Function of Contrasts: Short Fiction Practice Test

In this excerpt, two siblings clean out a garage: “Caleb lifted the box labeled ‘SCHOOL’ and found his sister’s old notebooks, their covers bright with stickers and doodled hearts. In the corner, their mother’s suitcase sat plain and scuffed, the tag still looped through the handle like a question no one answered. Caleb set the notebooks down carefully, as if noise might wake the past.” What is the function of the contrast between notebooks “bright with stickers” and the suitcase “plain and scuffed”?

Consider the excerpt: “After the argument, Tessa washed the dishes with furious precision. The soap bubbles rose bright and fragile, catching the overhead light like tiny planets. In the living room, her partner’s silence sat on the couch thick as wet laundry, refusing to dry.” What is the function of the contrast between bubbles “bright and fragile” and silence “thick as wet laundry”?