What does the first law of thermodynamics state?

The first law of thermodynamics states that energy cannot be created or destroyed, but can change from one form to another. This principle is founded on the conservation of energy, which means that the total energy in an isolated system remains constant. When energy is transformed — for example, from chemical energy in fuel to thermal energy when burned — the amount of energy present in the system does not increase or decrease; it simply shifts between forms.

Understanding this law is crucial in thermodynamics and engineering because it emphasizes that while energy can be transferred and transformed, the total energy balance in any system remains unchanged. This concept helps engineers design systems that adhere to energy conservation principles, ensuring efficiency and functionality across various applications, from heating systems to engines. The option highlighting energy conservation in a closed system reflects a fundamental aspect of physical laws, reinforcing that while energy may alter in its state, the total quantity remains constant.