Deplacement reaction
A chemical reaction is a process in which one or more substances, called reactants, change into one or more completely new substances, called products. This happens because the atoms in the reactants rearrange themselves. During the reaction, old chemical bonds break and new chemical bonds form, creating substances with different properties, appearances, and uses. The atoms themselves are not created or destroyed—they are simply rearranged in a new way, so the total amount of matter remains the same. Many chemical reactions also involve energy. Some release energy as heat or light, while others absorb energy from their surroundings. Chemical reactions occur everywhere, from cooking food, burning fuel, and rusting iron to digestion, breathing, photosynthesis, and the production of medicines, making them essential for life and modern technology.