Learn Hardcore Russian: Рядом мы поставили маленькое ведро, чтобы сортировать бумагу и пластик. - Next to it we put a small bin in order to sort paper and plastic.

As an adverb = “nearby, next to it/there”
- This is how it’s used in the sentence:
  Рядом мы поставили маленькое ведро…
  → “(Right) nearby we put a small bucket…”
It doesn’t say explicitly what it’s next to; that’s understood from context (e.g. nearby the desk, the trash can, etc.).
As a preposition with с
- instrumental
:
- рядом с домом – “next to the house”
- рядом с нами – “next to us”

So рядом without с is completely normal when you just mean “nearby / next to it (in general)” without naming the object.

Why does the sentence start with Рядом and not with Мы?

Russian word order is more flexible than English. You can say both:

Рядом мы поставили маленькое ведро…
Мы поставили маленькое ведро рядом…

They are both grammatically correct and mean essentially the same thing. The difference is in what is being emphasized:

Рядом мы поставили…
Puts a bit more emphasis on where you put it: “Nearby we put a small bucket…”
Мы поставили маленькое ведро рядом…
Sounds more neutral, similar to English “We put a small bucket nearby.”

Starting the sentence with an adverb (place, time, etc.) is very common in Russian when you want to set the scene: Потом мы…, Сначала он…, Там стоял дом, Рядом мы поставили…

Why is it маленькое ведро and not маленький ведро?

Because ведро is neuter, not masculine.

ведро – neuter noun (you see this from its ending ‑о)
The adjective must agree with the noun in gender, number, and case.

Neuter singular adjective endings in the accusative (and nominative) are usually ‑ое / ‑ее:

маленькое ведро – “a small bucket”
большое окно – “a big window”
чистое море – “a clean sea”

Masculine singular would be маленький:

маленький стол – small table
маленький дом – small house

So маленький ведро is wrong because the adjective is masculine, but the noun is neuter.

What aspect and tense is поставили, and why not ставили?

Поставили is:

past tense
perfective aspect
1st person plural (“we”)

So мы поставили ≈ “we (have) put / we placed (and finished doing it).”

Ставить (imperfective) vs поставить (perfective):

ставить – to put, to be putting, to put regularly / repeatedly
(process or repeated action)
поставить – to put once, to place something as a completed act

Compare:

Мы ставили ведро рядом каждый день.
“We used to put the bucket nearby every day.” (repeated, habitual)
Мы поставили ведро рядом.
“We (once) put the bucket nearby.” (one completed action)

In your sentence it describes one specific completed action, so perfective поставили is natural.

Why поставили, not положили? Aren’t both “to put”?

Both can translate as “to put,” but they’re used differently:

поставить – to put something upright / standing (vertical position)
положить – to put something lying down (horizontal position)

Typical examples:

поставить стакан на стол – to put a glass on the table (it stands)
положить книгу на стол – to put a book on the table (it lies)

A ведро (bucket) is normally imagined standing upright, so you use поставить ведро.
Положить ведро would sound odd unless you very intentionally laid it on its side.

Why is there a comma before чтобы?

Чтобы сортировать бумагу и пластик is a subordinate clause of purpose (“in order to…”). In Russian, subordinate clauses are normally set off from the main clause by a comma.

Main clause:

Рядом мы поставили маленькое ведро – “We put a small bucket nearby”

Purpose clause:

чтобы сортировать бумагу и пластик – “in order to sort paper and plastic”

So you get:

Рядом мы поставили маленькое ведро, чтобы сортировать бумагу и пластик.

Whenever чтобы introduces a clause explaining why / for what purpose something was done, you put a comma before it.

Why is it чтобы сортировать, not чтобы мы сортировали?

Both are possible, but there is a nuance:

Чтобы + infinitive (your sentence)
- чтобы сортировать
  Very common in everyday speech for “in order to do (something).”
  It sounds slightly more neutral / general:
Мы поставили ведро, чтобы сортировать бумагу и пластик.
“We put the bucket there to sort paper and plastic.”
Чтобы + personal form (мы сортировали)
- чтобы мы сортировали
  This focuses more explicitly on who should do it:
Мы поставили ведро, чтобы мы сортировали бумагу и пластик.
“We put the bucket there so that we would sort paper and plastic.”

In most real-life contexts, the simpler чтобы сортировать is more natural unless you need to emphasize the subject (who is supposed to sort).

Why is сортировать in the imperfective, not something like отсортировать?

Imperfective сортировать describes the process / ongoing activity of sorting in general:

чтобы сортировать бумагу и пластик
“so that we can sort paper and plastic (as an ongoing practice)”

Perfective forms like отсортировать would stress a single completed sorting:

чтобы отсортировать бумагу и пластик
“in order to sort (them) out once / completely (this batch).”

Here the bucket is for regular, repeated sorting as a habit, not for one-time sorting of a specific pile, so imperfective сортировать is the natural choice.

Why are бумагу and пластик in that form? What case is this?

They are both in the accusative case, because they are the direct objects of the verb сортировать (“to sort”).

сортировать что? – “to sort what?”
- бумагу (from nominative бумага, feminine)
- пластик (nominative and accusative singular are identical)

Forms:

бумага (nom.) → бумагу (acc.)
пластик (nom.) → пластик (acc.; for inanimate masculine nouns, nominative = accusative)

So:

сортировать бумагу и пластик – “to sort paper and plastic”

Why isn’t there any word for “a” or “the” before маленькое ведро?

Russian has no articles (no “a/an” or “the”). Whether you mean “a small bucket” or “the small bucket” is determined only by context, not by a special word.

Мы поставили маленькое ведро. Can be:
- “We put a small bucket (there).”
- “We put the small bucket (there).”

If you really need to stress that it is some bucket, not a specific known one, you can add words like:

одно маленькое ведро – one small bucket
какое‑то маленькое ведро – some small bucket

But usually context makes it clear enough.

Could we move рядом to another position, like in English?

Yes. All of these are possible, with slightly different emphasis:

Рядом мы поставили маленькое ведро, чтобы сортировать бумагу и пластик.
Focus on the place: “Nearby, we put a small bucket…”
Мы рядом поставили маленькое ведро, чтобы сортировать бумагу и пластик.
Also possible; emphasizes that we put it nearby (not somewhere else).
Мы поставили рядом маленькое ведро, чтобы сортировать бумагу и пластик.
Very natural; close to English “We put a small bucket nearby…”
Мы поставили маленькое ведро рядом, чтобы сортировать бумагу и пластик.
Also natural; рядом comes right after the direct object.

All versions are grammatical; Russian uses word order for nuance and emphasis more than for basic grammar.

How do you pronounce and stress the main words in this sentence?

Stress (´) marks the stressed syllable; ё is always stressed:

Ря́дом – RYA-dom
мы – my (short “i”)
поста́вили – pa-STÁ-vi-li (stress on ста)
ма́ленькое – MÁ-len’-ka-ye
ведро́ – ve-DRÓ
чтобы – SHTO-by (the first syllable is like что)
сортирова́ть – sar-ti-ra-VÁT’ (stress on the last syllable)
бума́гу – bu-MÁ-gu
пла́стик – PLÁ-stik

Full sentence, marking stress:

Ря́дом мы постави́ли ма́ленькое ведро́, что́бы сортирова́ть бума́гу и пла́стик.