What is the shape of monoclinic sulphur?

What is the process of depositing a layer of gold on silver called?

Which alloy is used to prepare scientific balance?

What happens when:
$(i)$ $A$ piece of calcium is dropped in water.
$(ii)$ Sodium is kept exposed in air.
$(iii)$ Iron nail is dipped in copper sulphate solution.
$(iv)$ Potassium is dropped in cold water.
$(v)$ Carbon dioxide is compressed in water at high pressure.
Give chemical equations involved in all the above reactions and balance them.

Write chemical equations for the reactions taking place when:
$(i)$ Iron reacts with steam.
$(ii)$ Magnesium $(Mg)$ reacts with dilute $HCl$.
$(iii)$ Copper is heated in air.

Make correct pairs from the below-mentioned $X$ and $Y$:

$X$	$Y$
$1.$ Dehydrating agent	$p.$ Sulphur dioxide gas
$2.$ In preparation of firecrackers	$q.$ Concentrated sulphuric acid
$3.$ Weak bleaching agent	$r.$ Dihydrogen gas
$4.$ Lightest gas	$s.$ Sulphur