kodomo ga atui nabe ni sawarisou datta node, haha ha sugu tomemasita.

Because 子供 is the subject of 触りそうだった.

In this sentence, the child is the one who was about to touch the hot pot, so が marks the doer of that action/state.

• 子供が触りそうだった = The child looked like they were about to touch it

Using が here is very natural because it identifies who was in that situation.

Because 熱い is an い-adjective, and い-adjectives directly modify nouns.

So:

• 熱い鍋 = a hot pot

You do not add な after an い-adjective.

Compare:

• 熱い鍋 = hot pot
• 静かな部屋 = quiet room

Here, 静か is a な-adjective, so it needs な, but 熱い does not.

Because the verb 触る commonly uses に for the thing that is touched.

So:

• 鍋に触る = to touch the pot

This can feel a little surprising to English speakers, because English uses a direct object: touch the pot. But in Japanese, 触る often marks the target with に.

Examples:

• 犬に触る = touch the dog
• 壁に触る = touch the wall

So 熱い鍋に触りそうだった means was about to touch the hot pot.

触りそうだった means looked like he/she was about to touch or seemed likely to touch.

It is built like this:

• 触る → verb stem 触り
• そう = looks like / seems about to
• だった = past form

So:

• 触りそう = seems about to touch
• 触りそうだった = seemed about to touch / was about to touch

In this sentence, it does not mean the child actually touched the pot. It means the child was on the verge of doing so.

そうだった is the plain past form.

This sentence is in plain style overall:

• だった
• ので
• 止めました is polite, but the sentence mixes plain and polite in a way that is common enough in learner materials and everyday use.

The key point is that そう here behaves like a な-adjective-type expression, so it can take:

• そうだ = seems about to...
• そうだった = seemed about to...

The past is used because the speaker is describing what the situation was at that time, before the mother stopped the child.

It means was about to touch / looked like he was going to touch, not was touching.

That is an important difference.

• 触っていた = was touching
• 触りそうだった = looked like was about to touch

So the child had not necessarily touched the pot yet. The mother noticed the danger and stopped the child in time.

Both ので and から can mean because, but ので is usually softer and a bit more explanatory.

Here:

• 子供が熱い鍋に触りそうだったので
  = Because the child looked like they were about to touch the hot pot...

Compared with から, ので often sounds:

• a little more neutral
• a little more gentle
• a little more like giving a reason or explanation

So it fits well in a sentence describing why the mother acted.

Because 母 is the topic of the second clause.

The sentence has two parts:

1. 子供が熱い鍋に触りそうだったので
2. 母はすぐ止めました

In the second part, 母は introduces the mother as the person being talked about in that clause.

So the structure is roughly:

• Since the child was about to touch the hot pot, as for the mother, she immediately stopped him/her.

Using は here helps shift the focus to what the mother did in response.

The object is omitted because it is understood from context.

止める means to stop someone/something. Here, the mother most naturally stopped the child from touching the pot.

So the full idea is something like:

• 母は（子供を）すぐ止めました
• The mother immediately stopped the child

Japanese often leaves out objects when they are obvious.

So even though 子供を is not stated, listeners naturally understand it.

Because すぐ is an adverb, and adverbs often come before the verb they modify.

So:

• 母はすぐ止めました = The mother stopped him/her immediately

This placement is very normal in Japanese.

You could think of it as:

• 母は = as for the mother
• すぐ = immediately
• 止めました = stopped

Because 母 is commonly used when referring to one’s own mother in narration or explanation, especially from a more neutral outside perspective.

Very roughly:

• 母 = my/the mother, neutral/narrative style
• お母さん = mom / mother, more directly address-like or family-oriented

In a sentence like this, 母 sounds like standard written narration:

• 母はすぐ止めました = The mother immediately stopped him/her

If this were a child speaking casually about their own mom, お母さん might also be possible in a different context.

It is grammatically ambiguous. 子供 can mean:

• a child
• children

In this sentence, the meaning is most naturally a child, because the action sounds like one specific child reaching toward the pot. But Japanese nouns usually do not mark singular vs. plural unless the context makes it necessary.

So:

• 子供が could mean the child or the children
• context tells you which is intended

Here, the most likely reading is the child.

The sentence follows normal Japanese structure, with the reason first and the main action second:

• 子供が熱い鍋に触りそうだったので、母はすぐ止めました。

Breakdown:

• 子供が = the child
• 熱い鍋に = the hot pot
• 触りそうだった = looked about to touch
• ので = because
• 母は = the mother
• すぐ = immediately
• 止めました = stopped

So the overall flow is:

Because the child looked like they were about to touch the hot pot, the mother immediately stopped them.

This is very typical Japanese clause order: reason/situation first, main result second.