What is a physical change?

A physical change is characterized by a transformation that occurs without altering the chemical composition of the substance involved. In this context, the fourth option accurately describes how physical changes primarily involve changes in state of matter, such as melting, freezing, boiling, or condensing, which can happen due to environmental influences like temperature and pressure changes.

When a substance undergoes a physical change, such as ice melting to water or water evaporating to steam, the individual molecules remain intact, even though they may rearrange themselves or change their positions relative to one another. This distinction is crucial in defining physical changes, as it emphasizes that the identity of the substance does not change, even while its form or state does.

The other options do not correctly define physical changes. The first option hints at molecular transformations, but this can be misleading as physical changes should not affect the substance's chemical makeup. The second option's statement about only occurring with an increase in temperature is inaccurate, as physical changes can occur with decreases in temperature as well. Lastly, the third option clearly refers to changes in chemical composition, which aligns with chemical changes rather than physical ones. Thus, the selection emphasizes the key aspect of physical changes relating to the state of matter and its responsiveness to environmental conditions.