Question

read the passage and then answer the question.
a phase transition occurs when a substance is transformed from one state of matter into another due to changes in temperature or pressure. some phase transitions, like melting, freezing, evaporation, and condensation, are commonly observed in everyday life. for example, when water freezes to form ice, it undergoes a phase transition from a liquid state to a solid state; and when it evaporates, it undergoes a phase transition from liquid to gas. other phase transitions, however, are less common. one such change is sublimation, a process exemplified by the behavior of dry ice—frozen carbon dioxide commonly used to keep packaged items cold and dry during shipping. when dry ice is left at room temperature, the solid carbon dioxide changes to carbon dioxide gas without melting into a liquid first.
what is the meaning of sublimation as used in the passage?
a physical process in which solid carbon dioxide melts
a physical process in which carbon dioxide becomes dry ice
a physical process in which a solid changes directly to a gas
a physical process in which a gas changes directly to solid

Explanation:

The passage states that when dry ice (solid carbon dioxide) is left at room temperature, it changes to carbon dioxide gas without melting into a liquid first. This directly describes a solid changing directly to a gas.

Answer:

a physical process in which a solid changes directly to a gas