Learn Hardcore Japanese: natu ha senpuuki wo tukatte heya wo suzusiku site kara syukudai wo simasu. - In summer, I cool the room with a fan before doing my homework.

A（time）に B = “B at/on A (one occasion)”.
- 夏に日本へ行きます。 – “I’ll go to Japan in summer (this coming summer).”
Aは B with a time word often means “whenever it’s A / as for that time in general”.
- 夏は暑いです。 – “(In general) summer is hot.”

In this sentence we’re talking about a habitual action during the summer season, so 夏は is natural: “In summer, (I) …”.

You could say 夏に if you were talking about a specific summer event, but for a general seasonal habit, 夏は is more natural. You can also say 夏には to combine time (に) and topic/emphasis (は): 夏には扇風機を使って… (a bit more emphatic: “In summer (in particular), …”).

Why are there two を particles (扇風機を, 部屋を)? Can a sentence have more than one を?

Yes, a sentence can have more than one を. Each を marks the direct object of a verb or verb phrase.

扇風機を使って – 扇風機 is the object of 使って (the て-form of 使う, “to use”).
部屋を涼しくして – 部屋 is the object of 涼しくして (from 涼しくする, “to make (something) cool”).

So structurally you have:

[扇風機を使って] – “using a fan,”
[部屋を涼しくして] – “making the room cool,”
それから [宿題をします] – “and then do homework.”

Each verb or verb phrase takes its own object, so two を are perfectly fine.

Why is it 扇風機を使って and not 扇風機で使って or something with で?

With 使う, the thing you use is the direct object, so it normally takes を, not で.

扇風機を使う – “to use a fan.”
パソコンを使う – “to use a computer.”

で often marks:

Means/instrument with other verbs:
- ナイフで切る – “cut with a knife.”
- バスで行く – “go by bus.”
Location of an action:
- 教室で勉強する – “study in the classroom.”

But 使う itself means “to use (something),” so the thing used is simply marked with を. 扇風機で使う would sound like “use (something) by means of a fan,” which is not what we want.

What exactly does 部屋を涼しくして mean? How does this pattern work?

部屋を涼しくして comes from the pattern:

[Noun] を [adjective‑く] する
= “to make [Noun] [adjective].”

Here:

部屋 – “room” (object)
涼しい – “cool” (adjective)
涼しく – adverbial/“-く” form of 涼しい
する – “to make / to do”

So:

部屋を涼しくする – “to make the room cool.”

The て-form of する is して, giving 涼しくして:

部屋を涼しくして – “(after) making the room cool,” or “while making the room cool.”

In the full sentence, that て-form connects to から (“after … and then …”), so the nuance is: “(I) use a fan, make the room cool, and after that, (I) do homework.”

Why is the adjective 涼しい changed to 涼しく here?

涼しい is an い-adjective. When you use an い-adjective before する in the pattern Nを Adj-くする (“make N Adj”), you change ～い to ～く:

高い → 高くする – “make (it) high/expensive.”
静か（な） → 静かにする – “make it quiet” (な-adjectives use *に instead of く*).
涼しい → 涼しくする – “make (it) cool.”

So 涼しくして is just the て-form of 涼しくする (“to make [something] cool”).

What’s the difference between 涼しい, 寒い, and 冷たい?

These three are easy to mix up:

涼しい: “pleasantly cool” (air/temperature, usually positive)
- 今日は涼しいですね。 – “It’s nice and cool today.”
寒い: “cold” (air/temperature, usually uncomfortably cold)
- 冬はとても寒いです。 – “Winter is very cold.”
冷たい: “cold to the touch / emotionally cold”
- 冷たい水 – “cold water.”
- 彼は冷たい人だ。 – “He is a cold (unfeeling) person.”

In your sentence, 涼しくする is natural because you want your room pleasantly cool, not freezing or just physically cold to the touch.

What does ～てから (as in してから) mean exactly?

