Tencerenin kapağını açınca sıcak buhar çıktı.

Tencerenin is tencere + -nin, the genitive ending.

Here it means of the pot.

So:

• tencere = pot
• tencerenin = of the pot / the pot’s

This is used because the next noun, kapağını, is something that belongs to the pot.

Because kapağını contains several things at once:

• the noun kapak = lid
• consonant softening: kapak → kapağ-
• -ı = its (3rd person possessive)
• -nı = accusative ending after a possessive form

So kapağını means its lid or, in this sentence, the lid (of the pot) as a specific object.

Turkish often marks both sides of this kind of possession:

• tencerenin = of the pot
• kapağı / kapağını = its lid / the lid

This is a very common Turkish structure.

In English, we say:

• the pot’s lid

In Turkish, possession is usually shown on both nouns:

• possessor: tencerenin = of the pot
• possessed item: kapağını = its lid / the lid

This double marking is normal in Turkish and sounds natural.

This is due to consonant softening.

Some Turkish words ending in p, ç, t, k soften when a vowel-starting suffix is added.
So:

• kapak
• kapağı
• kapağını

Here k becomes ğ.

This is a very common pattern in Turkish.

Açınca comes from açmak = to open.

The ending -ınca / -ince often means:

• when
• once
• upon
• after

So açınca means:

• when (someone) opened
• upon opening

In this sentence, it connects the two actions:

• opening the lid
• steam coming out

Turkish often leaves the subject unstated if it is clear from context or not important.

So açınca by itself does not tell you exactly who opened it.
Depending on context, it could mean:

• when I opened
• when he/she opened
• when they opened
• more generally when the lid was opened in loose English translation, though the Turkish form here is active

The sentence focuses on what happened next, not on who did the opening.

Çıktı is the definite past tense of çıkmak.

Breakdown:

• çık- = come out / go out
• -tı = past tense
• 3rd person singular is unmarked here

So çıktı means:

• came out
• went out

In this sentence: hot steam came out.

Because the meaning come out / go out is already built into the verb çıkmak.

So:

• çıkmak = to go out / come out / exit
• çıktı = came out / went out

English often uses a verb + particle, but Turkish often expresses that idea with a single verb.

This is normal Turkish word order.

A very natural way to organize it is:

1. Tencerenin kapağını açınca = when the pot’s lid was opened / when (someone) opened the pot’s lid
2. sıcak buhar = hot steam
3. çıktı = came out

Turkish often puts:

• time/background information first
• the main verb at the end

So the sentence structure is very typical.

In Turkish, adjectives do not agree with the noun.

So:

• sıcak buhar = hot steam
• sıcak su = hot water
• sıcak yemekler = hot foods

The adjective sıcak stays the same.
It does not change for number, gender, or case.

Yes — the best English translation depends on context.

Açınca is flexible. In natural English, it might be rendered as:

• when (someone) opened the lid
• upon opening the lid
• after opening the lid

All of these can work here. The core idea is that the steam came out as a result of or immediately after opening the lid.

Yes. For example, you might also hear forms like:

• Tencerenin kapağını açtığında sıcak buhar çıktı.
• Tencerenin kapağı açılınca sıcak buhar çıktı.

These are similar, but not identical.

• açınca is compact and very natural
• açtığında also means when (someone) opened
• açılınca means when it was opened / when it opened, using a passive/intransitive form

So the original sentence is a normal, natural way to say it.