Learn Hardcore Russian: На большой перемене студентка обычно идёт в соседний кабинет пить чай. - During the big break a female student usually goes to the neighboring classroom to drink tea.

Feminine noun ending in -а / -я → prepositional -е:
перемена → перемене
Short-form adjective feminine большая → большой in prepositional:
большая → большой

So на большой перемене literally means “on (at) the big break” in the prepositional case after на in its “location/time” meaning.

Why is the preposition на used with перемене, not в?

With time expressions, Russian often uses на where English uses at / during. Some nouns are just idiomatically fixed with на:

на уроке – in class, during the lesson
на перемене – at break, during the break
на работе – at work
на обеде – at lunch (lunch break)

So на перемене is a standard collocation. В перемене is not used in this meaning.

What exactly does большая перемена mean? Is it just “big break”?

Literally it is “big/large break,” but culturally it means the longer recess in a school or university schedule.

In many schools there are several short breaks and one longer one; the longer one is большая перемена. So it’s a specific, longer break rather than just “a break that is physically big.”

Why is it студентка, not студент?

Russian has grammatical forms that mark the gender of people:

студент – a (male) student
студентка – a (female) student

The sentence is explicitly talking about a female student, so студентка is used. If the student were male, the sentence would be:

На большой перемене студент обычно идёт в соседний кабинет пить чай.

Why is it идёт and not ходит here?

Russian motion verbs distinguish:

идти → идёт – going now / this time / in a single, concrete instance, or movement in one direction.
ходить → ходит – habitual or multi-directional movement: “goes (there and back, in general).”

You might expect ходит because of обычно (“usually”), but both are possible with a nuance:

обычно ходит – emphasizes the habit: she generally goes there (a regular practice).
обычно идёт – feels like: “When the big break comes, she (each time) goes there,” focusing more on each instance as it happens.

The original sentence is natural; it presents each occurrence of the big break and what she does then.

Can I say На большой перемене студентка обычно ходит в соседний кабинет пить чай? Is that correct?

Yes, that is also correct and maybe even more expected for some speakers with обычно.

Nuance:

обычно идёт – more “every time the break starts, she (then) goes…”
обычно ходит – more strongly “she has this habit of going…”

Both work; the difference is subtle and often not crucial in everyday speech.

What case is в соседний кабинет, and why does it use that form?

This is accusative singular masculine after в with a direction (motion into / to something).

Nominative: соседний кабинет
Accusative (direction): в соседний кабинет

Explanation:

кабинет – masculine inanimate noun; nominative and accusative are the same in form: кабинет.
соседний – adjective; masculine accusative singular for inanimate nouns = same as nominative: соседний.

So идёт в соседний кабинет = “goes to the neighboring room/classroom.”

Does кабинет here mean “cabinet” (a piece of furniture) or something else?

In this context, кабинет means a room, usually:

a classroom
an office
a specific subject room (e.g. кабинет физики – the physics room)

It does not mean a furniture cabinet. For the piece of furniture, Russian would typically say шкаф.

What does соседний mean exactly, and how is it different from соседский?

соседний means adjacent / next / neighboring in position.
соседний кабинет = “the room next door / the room next to ours.”
соседский means belonging to a neighbor (possessive).
соседская собака = “the neighbor’s dog.”

So:

соседний кабинет – a physically neighboring room.
соседский кабинет – would suggest “the neighbor’s room” (odd in this context).

Why is the infinitive пить used here? Why not a finite verb?

After verbs of motion and some other verbs, Russian often uses the bare infinitive to express purpose:

идёт (куда?) в соседний кабинет (зачем?) пить чай
“goes to the next room to drink tea.”

This is a common pattern:

идти смотреть фильм – to go watch a movie
поехать отдыхать – to go rest / go on vacation

So пить is infinitive showing purpose of going.

Could we use чтобы here, like идёт в соседний кабинет, чтобы пить чай?

Yes, that is also grammatically correct:

На большой перемене студентка обычно идёт в соседний кабинет, чтобы пить чай.

However:

The simple infinitive after a verb of motion is more concise and very natural.
With чтобы, the sentence feels a bit more explicit, slightly more formal or explanatory: “in order to drink tea.”

Both are fine; the original version is more streamlined Russian.

Why is it пить чай and not выпить чай?

Both are possible, but they differ in aspect and nuance:

пить чай – imperfective, emphasizes the process / activity:
“to drink tea” (spend time drinking tea, have tea as an activity).
выпить чай – perfective, emphasizes the completion / result:
“to drink (up) some tea,” “to have a cup of tea (and finish it).”

In the context of what she usually does during the break, пить чай fits well because it presents tea drinking as her typical activity in that time slot, not focusing on the finished result.

Can обычно be placed in other positions, like at the beginning of the sentence?

Yes, обычно is fairly flexible. All of these are possible, with small nuances:

На большой перемене студентка обычно идёт в соседний кабинет пить чай.
Neutral; обычно directly modifies идёт.
Обычно на большой перемене студентка идёт в соседний кабинет пить чай.
Slightly stronger emphasis on “as a rule, during the big break…”
Студентка обычно на большой перемене идёт в соседний кабинет пить чай.
Emphasizes that it’s the big break in particular when this “usually” happens.

Word order mostly affects emphasis, not basic meaning. The original order is very natural.