a. Moth balls gradually vaporize in a closet: Physical Change
Explanation: The moth balls change from a solid state to a gas as they vaporize, but their chemical composition remains the same. This is a classic example of a physical change where the form of the substance changes, but not its identity.
b. Hydrofluoric acid attacks glass: Chemical Change
Explanation: When hydrofluoric acid comes into contact with glass, it reacts with the silica in the glass, leading to the formation of new compounds. This reaction indicates a transformation of the material’s chemical structure, classifying it as a chemical change.
c. A chef making a sauce with brandy is able to burn off the alcohol from the brandy, leaving just the brandy flavoring: Chemical Change
Explanation: The process of burning off the alcohol is a chemical change because it involves combustion, resulting in new substances being formed (water and carbon dioxide, along with other compounds). The alcohol no longer exists in its original form, making this a chemical transformation.