Are the following processes exothermic or endothermic?
a) When solid $KBr$ is dissolved in water, the solution gets colder.
b) Natural gas ($CH_4$) is burned in a surface.
c) When concentrated $H_2SO_4$ is added to water, the solution gets very hot.
d) Water is boiled in a teakettle.
Attempt at solution: For a), I would say that it is exothermic, since the solution gets colder, which means that it releases contained heat to the surroundings.
b) is exothermic evidently.
c) By the same reasoning, the solution is getting very hot, so it must be endothermic since it absorbs heat.
d) Not sure about this one. I would say endothermic, because the absorbed heat makes it boil.
This is what I answered, and apparently I made atleast two mistakes. So can someone explain to me the flaws in my reasoning?