Voy a recalentar la sopa en el microondas.

This is the very common Spanish future structure:

• ir + a + infinitive

So:

• voy = I go / I am going
• a = to
• recalentar = to reheat

Together, voy a recalentar literally looks like I go to reheat, but it actually means I’m going to reheat.

This is one of the most natural ways to talk about a near future action in everyday Spanish.

Recalentar means to reheat — to heat something again.

• calentar = to heat / warm up
• recalentar = to reheat

So if the soup has already been cooked and is now being warmed again, recalentar is the most precise choice.

In real life, though, Spanish speakers may also say calentar la sopa if the context already makes it obvious that they mean reheating.

The prefix re- often adds the idea of again.

So:

• calentar = to heat
• recalentar = to heat again / reheat

It works similarly to English prefixes in words like rewrite, reopen, or reheat.

Spanish often uses the definite article (el, la, los, las) in places where English might not.

So:

• la sopa = the soup

Even when English might say something like I’m going to reheat soup, Spanish often prefers la sopa, especially when talking about a specific soup already known in the situation.

Here, la sopa sounds natural because it refers to a particular soup.

En el microondas means in the microwave.

• en = in
• el microondas = the microwave

Spanish normally says en el microondas for heating something using a microwave.

A learner may expect something like to the microwave, but Spanish does not usually say voy a recalentar la sopa al microondas in this context. En el microondas is the standard choice because it focuses on where/how the soup is being reheated.

Because microondas is a masculine noun, even though it ends in -s.

You just have to learn it as:

• el microondas

This word is interesting because it comes from horno microondas (microwave oven), and in everyday use people often shorten it to simply microondas.

So you say:

• el microondas
• un microondas

not la microondas.

It is singular here.

Even though microondas ends in -s, in this sentence it means the microwave as one appliance:

• el microondas = the microwave

Spanish has some singular nouns that end in -s, so the ending alone does not always tell you whether a noun is plural.

Yes. That is also very natural.

The difference is:

• calentar = heat / warm up
• recalentar = reheat

If you want to be exact and emphasize that the soup was already hot before, use recalentar.
If you simply want to say you’re heating it, calentar is perfectly common too.

Because Spanish often leaves out subject pronouns when the verb already makes the subject clear.

• voy already tells us the subject is I

So:

• Voy a recalentar la sopa... = I’m going to reheat the soup...

Adding yo is possible, but usually unnecessary unless you want emphasis or contrast:

• Yo voy a recalentar la sopa, no tú.
  I’m going to reheat the soup, not you.

A simple pronunciation guide is:

boy ah reh-kah-len-TAR lah SOH-pah en el mee-kroh-ON-das

A few useful notes:

• v in voy sounds closer to a soft English b
• r in recalentar is a light tapped r
• the stress is on:
  • voy
  • rentar in recalentar
  • so in sopa
  • on in microondas

In Spain, the pronunciation of c before e/i can sound like the th in think, so some speakers may pronounce part of recalentar with that sound depending on the consonants involved elsewhere, but in this sentence the main thing to notice is the general rhythm and stress.

The stress is on on:

• mi-cro-ON-das

So it sounds like:

mee-kroh-ON-das

This is important because Spanish stress is very regular, and saying the stress in the wrong place can make the word sound unnatural.

Yes, if it is clear from context that la refers to la sopa.

You could say:

• Voy a recalentar la sopa en el microondas.
• Voy a recalentarla en el microondas.

Both are correct.

With ir a + infinitive, object pronouns can often go:

1. before the conjugated verb

   • La voy a recalentar en el microondas.

2. attached to the infinitive

   • Voy a recalentarla en el microondas.

Both are natural.

Yes, it works perfectly in Spain.

The wording is standard and natural in Spain:

• Voy a... for near future
• recalentar
• en el microondas

In other Spanish-speaking countries, the same sentence would usually also be understood without any problem. There may be small regional preferences in vocabulary or phrasing, but this sentence is broadly standard.