Write a short note on exothermic, endothermic, photochemical and electrochemical reactions with examples.
Answers
1.Exothermic reactions are reactions that release energy into the environment in the form of heat. Exothermic reactions feel warm or hot or may even be explosive.
More energy is released making chemical bonds than is used breaking them. In an exothermic reaction, the enthalpy change has a negative value: ΔH < 0
2.Endothermic Reaction – An endothermic reaction is the opposite of an exothermic reaction. Heat is absorbed in an endothermic reaction. In an exothermic reaction, the enthalpy change has a positive value: ΔH > 0
3.Photochemical reaction, is a chemical reaction initiated by the absorption of energy in the form of light. The consequence of molecules' absorbing light is the creation of transient excited states whose chemical and physical properties differ greatly from the original molecules.
4.An electrochemical reaction is a process in which electrons flow between a solid electrode and substance, such as an electrolyte. This flow triggers an electric current through the electrodes, causing the reaction to liberate or absorb heat.
An exothermic reaction is a chemical reaction that releases energy through light or heat. It is the opposite of an endothermic reaction.
An example would be a bonfire on the beach.
Endothermic reaction: Any chemical reaction or change in which energy in the form of heat is absorbed
An example would be melting ice on a hot summer day.