Energy is the ability to do work. In other words, if Ben needed 1000 joules of energy to move a box 5 meters across the floor it would make no difference whether he had 1000 joules of thermal energy or the same amount of mechanical energy. He could still do the work required to get the job done

While energy is conserved in terms of total magnitude, the ability to do useful work depends on the quality and form of energy, described by thermodynamics. Thermal energy cannot be fully converted into mechanical work due to entropy constraints, making the statement false regarding interchangeable utility for specific mechanical tasks.