Breakdown of Buntując się przeciwko rodzicom, nastolatek wyraża swoją nową tożsamość.
nowy
new
rodzice
the parents
swój
one's own
przeciwko
against
Questions & Answers about Buntując się przeciwko rodzicom, nastolatek wyraża swoją nową tożsamość.
Does buntując się just mean that the rebelling and expressing happen at the same time?
It means they happen at the same time, but it also has an explanatory function here. The contemporary adverbial participle (ending in -ąc) often explains how or why the main action happens. In this sentence, it shows the method: it is by rebelling that the teenager expresses his identity.
Why is the word for parents in the form rodzicom here?
The preposition przeciwko (against) strictly requires the dative case. Rodzicom is the dative plural form of rodzice.
Could we use jego instead of swoją to mean his new identity?
No, using jego here would mean he is expressing some other male's identity. Because the teenager is the subject of the sentence and the identity belongs to him, you must use the reflexive possessive pronoun swój. Here it takes the feminine accusative form swoją to match the noun it describes.
The word tożsamość ends in a consonant. Why does it take the feminine modifiers swoją nową?
Abstract nouns ending in the suffix -ość (like tożsamość, meaning identity) are feminine in Polish. As the direct object of wyraża, the phrase is in the accusative case. While feminine nouns ending in a consonant don't change their own ending in the accusative, any adjectives or pronouns attached to them must take the standard feminine accusative -ą ending.