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

Complete the missing components/variables given as $x$ and $y$ in the following reactions:
$(a)$ $Pb(NO_3)_2(aq) + 2KI(aq) \longrightarrow PbI_2(x) + 2KNO_3(y)$
$(b)$ $Cu(s) + 2AgNO_3(aq) \longrightarrow Cu(NO_3)_2(aq) + x(s)$

Give reasons for the following:
$(i)$ All decomposition reactions are endothermic reactions.
$(ii)$ Colour of copper sulphate solution changes when an iron nail is dipped in it.
$(iii)$ Respiration is an exothermic reaction.

Write one example for each of the decomposition reactions carried out with the help of:
$(i)$ electricity
$(ii)$ heat
$(iii)$ sunlight
Give balanced chemical equations in each case.

$A$ student has been collecting silver coins and copper coins. One day she observed a black coating on silver coins and a green coating on copper coins. Which chemical phenomenon is responsible for these coatings? Write the chemical name of black and green coatings.

$(a)$ Define corrosion.
$(b)$ What is corrosion of iron called?
$(c)$ How will you recognise the corrosion of silver?