Types of Chemical Reactions Chemical reactions involve the rearrangement of atoms to form new substances with different properties. There are two main types of...
Chemical reactions involve the rearrangement of atoms to form new substances with different properties. There are two main types of reactions based on energy changes:
Exothermic reactions release energy, usually in the form of heat, to the surroundings. During these reactions, the products have lower overall energy than the reactants, and the temperature of the surroundings increases.
Endothermic reactions absorb energy from the surroundings, resulting in a temperature decrease. The products have higher overall energy than the reactants, and energy must be supplied for the reaction to occur.
Reaction profiles illustrate the energy changes during a chemical reaction. The activation energy is the minimum energy required to initiate the reaction and break the bonds in the reactants.
Problem: Identify the exothermic and endothermic reactions in the following reaction profiles:
Solution:
During a chemical reaction, bonds in the reactants must be broken (absorbing energy), and new bonds in the products must form (releasing energy). The overall energy change depends on the difference between the energy absorbed for bond breaking and the energy released for bond forming.
Chemical reactions can be harnessed to generate electricity in chemical cells and fuel cells. These devices use redox reactions (electron transfer) to produce an electrical current.
For more information on chemical reactions and energy changes, refer to official exam board specifications and resources like BBC Bitesize.