In scientific experiments, what is the significance of achieving temperatures at or near absolute zero?

Achieving temperatures at or near absolute zero is significant primarily because it drastically reduces the kinetic energy of particles. As temperatures approach absolute zero, the atomic and molecular motion slows down significantly, leading to a near cessation of thermal motion. This allows scientists to study quantum mechanical effects that are not observable at higher temperatures, such as superconductivity and superfluidity. It enables the creation of states of matter that are not achievable at standard conditions, providing insight into the fundamental behaviors of particles.

The other options, while they touch on interesting phenomena related to low temperatures, do not accurately capture the primary significance of approaching absolute zero. Changes in chemical properties can occur at lower temperatures, but they are not the main focus of studies involving absolute zero. Increased thermal expansion is associated with heating rather than cooling, and freezing all states of matter is not practically feasible as some states, like Bose-Einstein condensates, exist under such conditions, but they are distinct from the concept of freezing. Therefore, reducing the kinetic energy of particles is the most accurate and relevant aspect when discussing absolute zero in scientific contexts.