Il profumo del caffè riempie la casa quando tutto è silenzioso.

del is a contraction of di (of) + il (the), so del caffè literally means “of the coffee.” In Italian, when you want to say “the smell of the coffee,” you need both the preposition and the article. Just di caffè would sound like “of coffee” without specifying “the” coffee, and it’s less natural here.

The accent on caffè serves two purposes:

1. It marks the stress on the last syllable.
2. It indicates an open /ɛ/ vowel sound, distinguishing it from a closed /e/.
   Without the accent, readers wouldn’t know where to place the stress or how to pronounce the vowel.

• profumo generally refers to a pleasant or fragrant smell (perfume, aroma).
• odore is more neutral, simply “odor” or “smell,” and can be good, bad or indifferent.
  Since coffee’s scent is usually enjoyable, profumo is the more idiomatic choice here.

riempie is the third-person singular present indicative of riempire (to fill). The present-tense pattern is:
• io riempio
• tu riempi
• lui/lei riempie
• noi riempiamo
• voi riempite
• loro riempiono

Italian -ire verbs split into two groups:

1. -isc- verbs (finire, capire, preferire…), which insert -isc- in io/tu/lui/lei and loro forms.
2. Non--isc- verbs (aprire, dormire, riempire…), which keep a regular stem.
   riempire belongs to the second group, so it conjugates without -isc-.

In Italian, singular countable nouns generally require an article. riempie casa would sound ungrammatical. You need la casa (“the house”). Omitting the article works only in some fixed expressions or after certain prepositions, but not here.

Yes, La casa si riempie di profumo is perfectly correct. Nuance:

• Il profumo … riempie la casa is an active construction focusing on the scent as the agent.
• La casa si riempie di profumo is a reflexive/passive style, emphasizing the house becoming filled.
  Both convey the same scene; the choice is stylistic.

Here tutto is a neuter singular pronoun meaning “everything.” Neuter pronouns in Italian take the masculine singular adjective form, so you get silenzioso, not a plural or feminine form.

• tutto è silenzioso uses silenzioso (adjective) to describe the state of everything.
• If you used the noun, you’d need a different structure, e.g. c’è silenzio in casa (“there is silence in the house”).
• in silenzio is an adverbial phrase meaning “quietly” or “in silence,” often describing how someone does something. Saying quando tutto è in silenzio is possible but shifts the feel; it’s slightly less direct than the adjective form.

Yes, you could say Il profumo del caffè riempie la casa mentre tutto è silenzioso.

• quando simply marks a point or period in time (“when”).
• mentre emphasizes two actions or states happening simultaneously (“while”).
  In practice, the nuance is subtle and both are acceptable.