[kenny1999]

can "melting", "boiling" considered as endothermic REACTION?
Since they are physical changes. Strictly speaking I am not sure if they can be considered as a REACTION

another thing
why the mix of conc acid with water is exothermic? should it be considered in terms of intermolecular force? What is the dominant attraction between acids in its pure state?

Thanks!

[bakerbg]

boiling and melting are not chemical reactions - simply physical changes that require energy.
conc acid actually reacts with water. the products of this reaction releases more energy that that which is required to break up the reactants, thus the reaction is exothermic.

acids contain charged particles, what kind of intermolecular forces do you think exists between them?

[kenny1999]

boiling and melting are not chemical reactions - simply physical changes that require energy.
conc acid actually reacts with water. the products of this reaction releases more energy that that which is required to break up the reactants, thus the reaction is exothermic.

acids contain charged particles, what kind of intermolecular forces do you think exists between them?

how does the acid react with water? do you mean ionization of the acid molecule into hydrogen ion and its ion salt?

in my opinion, between water molecules in pure water there is hydrogen bond. When it mixes with sulphuric acid or say HCl, especially HCl it can't form hydrogen bond with itself or water. I think water molecules should prefer H-bond... how come HCl or other acid will dissolve?

Please answer with simpler English , please,  I am not native Eng