Learn Hardcore Polish: Płonące ognisko ogrzewa ramiona dzieci. - The burning campfire warms the children’s shoulders.

a present active participle (imiesłów przymiotnikowy czynny),
used like an adjective,
agreeing with ognisko in:
- gender: neuter
- number: singular
- case: nominative

So płonące ognisko literally means the burning campfire / the campfire that is burning.

Why is it płonące ognisko and not płonie ognisko?

Both are correct Polish, but they play different roles in the sentence:

Płonące ognisko – burning campfire
- płonące acts as an adjective describing the noun ognisko.
- It is part of the subject phrase.
Płonie ognisko – the campfire is burning
- płonie is a finite verb (3rd person singular).
- It would typically be the main verb of a clause.

In your sentence, the main verb is ogrzewa, so the “burning” information has to be expressed as an adjective/participle, not as another main verb.
Płonące ognisko ogrzewa… = The burning campfire warms…

Why is it ognisko and not ogień if both can mean “fire”?

Polish distinguishes between several “fire” words:

ognisko – a campfire, bonfire, a specific fire you sit around outdoors.
ogień – fire in a more general sense (the element), or a flame, or “fire!” as in “Shoot!”.
płomień – a flame.

Here we clearly mean a campfire that children are sitting around, so ognisko is the natural choice.
Ogień ogrzewa ramiona dzieci would sound more like “The fire (in general) warms the children’s shoulders,” without the campfire image.

What tense and aspect is ogrzewa? How is it different from ogrzał or ogrzeje?

Ogrzewa is:

present tense
imperfective aspect
3rd person singular (he/she/it warms)

Aspect differences:

ogrzewa – is warming / warms (in general), focuses on the ongoing process or repeated action.
ogrzał – past tense, perfective: he/it warmed (and finished warming).
ogrzeje – future tense, perfective: he/it will warm (and complete the warming).

In context, Płonące ognisko ogrzewa… means the campfire is currently warming the children’s arms/shoulders.

Why ramiona, not ręce or ramiona dziecięce?

Body-part vocabulary nuances:

ręce – hands or sometimes arms (from shoulder to hand), but usually thought of as “hands”.
ramiona – shoulders / upper arms / arms (more the “upper limb” as a whole, neck-to-arm area).
ramiona dzieci here suggests the children’s arms/shoulders, the part that is being warmed when they sit near the fire.

You could say:

ogrzało im ręce – it warmed their hands
ogrzało ich ramiona – it warmed their arms/shoulders

Ramiona dzieci sounds a bit more literary or descriptive than ręce dzieci in this particular image.

What case is ramiona dzieci, and how does the grammar work there?

The structure is:

ramiona – accusative plural (direct object of ogrzewa)
dzieci – genitive plural, specifying whose arms/shoulders

So literally: “warms the arms of (the) children”.
Polish often uses:

[part of body in accusative] + [owner in genitive]
e.g. widzę oczy kota – I see the cat’s eyes (literally “the eyes of the cat”).

Here: ogrzewa ramiona dzieci – warms the children’s arms/shoulders.

How can I tell that dzieci is genitive, not nominative, since the form is the same?

The noun dzieci is irregular:

Nominative plural: dzieci – children (subject)
Genitive plural: dzieci – of (the) children
Dative plural: dzieciom
Accusative plural: dzieci
Instrumental plural: dziećmi
Locative plural: dziećiach (rare, often replaced by dziećmi in speech)

So the form dzieci itself is ambiguous; you know the case from context:

Dzieci śpią. – subject → nominative plural
Nie ma dzieci. – after nie ma → genitive plural
Ramiona dzieci – “arms of children” structure → dzieci must be genitive.

Here, because it depends on ramiona and means whose arms, it’s clearly genitive.

Why is the word order Płonące ognisko ogrzewa ramiona dzieci and not, for example, Ognisko płonące ogrzewa dziecięce ramiona?

Polish word order is fairly flexible, and both sentences are grammatical, but they sound different:

Płonące ognisko ogrzewa ramiona dzieci.
Neutral, descriptive: The burning campfire warms the children’s arms.
Ognisko płonące ogrzewa dziecięce ramiona.
More poetic/literary: dzięki przestawieniu participle and adding dziecięce (an adjective meaning “childlike/children’s”).

Basic rules:

Information tends to flow Subject – Verb – Object, like in English.
Descriptive participles like płonące usually come before the noun they modify.
Genitive owners (like dzieci) usually come after the noun they “own” (ramiona dzieci).

So the original sentence is a very standard and natural word order.

Could I say Płonące ognisko grzeje ramiona dzieci instead of ogrzewa?

Yes, but there’s a nuance:

grzać – to heat/warm in general; can be more casual and broad.
ogrzewać – to warm up, to make something warm; often used when something warms someone up, especially from cold.

In this context:

grzeje ramiona dzieci – warms the children’s arms
ogrzewa ramiona dzieci – warms up / keeps warm the children’s arms, with a bit more sense of comfort from the cold.

Both are correct; ogrzewa simply sounds a bit more “cosy by the fire.”

Is ognisko the subject or is ramiona dzieci the subject?

The subject is płonące ognisko.

It’s in nominative singular (neuter): ognisko.
The verb ogrzewa is 3rd person singular, agreeing with this subject.

Ramiona dzieci is the direct object (accusative), because it’s the thing being warmed.

So the sentence structure is:

[Subject] Płonące ognisko
[Verb] ogrzewa
[Object] ramiona dzieci

Why doesn’t Polish use a word for “the” or “the children’s” here, like English does?

Polish has no articles (a, an, the). Definiteness is expressed by:

context,
word order,
sometimes demonstratives like ten / ta / to (this, that).

So:

Płonące ognisko ogrzewa ramiona dzieci.
In context naturally means: “The burning campfire warms the children’s arms.”

If you really wanted to emphasize “these specific children,” you could add:

Płonące ognisko ogrzewa ramiona tych dzieci. – the arms of these children.

But normally, no article is needed; context takes care of it.