Final answer:
The energy level of reactants is higher than that of products in an exothermic reaction, indicating energy release, while in an endothermic reaction, the energy level of products is higher, reflecting energy absorption. All reactions require overcoming activation energy.
Step-by-step explanation:
When comparing the energy levels of reactants and products in a chemical reaction, it largely depends on whether the reaction is exothermic or endothermic. In an exothermic reaction, the energy level of the reactants is higher than that of the products. This is because exothermic reactions release energy, typically in the form of heat, to the surroundings. Energy diagrams for these reactions typically show a downward slope from the reactants to the products.
In contrast, an endothermic reaction requires an input of energy, meaning the energy level of the reactants is lower than that of the products. This is because the system absorbs energy from its surroundings to drive the reaction forward. The energy diagrams for endothermic reactions are represented as an uphill slope from the reactants to the products.
It is important to note that all chemical reactions, whether exothermic or endothermic, require an initial input of energy to overcome the activation energy barrier, which is the energy required to initiate the reaction. Once this barrier is overcome, the reaction proceeds, releasing or absorbing energy as it moves towards the products.