Write true or false for the following statement:
During endothermic reactions,heat is transferred from the reacting substances to the surroundings.

What type of coating is formed on copper articles when they get corroded?

What happens when a piece of aluminium metal is added to dilute hydrochloric acid?

Write true or false for the following statement:
The thermal decomposition reaction of calcium sulphate (gypsum) is used in black and white photography.

Write the essential condition for the following reaction to take place: $2 AgCl \rightarrow 2 Ag + Cl_{2}$ and write one use of this reaction.

$A$ metal $X$ acquires a green colour coating on its surface on exposure to air.
$(i)$ Identify the metal $X$ and name the process responsible for this change.
$(ii)$ Name and write the chemical formula of the green coating formed on the metal.
$(iii)$ List two important methods to prevent this process.