Endothermic: A process in which the system gains/absorbs energy from the surroundings.
Exothermic: A process in which the system loses/releases energy to the surroundings.
Chemical Reactions
In chemical reactions, bonds are broken and reformed.
Breaking bonds is an endothermic process. The reactants absorb energy until bonds between atoms break.
Forming new bonds is an exothermic process. As the products form, atoms become more stable. If you recall, when atoms gain stability, they release energy. So as these atoms form new bonds, energy is released.
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