What does one mean by exothermic and endothermic reactions? Give examples.
A chemical reaction in which a large amount of heat / energy is produced along with the products is called exothermic reaction.
Calcium Oxide (Quick Lime) reacts with Water to produce Calcium Hydroxide (Slaked Lime) and Heat
CaO(s) + H 2 O(l) → Ca(OH) 2 (aq) + Heat
Since heat is produced / released in this reaction, this reaction is called an exothermic reaction
A chemical reaction in which a large amount of heat / energy is absorbed is called endothermic reaction.
On heating of Calcium Carbonate (limestone)
It decomposes into Calcium Oxide (Quick Lime) + Carbon Dioxide
CaCO 3 (s) → CaO(s) + CO 2 (g)
Since heat is absorbed in this reaction, this reaction is called an endothermic reaction.