Explain why a mixture of copper oxide and magnesium reacts when heated while there is no reaction when a mixture of copper and magnesium oxide is heated.

Is this a single replacement reaction or there is no

May someone me with these science questions

Water is initially present in a state where its molecules are far apart. during a change of state, its molecules slow down. which change of state has most likely taken place? from a gas to a liquid from a liquid to a gas from a solid to a liquid from a gas to a plasma