Middle School Physical Science: Chemical Reactions - Chemical Reactions and Energy — Flashcards

In a chemical reaction, energy is used for either breaking the bonds of the reactants or in the formation of new bonds. So, there are two ways to produce the energy in a reaction i.e, in exothermic reaction or endothermic reaction.
 

Conservation of Energy: Whether a reaction absorbs energy or releases energy, there is no overall change in the amount of energy in a chemical reaction. That's because energy cannot be created or destroyed. This is the law of conservation of energy.    
Energy can change form—for example, from electricity to light—but the same amount of energy always remains.    
 

If energy cannot be destroyed, what happens to the energy that is absorbed in an endothermic reaction? The energy is stored in the chemical bonds of the products. This form of energy is called chemical energy.

In an endothermic reaction, the products have more stored chemical energy than the reactants.

In an exothermic reaction, the opposite is true. The products have less stored chemical energy than the reactants. The excess energy in the reactants is released to the surroundings when the reaction occurs.