(a) With the help of an activity, explain the conditions under which iron articles get rusted. OR (b) (i) Name two metals which react violently with cold water. List any three observations which a student notes when these metal are dropped in a beaker containing water. (ii) Write a test to identify the gas evolved (if any) during the reaction of these metals with water.

(a) Iron articles get rusted when they come in contact with air and moisture. This is because iron reacts with oxygen and moisture to form iron oxide, also known as rust. (b) (i) Two metals that react violently with cold water are sodium and potassium. When these metals are dropped in a beaker containing water, the following observations are noted: The metal starts melting and moving rapidly on the surface of the water. The metal catches fire and burns with a yellow flame. The reaction produces a hissing sound. (ii) To identify the gas evolved during the reaction of these metals with water, a burning splint can be used. If the gas is hydrogen, it will burn with a pop sound when the burning splint is brought near it.