Write true or false for the following statement: On heating the crystals of ferrous sulphate,the colour changes from green to grey.

What can be seen when a strip of copper metal is placed in a solution of silver nitrate?

Translate the following reactions into balanced chemical equations:
$(i)$ Manganese dioxide is heated with aluminium powder.
$(ii)$ Iron is treated with steam.

The following reaction is used for the preparation of oxygen gas in the laboratory:
$2KClO_{3(s)} \xrightarrow[Catalyst]{Heat} 2KCl_{(s)} + 3O_{2(g)}$
Which of the following statement$(s)$ is(are) correct about the reaction?

Give reasons for the following:
$(i)$ Keeping food in airtight containers helps in preventing rancidity.

$A$ reddish-brown coloured metal, used in electrical wires, when powdered and heated strongly in an open china dish, its colour turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on the above information, answer the following questions:
$(i)$ Name the metal and the black coloured substance formed.
$(ii)$ Write balanced chemical equations for both the reactions.