I wanted to ask for examples of spontaneous chemical reactions meaning that their enthalpy would be negative (exothermic) and their variation of entropy would increase, therefore the Gibbs energy would be also negative and the reactions would be spontaneous at all temperatures (?).
I was thinking about the boiling of water as the reaction feels hot and the entropy change is positive as it goes from liquid to gas (entropy increases) but then I thought that to do that, we need an external energy and so the reaction would be non-spontaneous?
Another one could be dropping mentos into a carbonated drink. I can be sure that the reaction doesn't requiere an external force to happen BUT the reaction itself doesn't feel hot (I think I saw it once when they did it in primary school but I'm assuming it isn't releasing any heat?)
I know that when enthalpy is negative and entropy is negative, it would only be spontaneous if the temperature was low enough.
For the non spontaneous reactions, I can't really think about one that has positive enthalpy and negative entropy. I CAN think of a reaction that needs a push to "occur" like taking off a stain of a shirt or even a reaction of decomposition of water into h2 and o2.
I think I'm getting something wrong.