Depois do jantar, ficou um pouco de arroz na panela.

Because Portuguese normally contracts de + o into do.

So:

• de o jantar → do jantar

This kind of contraction is extremely common:

• de + a → da
• de + os → dos
• de + as → das

In depois do jantar, the phrase means after dinner literally after the dinner.

Ficar has several meanings, and one very common one is to remain / to be left.

In this sentence, ficou um pouco de arroz na panela means that some rice remained in the pan after dinner.

So here ficar is not really to stay in the physical sense of a person staying somewhere. It is more like:

• There remained...
• There was still...
• ...was left

This is a very natural use in Portuguese.

Examples:

• Ficou comida na geladeira.
  There was food left in the fridge.

• Ficaram alguns problemas.
  Some problems remained.

Because the grammatical subject is um pouco de arroz, and that whole expression is treated as singular.

The core idea is um pouco = a little bit / a small amount, which is singular.

So:

• Ficou um pouco de arroz... = singular
• Ficaram alguns grãos... = plural

Compare:

• Ficou um pouco de café.
• Ficaram alguns copos na mesa.

Even though arroz refers to many grains in real life, grammatically it is an uncountable noun here, like rice in English.

Portuguese often puts the verb before the subject when introducing something that existed, remained, appeared, happened, etc.

So ficou um pouco de arroz na panela sounds natural because it presents new information: some rice was left.

A more direct subject-first version is also possible:

• Um pouco de arroz ficou na panela.

That is grammatical, but it may sound a bit more focused on um pouco de arroz itself. The original version is very natural in everyday Brazilian Portuguese.

This is similar to how English often uses there was:

• There was a little rice left in the pan.

Portuguese does not need a word like there here.

It can correspond to either a little rice or some rice, depending on context.

Um pouco de literally means a little bit of or some.

So:

• um pouco de arroz = a little rice / a little bit of rice / some rice

It usually suggests a small amount, but not necessarily an extremely tiny amount.

Also notice the structure:

• um pouco de + noun

Examples:

• um pouco de água = a little water
• um pouco de tempo = a little time
• um pouco de dinheiro = some money / a little money

Because um pouco de arroz is talking about some rice in a general quantity sense, not some of the rice as a specific previously identified rice.

Compare:

• um pouco de arroz = some rice / a little rice
• um pouco do arroz = some of the rice

So if you say:

• Ficou um pouco de arroz na panela.
  A little rice was left in the pan.

But:

• Ficou um pouco do arroz na panela.
  Some of the rice was left in the pan.

The second version sounds more specific, as if both speaker and listener already know which rice is being talked about.

Because na is the contraction of em + a.

So:

• em a panela → na panela

This means in the pan.

Very common contractions:

• em + o → no
• em + a → na
• em + os → nos
• em + as → nas

Examples:

• no quarto = in the room
• na mesa = on the table
• nos livros = in the books
• nas caixas = in the boxes

Ficou is the preterite of ficar.

The preterite is used because the sentence refers to a completed situation in the past: after dinner, the result was that some rice remained in the pan.

So this is a finished past event/state.

• ficou = remained / was left

If you used the imperfect, ficava, it would suggest a repeated or ongoing past situation, which does not fit as well here.

Compare:

• Depois do jantar, ficou um pouco de arroz na panela.
  After dinner, a little rice was left in the pan.
  one completed situation

• Depois do jantar, sempre ficava um pouco de arroz na panela.
  After dinner, there was always a little rice left in the pan.
  repeated habit in the past

Yes, and in many situations sobrou would sound very natural.

• Depois do jantar, sobrou um pouco de arroz na panela.

Sobrar specifically means to be left over / to remain as excess.

The difference is subtle:

• ficou = remained / was left
• sobrou = was left over

So sobrou can sound a bit more explicit about leftovers.
Ficou is slightly broader and can simply describe what remained.

In everyday Brazilian Portuguese, both can work here.

No. Portuguese allows some flexibility.

The original sentence:

• Depois do jantar, ficou um pouco de arroz na panela.

Other possible orders include:

• Ficou um pouco de arroz na panela depois do jantar.
• Um pouco de arroz ficou na panela depois do jantar.

The original version is very natural because it sets the time first, then gives the main information.

Putting Depois do jantar first is common when you want to frame the whole sentence with when it happened.

Yes.

In Portuguese, jantar can be:

• a verb: to have dinner
• a noun: dinner

In this sentence, jantar is a noun:

• depois do jantar = after dinner / after the dinner meal

Examples:

• Vamos jantar às oito.
  We are going to have dinner at eight.
  verb

• O jantar foi ótimo.
  Dinner was great.
  noun

Here, the article in do jantar helps show that it is functioning as a noun.

Not exactly.

With há, the verb is impersonal:

• Há arroz na panela.
  There is rice in the pan.

In that kind of sentence, há does not agree with a subject in the normal way.

But in ficou um pouco de arroz na panela, um pouco de arroz is the grammatical subject, and the verb agrees with it:

• ficou because um pouco is singular

So this sentence is not fully impersonal; it just uses a verb-first order that feels a bit like English there was.