Specific energy refers to the amount of energy stored in a given mass of a substance. It is often expressed in units like joules per kilogram (J/kg). This concept is important in fields like engineering and energy production, as it helps compare the energy potential of different fuels or materials. For example, gasoline has a higher specific energy than batteries, meaning it can store more energy per unit of weight. Understanding specific energy is crucial for optimizing energy use and improving efficiency. By knowing the specific energy of various sources, scientists and engineers can make informed decisions about which materials to use for transportation, power generation, and other applications. This knowledge ultimately contributes to more sustainable energy solutions.