Se o xampu acabar, minha irmã usa o meu condicionador e depois liga o secador.

Because after se meaning if, Portuguese often uses the future subjunctive when the condition refers to a possible future situation.

So:

• Se o xampu acabar = If the shampoo runs out
• not Se o xampu acaba in this kind of future condition

This is a very common pattern in Portuguese:

• Se eu tiver tempo... = If I have time...
• Se ela chegar cedo... = If she arrives early...
• Se o xampu acabar... = If the shampoo runs out...

A useful thing to notice is that for many -ar verbs, the future subjunctive looks exactly like the infinitive, so acabar here is not the plain infinitive in meaning, even though it looks the same.

Both usa and liga are in the present indicative, third person singular:

• usa = (she) uses
• liga = (she) turns on

Portuguese often uses the present tense to describe a habit, a general rule, or something that typically happens.

So this sentence sounds like:

• If the shampoo runs out, my sister uses my conditioner and then turns on the hair dryer.

It suggests a repeated or typical action.

If you wanted to make it sound more explicitly future-oriented, Portuguese could also say something like:

• Se o xampu acabar, minha irmã vai usar o meu condicionador...
• Se o xampu acabar, minha irmã usará o meu condicionador...

But the present tense is very natural here.

Here acabar means to run out or to be used up, not just to finish in a general sense.

So:

• O xampu acabou = The shampoo ran out
• Se o xampu acabar = If the shampoo runs out

Portuguese uses acabar a lot in this sense with products, supplies, food, money, and so on.

Examples:

• O café acabou. = The coffee ran out.
• A água acabou. = The water ran out.
• Meu dinheiro acabou. = I ran out of money.

Because Se o xampu acabar is an introductory conditional clause.

In Portuguese, when a subordinate clause like this comes first, it is normally separated from the main clause by a comma:

• Se o xampu acabar, minha irmã usa o meu condicionador...

This is similar to English:

• If the shampoo runs out, my sister uses my conditioner...

If the order were reversed, the comma would often disappear:

• Minha irmã usa o meu condicionador se o xampu acabar.

Portuguese uses definite articles much more often than English.

So where English might say:

• shampoo
• hair dryer

Portuguese very naturally says:

• o xampu
• o secador

In this sentence, the article helps show that we are talking about a specific, understood item: the shampoo, the dryer.

This is extremely common in Portuguese and often sounds more natural than leaving the article out.

In Brazilian Portuguese, it is very common to use a definite article before a possessive:

• o meu condicionador = my conditioner

You can also hear:

• meu condicionador

Both are possible in Brazilian Portuguese, but o meu condicionador is very natural and common.

A quick summary:

• o meu / a minha = very common in Brazil
• meu / minha without the article = also possible

So this is not a different meaning; it is mainly a matter of normal usage and style.

Yes. In Brazilian Portuguese, ligar is a very common verb for turning on a device or appliance.

So:

• ligar o secador = to turn on the hair dryer
• ligar a luz = to turn on the light
• ligar a televisão = to turn on the TV

The opposite is:

• desligar = to turn off

So:

• desligar o secador = to turn off the hair dryer

Be careful, though: ligar can also mean to call on the phone, depending on context.

In this context, yes.

Secador literally means dryer, but in everyday use it often refers to a hair dryer, especially in a bathroom or grooming context.

If needed, you can be more explicit:

• secador de cabelo = hair dryer

But just secador is very natural when the meaning is obvious.

Yes. Xampu is the standard Portuguese spelling in Brazil.

It comes from the English word shampoo, but Portuguese adapted the spelling to match Portuguese pronunciation.

So you may see:

• xampu in standard Portuguese writing
• shampoo sometimes on packaging, brand labels, or in less adapted spelling

For learners, xampu is the best form to know as standard Brazilian Portuguese.

Portuguese often drops subject pronouns like eu, ela, nós when the verb already makes the subject clear.

But here the subject is a full noun phrase:

• minha irmã

It is included because the speaker wants to say specifically my sister.

If the subject had already been established, Portuguese could use a pronoun or even leave it implied in some contexts:

• Se o xampu acabar, ela usa o meu condicionador...
• In a very clear context, even the pronoun might be omitted in some styles

But in this sentence, saying minha irmã is the clearest and most natural way to identify who does the action.

Because both verbs are conjugated in the third person singular, which can mean:

• he
• she
• it
• sometimes you in formal address, depending on context

Here the subject is minha irmã, which is she, so:

• minha irmã usa = my sister uses
• minha irmã liga = my sister turns on

The base verbs are:

• usar = to use
• ligar = to turn on / to call

Their present-tense forms here are:

• usa
• liga

You might hear something like that, but acabar is the more natural choice for running out of shampoo.

Compare the ideas:

• acabar = to run out / to be used up
• terminar = to finish / to end

With products like shampoo, soap, toothpaste, or coffee, acabar is usually the most idiomatic verb.

So:

• Se o xampu acabar sounds very natural.
• Se o xampu terminar is less typical in this context.

For a learner, acabar is the one to remember here.