Why iron rims are heated red hot before being put on the cart wheels?

When an iron nail is hammered, it becomes hot. Why?

Assertion: Current is passed through a metallic wire, heating it red. When cold water is poured on half of its portion, then rest of the half portion becomes more hot Reason: Resistance decreased due to decrease in temperature and so current through wire increases

Numbers from 1 to 50 are written on slips of paper and put in a box A slip is to be drawn from it, but before doing so, one must make a guess about the number: either prime number or a multiple of five Which is the better guess? Why?

Orthoboric acid on strong heating to red hot gives. metaboric acid borax boron tri oxide tetraboric acid

A heptahydrate of formula [M(H_(2)O)_(6)]SO_(4).H_(2)O is Isomorphous with white vitriol. The hydrated salt heated to 200^(@)C becomes anhydrous and when becomes red hot decomposed to its oxide SO_(2) and O_(2) . The compound is needle shaped solid used as purgative. It can be Identified with Na_(2)HPO_(4) . Identify the salt?