What is an endothermic and exothermic reaction?

Endothermic and exothermic reactions are two fundamental types of chemical reactions that are categorized based on the heat exchange with the surroundings:

Endothermic Reaction:

In an endothermic reaction, energy is absorbed from the surroundings in the form of heat. This results in a decrease in the temperature of the surroundings.
Examples of endothermic reactions include the dissolution of ammonium nitrate in water, the reaction between citric acid and baking soda in a cold pack, and the decomposition of calcium carbonate in a blast furnace.
Exothermic Reaction:

In an exothermic reaction, energy is released to the surroundings in the form of heat. This results in an increase in the temperature of the surroundings.
Examples of exothermic reactions include combustion reactions like the burning of wood or gasoline, the reaction between vinegar and baking soda in a homemade volcano, and the reaction between sodium hydroxide and hydrochloric acid.
Understanding whether a reaction is endothermic or exothermic is crucial for various applications, from designing chemical processes to understanding the energy changes in biological systems.