An exothermic reaction is exemplified by the combustion of methane, while an endothermic reaction is represented by the melting of ice.

Exothermic reactions are characterized by the release of energy in the form of heat, light, or sound. A prime example is the combustion of methane, which is a highly exothermic process. In this reaction, methane ($\text{CH}_4$) reacts with oxygen ($\text{O}_2$) to produce carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$), releasing a substantial amount of heat in the process. This reaction is not only utilized in power generation but also provides the heat and light produced by gas stoves.

In contrast, endothermic reactions absorb energy from their surroundings. A notable example is the melting of ice, which requires energy to break the hydrogen bonds between water molecules, facilitating the transition from a solid to a liquid state. This energy is typically absorbed as heat, which explains why ice cubes placed in a warm environment eventually melt. Other examples of endothermic reactions include the evaporation of water and the thermal decomposition of calcium carbonate ($\text{CaCO}_3$).

Understanding the distinction between exothermic and endothermic reactions is crucial across various scientific disciplines, including chemistry, biology, and physics. By analyzing the energy changes that occur throughout a reaction, scientists can gain valuable insights into the underlying chemical processes, paving the way for the development of new technologies and materials.