaction was Zn(s) + NH 4 NO 3 (s) n The zinc was oxidized by the ammonium nitrate n The smoke in the reaction was fine zinc oxide n When iodine was added to the reaction it underwent sublimation I 2 (g) N 2 (g) + ZnO(s) + 2H 2 O(g) I 2 (s) purple

Concepts 1.Oxidation of a Metal 2.Oxidizing Agents 3.Sublimation

1.Oxidation of a Metal n Metallic elements hold their electrons more loosely (not as tightly) as non-metallic elements n Metals tend to lose electrons to other substances n Zinc loses its two outermost electrons to form Zn 2+ n Zinc combines with oxygen in this demonstration

2.Oxidizing Agents n Oxidizing agents are substances that cause other substances to be oxidized n Oxidizing agents frequently contain oxygen which is transferred to the substance which is oxidized n Ammonium nitrate is the oxidizing agent in this demonstration

3.Sublimation Solid Liquid Gas melting freezing boiling condensation s u b l i m a t i o n Liquid Solid

Conclusions n Zinc metal was oxidized to zinc oxide in an exothermic reaction n The heat liberated in the reaction caused the iodine to undergo sublimation to purple iodine vapor

Comments n The reaction is a fast reaction because of zinc powder is used which has a high surface area n Water is a catalyst which serves to initiate the reaction n Sublimation is the reason that clothes can dry outside in the wind on in sub- zero temperatures: ice converts to water vapor