exothermic solution

An exothermic solution is formed when two substances mix, and heat is released during the process. This is the opposite of an endothermic process, where heat is absorbed. Many common chemical reactions are exothermic, including the formation of compounds from their elements, such as water from hydrogen and oxygen, and the combustion of fuels.12

When substances combine to form a solution, heat is either released (exothermic) or absorbed (endothermic). An ideal solution is one where no heat effect occurs during mixing. Exothermic heats of solution are observed when the components interact strongly, like the reaction between sodium hydroxide and hydrogen chloride, which releases significant heat. Conversely, endothermic reactions require energy input, such as heating limestone to produce lime.12