لو كان الحليب في الثلاجة، لصنعت أمي قهوة لنا.

لو usually introduces a counterfactual or unreal condition in MSA Arabic. It often corresponds to English if ... were / had ... would ....

So in this sentence, لو كان الحليب في الثلاجة، لصنعت أمي قهوة لنا suggests that the milk is not in the fridge, and therefore the coffee was not made.

This is different from a more open, real possibility, where Arabic might use إذا or sometimes إن instead.

That is a very common question. In Arabic, after لو for unreal conditions, the verb is often put in the past form, even when the meaning in English is closer to were or would be rather than a simple past.

So:

• لو كان الحليب في الثلاجة literally looks like if the milk was in the fridge
• but the real meaning is if the milk were in the fridge

This is a normal Arabic pattern. The past form here does not simply mean past time; it helps express an unreal or contrary-to-fact condition.

Because الحليب is a masculine singular noun.

The verb كان agrees with its subject in gender and number, so:

• كان الحليب = the milk was / were
• If the subject were feminine singular, you would use كانت

For example:

• لو كانت القهوة جاهزة... = If the coffee were ready...

Since الحليب is masculine, كان is correct.

This لـ is often called لام الجواب or the lām of the apodosis/response. It commonly appears in the main clause after لو to mark the result of the condition.

So the structure is:

• لو ... ، ل...

In this sentence:

• لو كان الحليب في الثلاجة
• لصنعت أمي قهوة لنا

This لـ helps signal the would have / would part of the meaning.

In English, we use would. In Arabic, one common way to show that idea in this structure is with لو plus a past verb in the condition, and often لـ plus a past verb in the result.

For the same reason as كان: in this kind of unreal conditional, Arabic often uses past verb forms in both parts of the sentence.

So:

• لصنعت أمي قهوة لنا

literally looks like my mother made coffee for us, but in this structure it means:

• my mother would make coffee for us
• or in some contexts would have made coffee for us

The exact English translation depends on context, but the Arabic grammar is normal and natural.

Arabic often prefers verb–subject order, especially in neutral written style.

So:

• صنعت أمي قهوة لنا = My mother made/would make coffee for us

This is very natural in MSA.

You could also say:

• أمي صنعت قهوة لنا

but that feels more like My mother made coffee for us, possibly with a bit more emphasis on my mother.

So in your sentence, صنعت أمي is simply the normal, straightforward word order.

Because the sentence means coffee in a general sense, not the specific coffee.

• قهوة = coffee / some coffee / a coffee
• القهوة = the coffee

Here the speaker is talking about making coffee for the group, not referring to a previously identified, specific coffee. So قهوة is the natural choice.

لنا means for us.

It is made of:

• لـ = for / to
• نا = us

So:

• قهوة لنا = coffee for us

Putting it at the end is very natural in Arabic. The phrase tells you who the coffee would be for.

Yes. في is the normal preposition for in.

So:

• في الثلاجة = in the fridge

Also, الثلاجة has الـ because it means the fridge, not just a fridge.

So the phrase is built very simply:

• في = in
• الثلاجة = the fridge

Without more context, Arabic لو + past ... ل + past can cover both kinds of unreal condition, and English chooses between them depending on context.

This sentence could be understood as:

• a present unreal idea: If the milk were in the fridge, my mother would make coffee for us
• or a past unreal idea: If the milk had been in the fridge, my mother would have made coffee for us

Very often, context tells you which one is meant.

If the speaker is talking about the current situation, the first English version is more natural. If they are talking about a missed situation in the past, the second works better.

Not if you want the same meaning.

• لو suggests an unreal / contrary-to-fact condition.
• إذا usually introduces a real, expected, or possible condition.

So compare:

• لو كان الحليب في الثلاجة، لصنعت أمي قهوة لنا
  = the milk is apparently not in the fridge

• إذا كان الحليب في الثلاجة، فستصنع أمي قهوة لنا
  = if the milk is in the fridge, my mother will make coffee for us

That second sentence sounds like a real possibility, not a hypothetical contrary-to-fact one.

Yes, in full formal grammar there are case endings, but in normal writing they are usually not written.

A fully vocalized version would show something like:

• لو كان الحليبُ في الثلّاجةِ، لَصَنَعَتْ أُمِّي قهوةً لنا

Some points a learner might notice:

• الحليبُ would be nominative as the subject/name of كان
• الثلّاجةِ is genitive after في
• قهوةً is accusative as the object of صنعت

But in ordinary Arabic text, these endings are usually omitted, so learners mainly focus on the word order and structure unless they are studying formal grammar in detail.