Learn Hardcore Portuguese (Portugal): Troca a esponja velha da cozinha; não limpa bem a tábua. - Change the old kitchen sponge; it doesn’t clean the cutting board well.

In this context it’s the affirmative imperative, telling someone to replace the sponge. It addresses the informal singular “you” (tu). It could also be read as present indicative “he/she replaces,” but the semicolon and the following comment make the command reading the natural one in Portuguese.

What’s the difference between troca and troque?

Troca is the affirmative imperative for tu (informal singular).
Troque is the affirmative imperative for você (formal singular) and also for the polite/indirect style. In Portugal, people tend to use tu with friends/family: Troca a esponja…. With someone you don’t know well or want to be polite with, use Troque a esponja….

How do I include “it” (the sponge) as a pronoun in the command?

In European Portuguese, affirmative imperatives take the object pronoun after the verb, with a hyphen:

Troca-a (replace it) — feminine “it” because esponja is feminine. If the command were negative, the pronoun would go before the verb and you’d switch to the subjunctive form:
Não a troques (don’t replace it) — for tu.
Não a troque (don’t replace it) — for você.

Why is the adjective after the noun in a esponja velha? Could I say a velha esponja?

Portuguese usually places adjectives after the noun. A esponja velha is neutral (“the old/worn sponge”). Putting it before the noun (a velha esponja) is possible but can sound more subjective or stylistic; with some adjectives, position can subtly change meaning (e.g., um velho amigo = long-time friend, vs um amigo velho = a friend who is old). Here, post-nominal velha is the most natural choice.

What exactly does da cozinha mean? Is it “of the kitchen,” “from the kitchen,” or “kitchen (type)”?

da cozinha = “of the kitchen/the kitchen’s,” identifying which sponge we’re talking about (the one for the kitchen).
If you want to express type/material more generically, you can use de: esponja de cozinha = “kitchen sponge” (as a category).
If you want location, use na cozinha = “in the kitchen.”
So the sentence refers to the specific kitchen sponge, not just any sponge located in the kitchen.

Why is da used and not de a?

Portuguese contracts prepositions with articles. de + a = da; de + o = do; de + as = das; de + os = dos.
Here, it’s de + a cozinha → da cozinha.

Who’s the subject of não limpa in the second clause? Why is it missing?

Portuguese is a “pro-drop” language: subject pronouns are often omitted when context makes them clear. Here, the understood subject is “it,” i.e., the sponge previously mentioned. You could say Ela não limpa bem a tábua, but it’s not necessary.

Could I say limpa mal a tábua instead of não limpa bem a tábua?

Yes. Limpa mal a tábua is idiomatic and concise (“cleans the board poorly”). Não limpa bem a tábua sounds a bit softer/less blunt. Both are fine.

Why is it bem and not bom in não limpa bem?

bem is an adverb (“well”), used to modify verbs. bom/boa is an adjective (“good”), used with nouns. You clean “well” (verb), so it’s limpa bem, not “limpa bom”.

Is limpa here a verb or an adjective?

A verb. limpa is the 3rd person singular of limpar (“to clean”). As an adjective, limpa would mean “clean” (feminine), but then it would have to agree with a noun: e.g., a tábua está limpa (“the board is clean”). In the sentence, limpa takes a direct object (a tábua), so it’s clearly a verb.

What does tábua refer to here? Should I say tábua de cortar?

On its own, tábua literally means “board/plank.” In kitchen contexts, a tábua is commonly understood as the cutting board. If you want to be explicit, say a tábua de cortar or a tábua de cozinha. All are natural in Portugal.

Is the semicolon (;) necessary? Could I use a period?

A period would be perfectly fine: two related sentences. The semicolon signals a tight link between the command and the justification. Avoid a comma here; in Portuguese, you generally don’t join two full clauses with just a comma.

How do I pronounce the tricky parts like tábua, cozinha, and não?

tábua: stress on the first syllable; the “bua” is like “bwa” → roughly “TAH-bwa”.
cozinha: the “nh” is like the “ny” in “canyon” → “koo-ZEE-nya” (European PT often devoices the final “a” a bit).
não: nasal vowel; think “now” but nasalized → “now̃” (one syllable).
troca: open “o,” tapped r → “TROH-kah”.
esponja: “j” like the “s” in “measure” → “ish-PON-zhah”.
limpa: nasalized “im” → “LEEN-pah” (more precisely, [ˈlĩpɐ]).

How can I soften the command?

Add politeness: Por favor, troca a esponja… (informal) / Por favor, troque a esponja… (polite).
Use a request: Podes trocar a esponja…? (informal) / Pode trocar a esponja…? (polite).
Even softer: Será que podes/pode trocar a esponja…?

If I wanted to address more than one person, what changes?

Use vocês forms:

Affirmative imperative: Troquem a esponja…
Negative: Não a troquem… Similarly, the present statement would be Não limpam bem a tábua (“you [pl.] don’t clean the board well”) if the subject were “you.”

Do I need the article before tábua? Could I say não limpa bem tábua?

Keep the definite article in standard usage: a tábua. Dropping it sounds unnatural here. Portuguese tends to use articles more than English with singular count nouns.

Can I replace the noun with a pronoun in the second clause?

Yes. If the subject is the sponge and the object is the board:

Full: Não limpa bem a tábua.
With object pronoun: Não a limpa bem. (“It doesn’t clean it well.”) If you also name the subject explicitly: Ela não a limpa bem.