Final answer:
The cracks forming in a sidewalk during winter are an example of a physical change.
Step-by-step explanation:
The cracks forming in a sidewalk during winter are true an example of a physical change. Physical changes involve a change in the form or physical properties of a substance without altering its chemical composition. In this case, the water in the soil freezes and expands, causing the sidewalk to crack. However, the chemical composition of the water remains the same.