There are two prepositional phrases in the sentence: "In the summertime" and "at the science museum."
The sentence "In the summertime, Hana works at the science museum as a tour guide" contains two prepositional phrases.
The first one is "In the summertime," and the second is "at the science museum."
Prepositional phrases begin with a preposition and end with a noun, pronoun, or noun phrase, which is called the object of the preposition.
In the first prepositional phrase, "In" is the preposition, and "the summertime" is the object.
In the second prepositional phrase, "at" is the preposition, and "the science museum" is the object.
These prepositional phrases provide additional information about the time (summertime) and the place (the science museum) related to Hana's work as a tour guide.
They help to add context and detail to the sentence, allowing the reader to visualize when and where Hana carries out her role as a tour guide.