What happens to the entropy of a system when energy is added?

When energy is added to a system, it typically increases the number of microstates associated with that system, leading to an increase in entropy. Entropy is a measure of the disorder or randomness of a system, and adding energy usually allows the particles within that system to move more freely and occupy more possible arrangements.

For example, in a solid that is heated, the added energy causes its atoms to vibrate more vigorously, which increases the disorder of the arrangement of those atoms. In liquids and gases, the added energy can enable more molecular motion and thus a greater variety of configurations, further contributing to an increase in entropy.

This relationship aligns with the second law of thermodynamics, which states that the total entropy of an isolated system can never decrease over time. Therefore, when energy is added to a system, the expectation is that entropy increases as the system becomes more disordered and the molecules have more freedom to explore different states.