A bunch of questions about ところ

Question

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.

Case 1

• 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。。。

Case 2

• 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。。。

Questions

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

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.

Answer 2

1. It is a noun. It has a meaning of "abstract place; scene; range". I used online Japanese-Japanese dictionary here: search for 抽象的な場所。場面。範囲。

2. No, they would all sound weird.

3. 食べているところなんです feels like "I'm at the moment of eating (something)", and 食べているんです means "I'm eating".

4. 出かけているところ is not between 出かけるところ and 出かけたところ. I noticed that in addition to leave house, 出かける can include the meaning of doing something (outside the house), although the weight is put mainly on the action of leaving house. Since it will sound weird that the action of "leaving house" is continuing, it will be interpreted as the meaning of "going out and doing something" when used as 出かけているところ. When used as 出かけたところ, it means the action of leaving house is just finished; I feel that, since the word 出かける's weight is on the action of leaving house, it is weird to specify the very ending scene of the followed action.

5. ところ is just a noun.