What does an increase in atomic weight suggest about a substance's entropy?

When considering the relationship between atomic weight and entropy, it's important to understand the concept of entropy in thermodynamics. Entropy is a measure of the disorder or randomness of a system, and it tends to increase with the complexity of a substance and the number of microstates available to it.

As atomic weight increases, substances often become more complex in terms of molecular structure and the variety of configurations they can adopt. Heavier atoms can participate in more intricate bonding arrangements and allow for greater vibrational, rotational, and translational motion. This increased atomic mass generally leads to a higher number of accessible microstates, resulting in higher entropy.

For example, larger molecules (which often contain heavier atoms) can have more rotational and vibrational modes compared to lighter molecules. This means they have an increased capacity to be in different configurations or states, contributing to an overall increase in the system's entropy.

Thus, an increase in atomic weight typically correlates with an increase in entropy, making the option indicating that entropy will likely increase the most appropriate choice. This relationship underscores the fundamental concepts in thermodynamics regarding how complexity and atomic structure influence a system's disorder.