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

What is the colour of $FeSO_{4} \cdot 7H_{2}O$ crystals? How does this colour change upon heating? Give the balanced chemical equation for the change.

Which among the following is(are) double displacement reaction$(s)$?
$(i)$ $Pb + CuCl_2 \longrightarrow PbCl_2 + Cu$
$(ii)$ $Na_2SO_4 + BaCl_2 \longrightarrow BaSO_4 + 2NaCl$
$(iii)$ $C + O_2 \longrightarrow CO_2$
$(iv)$ $CH_4 + 2O_2 \longrightarrow CO_2 + 2H_2O$

Name the oxidising and reducing agent in the following reaction:
$CuO + H_{2} \longrightarrow Cu + H_{2}O$

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.

$(a)$ Balance the chemical equation:
$Fe(s) + H_2O(g) \rightarrow Fe_3O_4(s) + H_2(g)$
$(b)$ Identify the type of reaction in the equation given below:
$Na_2SO_4(aq) + BaCl_2(aq) \rightarrow BaSO_4(s) + NaCl(aq)$