Chemical reaction , a process in which one or more substances , the reactant,are converted to one or more different substances ,the products. substances are either chemical elements or compounds .A chemical reaction rearranges the constituent atoms of the reactants to create different substances as products. The processes ,in which a substance or substances undergo a chemical change to produce new substance or substances, with entirely new properties.
Endothermic reactions are chemical reactions in which the reactants absorb heat energy from the surroundings to form products. These reactions lower the temperature of their surrounding area, thereby creating a cooling effect. Physical processes can be endothermic as well – Ice cubes absorb heat energy from their surroundings and melt to form liquid water (no chemical bonds are broken or formed).
Example of Endothermic reaction
In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change ΔH⚬ is negative."[1][2] Exothermic reactions usually release heat. The term is often confused with exergonic reaction, which IUPAC defines as "... a reaction for which the overall standard Gibbs energy change ΔG⚬ is negative."[2] A strongly exothermic reaction will usually also be exergonic because ΔH⚬ makes a major contribution to ΔG⚬. Most of the spectacular chemical reactions that are demonstrated in classrooms are exothermic and exergonic. The opposite is an endothermic reaction, which usually takes up heat and is driven by an entropy increase in the system.
Examples of Exothermic reactions