Final answer:
Performing a haircut, shattering a piece of glass, and blowing dry hair represent physical changes because they alter form or shape without changing the material's chemical composition.
Step-by-step explanation:
Performing a haircut, shattering a piece of glass, and performing a thermal style with a blow dryer are all examples of physical changes. These activities change the form or shape of the material, but they do not alter the chemical composition. For instance, when glass shatters, it breaks into smaller pieces, but the composition of the glass remains the same.
Similarly, cutting hair changes the length but not the chemical makeup of the hair strands. When using a blow dryer for thermal styling, heat changes the shape and style of the hair, but not its chemistry. This is opposed to chemical changes, which are transformations resulting in the creation of new substances, such as the reaction that occurs during a perm when chemicals change the hair's structure.