Which of the following gases is of brown colour?

Malachite is an ore of which metal?

Of the three metals $X, Y$ and $Z$,$X$ reacts with cold water,$Y$ with hot water,and $Z$ with steam only. Identify $X, Y$ and $Z$ and also arrange them in the order of increasing reactivity.

Which of the following metals exist in their native state in nature?
$(i)$ $Au$
$(ii)$ $Cu$
$(iii)$ $Ag$
$(iv)$ $Fe$

Which furnace is used to extract iron metal from its ore?

Which of the following metals is soft enough to be cut easily with a knife?