Answer:
a. The mothballs gradually vaporize in a closet. Physical change
b. Hydrofluoric acid attacks glass, and is used to etch calibrations marks on glass laboratory utensils. Chemical change
c. A French chef making a sauce with brandy is able to burn of the alcohol from the brandy leaving just the brandy flavoring. Chemical change
d. Chemistry majors sometimes et holes in the cotton jeans they wear to lab, because of acid spills. Chemical change
e. A piece of egg boiled in water for 20 minutes. Chemical change
Explanation:
In a physical change, there is no change in the chemical composition of the substance, the change is only on the physical properties. For example, state changes (a).
In a chemical change instead, usually there is a combination of two or more substances that combine to form a new one different from the originals. For example, chemical reactions like combustion (c) or protein denaturalization (e). The attacking of hydrofluoric acid to glass (b) or the acid pill attacking cotton are chemical reactions too (d).
