According to the 1st Law of Thermodynamics, what can be said about energy?

The principle embodied in the 1st Law of Thermodynamics, often referred to as the law of energy conservation, states that energy cannot be created or destroyed, but can only change forms or be transferred from one system to another. This means that the total energy within a closed system remains constant over time, although it can transition between kinetic, potential, thermal, and other forms of energy.

Option C accurately reflects this understanding by asserting that energy is constant and can only be transferred. This is fundamental in various fields, including physics and engineering, as it establishes the baseline for understanding how energy systems operate, predicting energy flow, and analyzing processes such as heating, cooling, and work.

In contrast, the other options misinterpret or misapply the principles of the 1st Law. The idea that energy can be created in an open system contradicts the conservation principle. Similarly, suggesting that energy can be destroyed during a reaction conflicts with the notion that energy is always conserved. Lastly, the concept that energy can increase indefinitely in a closed system ignores the law's assertion that energy remains constant, further illustrating why option C is the correct interpretation of the 1st Law of Thermodynamics.