Vてから V2 means:

“After doing V, (then) do V2.”

It describes sequence: action 1 is completed, then action 2 happens.

In this sentence:

扇風機を使って部屋を涼しくして – use a fan and make the room cool,
から宿題をします – after that, do homework.

So the structure is:

[First: use fan & cool the room] てから [Next: do homework].

It implies the homework comes after the room has been cooled.

Could you use 前に instead of てから, like 宿題をする前に? Is the nuance different?

You can say something like:

宿題をする前に、扇風機を使って部屋を涼しくします。
– “Before doing homework, I use a fan and cool the room.”

The overall meaning is similar (cool room first, then homework), but:

Vてから V2 tends to emphasize “finish V, and then do V2” in sequence.
V2 前に V emphasizes “V happens before V2”, more from the perspective of V2.

In everyday conversation, both patterns can be used here; てから feels a bit more like you’re saying “once the cooling is done, I then do my homework.”

Why is the last verb 宿題をします in the polite ます-form instead of a plain form like する?

します is the polite form of する. Japanese has two main levels here:

Plain form (dictionary form): する, 行く, 食べる
Polite form (ます-form): します, 行きます, 食べます

The sentence as written is in polite style, so the main verb is 宿題をします. In polite style, all the conjugated verbs normally match that level; here:

使って, 涼しくして are て-forms, which are neutral in politeness.
The final verb します determines the overall politeness.

If you were speaking casually to a close friend, you might say:

夏は扇風機を使って部屋を涼しくしてから宿題をする。

There is no “I” in the Japanese sentence. How do we know who is doing the action?

Japanese often omits the subject when it’s clear from context. In English we must say “I” or “you,” but in Japanese it’s usually obvious from the situation:

Talking about your own routine → the subject is assumed to be “I.”
Talking to a friend about their habits → the subject might be “you.”

So:

夏は扇風機を使って部屋を涼しくしてから宿題をします。

in context would generally be understood as:

“In summer, I use a fan to cool my room and then do my homework.”

If you really want to show the subject explicitly, you can say:

私は夏は扇風機を使って部屋を涼しくしてから宿題をします。

Could the order be 部屋を涼しくして扇風機を使ってから宿題をします? How flexible is the word order?

Japanese word order is somewhat flexible, but not completely free. The basic rule is that the main verb comes at the end. Inside the sentence, phrases in て-form can sometimes be reordered, but it can sound unnatural or change nuance.

扇風機を使って部屋を涼しくしてから宿題をします。
– “(I) use a fan, (I) make the room cool, and then do homework.”
This flows logically.
部屋を涼しくして扇風機を使ってから宿題をします。
Grammatically possible, but odd in meaning: it sounds like you first make the room cool (by some unknown method), then use a fan, then do homework. The sequence becomes confusing.

Because using the fan is the means by which you cool the room, the natural order is:

[扇風機を使って] → [部屋を涼しくして] → [宿題をします].

So yes, word order has some flexibility, but cause/effect and time sequence still matter for naturalness.

Why 宿題をします instead of just 宿題します or 勉強します?

宿題 = “homework.”
する / します = “to do.”
宿題をする / 宿題をします = “to do homework.”

宿題する (without を) exists in casual speech, especially among younger speakers, but the standard/neutral form is 宿題をする.

勉強します means “to study (in general),” which is slightly different:

宿題をします。 – “I do my homework.” (Specific task assigned.)
勉強します。 – “I study.” (Broader, not necessarily assigned homework.)

In a school context where you specifically do your homework, 宿題をします is the most precise.

Could you replace 扇風機 with エアコン? Would the grammar change?

You can replace 扇風機 (fan) with エアコン (air conditioner) without changing the grammar:

夏はエアコンを使って部屋を涼しくしてから宿題をします。

Both 扇風機 and エアコン are just nouns, and 使う still takes them with を. The only change is the type of device used to cool the room. The structure and particles stay the same.