Se o micro-ondas parar de funcionar, vou esquentar a sopa no fogão.

Because after se meaning if, Portuguese often uses the future subjunctive when talking about a possible future situation.

So:

• Se o micro-ondas parar... = If the microwave stops...

With regular -ar verbs, the future subjunctive form can look exactly like the infinitive, so parar here is correct.

Compare:

• ele para = it stops / he stops in the present
• se ele parar = if it/he stops in the future

This is a very common pattern in Portuguese:

• Se chover, fico em casa.
• Se você quiser, eu ajudo.

Because parar de + infinitive is the normal way to say stop doing something.

So:

• parar de funcionar = to stop working
• literally: to stop functioning

Other examples:

• parar de falar = stop talking
• parar de comer açúcar = stop eating sugar

You usually cannot drop the de here.

Vou + infinitive is the very common everyday way to talk about the future in Brazilian Portuguese.

So:

• vou esquentar = I’m going to heat up
• esquentarei = I will heat up

Both are correct, but vou esquentar sounds more natural in normal spoken Brazilian Portuguese.

In conversation, Brazilians often prefer:

• vou fazer
• vou comprar
• vou ligar
• vou esquentar

instead of the simple future forms.

Yes. Se o micro-ondas parar de funcionar, esquentarei a sopa no fogão is grammatically correct.

But it sounds more formal or written. In everyday Brazilian Portuguese, vou esquentar is usually more natural.

So the difference is mostly one of style and frequency, not meaning.

Yes. You can say:

Vou esquentar a sopa no fogão se o micro-ondas parar de funcionar.

That means the same thing.

A useful punctuation note:

• If the se clause comes first, a comma is normal:
  • Se o micro-ondas parar de funcionar, vou esquentar...
• If it comes second, the comma is usually omitted:
  • Vou esquentar... se o micro-ondas parar de funcionar.

Because no is a contraction of:

• em + o = no

So:

• no fogão = on the stove
• literally: in the stove, but in Portuguese this is the normal form

Similar contractions:

• na = em + a
• nos = em + os
• nas = em + as

Examples:

• no carro
• na mesa
• nos livros
• nas caixas

Because fogão means stove / cooker, while forno means oven.

So:

• esquentar a sopa no fogão = heat the soup on the stove
• assar no forno = bake in the oven

English sometimes uses stove and oven loosely, but Portuguese keeps them more clearly separated.

Yes, micro-ondas is masculine, so it normally takes o:

• o micro-ondas
• um micro-ondas

In this sentence, it means the microwave oven.

Also, Portuguese very often uses articles where English might skip them, so o micro-ondas sounds natural.

Because micro-ondas is one singular noun, even though it ends in -s.

This confuses many learners. The word comes from micro-ondas in the sense of microwaves, but as a compound noun it can refer to one appliance:

• o micro-ondas está quebrado = singular
• os micro-ondas estão quebrados = plural

So you have to look at the article and the rest of the sentence, not just the final -s.

Portuguese uses definite articles more often than English does.

So a sopa is very natural here, especially if it refers to a specific soup already known in the situation.

Compare:

• Vou esquentar a sopa. = I’m going to heat up the soup.
• Vou fazer sopa. = I’m going to make soup.

In Portuguese, using the article often sounds more complete and natural.

They are close, but esquentar is usually more common in everyday speech for things like food and drinks.

• esquentar a sopa = very natural
• aquecer a sopa = also correct, but a bit more formal or technical in some contexts

You will hear esquentar a lot in daily Brazilian Portuguese:

• esquentar o café
• esquentar a comida
• esquentar no micro-ondas

One extra note: esquentar can also have other meanings in different contexts, like to heat up emotionally or physically, but here it is simply about warming food.

Because the sentence starts with a conditional clause:

• Se o micro-ondas parar de funcionar = the condition
• vou esquentar a sopa no fogão = the main result

When that if clause comes first, Portuguese normally separates it with a comma.

So this is standard punctuation, just like in English:

• If the microwave stops working, I’ll heat the soup on the stove.

The ending -ão is a nasal sound that English does not really have.

Fogão is approximately:

• fo-GOWN if you want a rough English-style hint

But that is only approximate, because the ão is nasal, not a normal English own sound.

A few pronunciation tips:

• Stress falls on the last syllable: fo-GÃO
• The g sounds like g in go
• The ão is nasal, with air partly going through the nose

This -ão ending is very common in Portuguese:

• pão
• mão
• televisão
• fogão

It is worth practicing because it appears in many everyday words.