Which one of the following metals does not react with cold as well as hot water?

Define alloys. List the properties of alloys that make them useful over pure metals. Explain this fact with suitable examples.

Zinc liberates hydrogen gas when reacted with dilute hydrochloric acid,whereas copper does not. Explain why?

$A$ solution of $CuSO_{4}$ was kept in an iron pot. After a few days,the iron pot was found to have a number of holes in it. Explain the reason in terms of reactivity. Write the equation of the reaction involved.

Differentiate between metal and non-metal on the basis of their chemical properties.

$A$ man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?