Which of the following examples of a spontaneous reaction does not involve a chemical energy difference?
In order to produce a chemical energy difference, chemical bonds must be broken and reformed. As chemicals seek lower energy states, the spontaneous chemical reactions that occur release energy. The first two options are combustion reactions that definitely involve a chemical energy difference since heat is being produced. The same is true with the fourth choice. If you’re not careful, mixing a strong acid like HCl and water can bubble and splash. This is due to the dissolution of HCl in water. Again, the chemical energy difference can be observed by noting that the aqueous solution formed is warmer than what the water started out. So the answer is the glider landing. This is just a mechanical energy difference due to the loss of potential energy.
