Final answer:
The reaction between aluminum and oxygen is exothermic, as it releases heat and is associated with a decrease in enthalpy. Similar exothermic reactions include the formation of water from hydrogen and oxygen, and the combustion of methane to produce carbon dioxide and water.
Step-by-step explanation:
The reaction between aluminum and oxygen, represented as 2Al(s) + 3/2 O₂(g), refers to the formation of aluminum oxide and is known to be an exothermic reaction. This means that the reaction releases heat into the surrounding environment, as energy is given off when the bonds in the products are formed. This process is associated with a decrease in the system's enthalpy (ΔH), and thus, ΔH is negative. According to the enthalpy of reaction, if heat flows from the system to its surroundings, and the enthalpy of the system decreases, the reaction is exothermic. Moreover, the reaction of hydrogen gas (H₂) with oxygen (O₂) to form water (H₂O) and the reaction between natural gas (methane, CH4) and oxygen to form carbon dioxide (CO₂) and water are also exothermic reactions because the chemical equations show heat being released in the process.