The combustion of a compound refers to the reaction of that compound with oxygen to produce heat and light. In reactions (1) and (4) above, ethanol and methane reacted with oxygen to yield carbon dioxde and water. This is a combustion reaction.
Reaction(2) is a double replacement reaction because the both cations exchange their anion partners in the product.
Reaction (3) is a combination reaction. It involves the joining of two elements to form a new compound.
