때, (다/라)면, -을 하다

[carsont]

I have a few questions that have been bothering me for a while:

1. When is it necessary, or advisable, to break up -하다 verbs, e.g. turning 일하다 into 일을 하다? The only case given in my textbook was when negating with 안 or 못. I'm guessing that it's also necessary when modifying the noun, e.g. 많은 일을 하다 -- is that right? Is it done in cases when neither the noun nor 하다 are being modified?

2. Which verb modifiers can be used with 때? I seem to remember having read that it's limited to 을 for non-past events and (었/았)을 for past events, but I can't find where I read that, so I might be mistaken. I think I may have seen -ㄴ/은 and -는 being used also. Are they? And can 던 or 었/았던 ever be used with 때?

3. How does one choose between using just -(으)면 versus -다면 or -라면? I understand that -면 is somewhere between English "if" and "when", and I gather that -다면 is more hypothetical, closer to the "if" end of that spectrum... is there any distinction apart from that? Are there any cases in which one must be used over the other?

Thanks in advance if anyone can explain any of these more clearly!

[padeca07]

1) As far as when to separate 하다 verbs the answer is a little tricky as not all 하다 verbs can be separated as such. 일을 하다 is a little more grammatically correct literally meaning "to do work" where as 일하다 means "to work" but there is really no difference between the two unless, like you stated before, you are modifying the type of work making it more specific like: 회사 일 (company work) 회사 일을 하다 "to do company work"
Another situation when you separate the two is with the introduction of (안, 못, 열심히, 많이, etc...)
공부를 열심히 하다 would be the correct way to say this
열심히 공부하다 is technically incorrect although people will know what you mean

2) 때 is most commonly used two ways, with a verb or noun, to express "the time when"
noun + 때
저녁때 dinner time
verb stem + (으)ㄹ 때
저녁을 먹을 때 when I eat dinner
(ㄴ,은,는,던) are used to modify verbs giving the verbs an adjective quality

3) You are pretty much correct (으)면 is just "if" and is most likely the one you should be using where as 다면 is very hypothetical and is often used in conjunction with 만약
for example: 만약에 타임 머신 (time machine) 있다면... - Hypothetically speaking, if you had a time machine...
-라면 has the same meaning as (으)면 but is used with nouns. The 라 being used in the "reporting" sense where noun 이다 becomes noun 이라
피터입니다 - I'm Peter
피터라고 합니다 - I'm Peter/ I'm called Peter
피터라면... - If I were Peter...
피터라도... - Even if I were Peter...

hope this helps