Final answer:
The appositive phrase in the given sentence is 'A tireless artist', providing additional insight into the character of Chris Evans. Appositive phrases clarify or add detail to the preceding noun, similarly to using specific details in art or writing to emphasize particular aspects or concepts.
Step-by-step explanation:
The words that make up the appositive phrase in the sentence 'A tireless artist, Chris Evans offered to paint the portrait of each student in his class.' are 'A tireless artist'. This phrase is giving us additional information about Chris Evans. An appositive phrase adds explanatory or clarifying information to the noun that precedes it, which can offer insight into the subject's identity or character, and is set off by commas. In writing, such details help create a fuller image of the subject, much like vivid colors in a painting bring attention to certain aspects of the artwork.
Appositives can be used powerfully in sentences to provide more context, similar to how an image or word cloud might emphasize specific concepts like 'fairness' or 'opportunity', or how adding specific details can change the sentiment embodied by words like 'apple' or 'blue'. In the same vein, when setting off appositives with dashes, they emphasize the information within the appositive phrase, enhancing the impact on the reader.