Why is burning of coal considered a chemical change?

In the following situation, a reaction may or may not take place. If it does, write the balanced molecular, total ionic and net ionic equations illustrating the reaction. Assume the reaction takes place in aqueous solutions.

• Some iron nails are placed in ${\mathrm{CuCl}}_2$ solution.

In the following situation, a reaction may or may not take place. If it does, write the balanced molecular, total ionic and net ionic equations illustrating the reaction. Assume the reaction takes place in aqueous solutions.

• Some coins are dropped in hydrochloric acid solution.

In the following situation, a reaction may or may not take place. If it does, write the balanced molecular, total ionic and net ionic equations illustrating the reaction. Assume the reaction takes place in aqueous solutions.

• A copper wire is placed in $\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2$ solution.

Below are given two chemical reactions :

(i) $2{\mathrm{KBr}}_{\left(\mathrm{aq}\right)} + {\mathrm{Cl}}_{2\left(\mathrm{aq}\right)}\to 2{\mathrm{KCl}}_{\left(\mathrm{aq}\right)} + {\mathrm{Br}}_{2\left(\mathrm{aq}\right)}$

(ii) ${\mathrm{Fe}}_{\left(\mathrm{s}\right)} + {\mathrm{S}}_{\left(\mathrm{s}\right)}\to {\mathrm{FeS}}_{\left(\mathrm{s}\right)}$

Which is a combination reaction, and which is the displacement reaction? Give an explanation also.