grammar - A bunch of questions about ところ

I think the word ところ in my questions have nothing to do with 所{ところ}. Please correct me if I am wrong. Let us consider the following sentences.

• これから食{た}べるところなんですが。。。


• 今食{た}べているところなんですが。。。


• 今食{た}べたところなんですが。。。

• これから出{で}かけるところなんですが。。。


• 今出{で}かけているところなんですが。。。


• 今出{で}かけたところなんですが。。。

1. Is ところ a noun?


2. Can 時 replace ところ in the above sentences?


3. What is the difference between 食べているところなんです and simply 食べているんです when answering 何をしているんですか？


4. 食べているところ in the first case means the action occurs between 食べるところ and 食べたところ. How about 出{で}かけているところ? Does it also occur between 出{で}かけるところ and 出{で}かけたところ? Does 出{で}かけているところ mean that the person is still in his/her house but preparing to go out?


5. Are there special examples in which ～ところ grammar is very crucial?

Answer

1. 
   

   In your examples, ところ is used as a 形式名詞 (formal noun). It grammatically is a noun, but can't stand alone and just works like converter between word classes. Think it as "the time" used for "when", or "the way" used for "how".

   
   


2. 
   

   No. ～する時 means "when ~". When you're asked "What are you doing?", your answer wouldn't be "When I'm eating."

   
   


3. 
   

   It depends on what you think they want is. 食べているところなんです answers "What are you doing (at this moment)?", while 食べているんです is for "What (kind of action) are you doing?"

   
   



4. 
   

   出かける means "leave home (or usual places)". However, 出かけている isn't "leaving home" but "away from home". It's because Japanese punctual verbs take ている form to mean "consequent" rather than "progressive".
   EDIT: In this case, 出かけた means "have (just) left home" while 出かけている "(in the state of being) away from home", or dead literally, "be having left home", if such English were to exist.

   
   


5. 
   

   ところ is a word fills up more than a whole column in my dictionary. It has a bunch of meanings each of them worth a question. Maybe you can ask one on more specific usage, or it could be too broad for a single post.