NOUN CLAUSE

A noun clause is a dependent clause and cannot stand alone as a sentence.  It must be connected to an independent clause, a main clause. A noun clause has its own subject and verb. It can begin with a question word. It can begin with if or whether. And it can begin with that. 

a) Noun clauses with question words: 

The following question words can be used to introduce a noun clause: when, where, why, how, who, whom, what, which, whose. 

Example: 

Answer this question using 'I don't know...'

Where does Maria live?

I don't know -------------.

It is incorrect to say, "I don't know where does she live."

Notice that "does she live" is a question form.  Noun clauses cannot be in question form; it has to be a statement.

"I don't know where she lives" is the correct answer.

Example: these questions using I don't know... 

·         How old is Kate?

 I don't know how old she is.

·         Where did Juan go?

I don't know where he went.

·         Why did Maria leave?

I don't know why she left.

·         What did she say?

I don't know what she said.

·         When is she going to leave?

I don't know when she is going to leave.

·         What country is Maria from?

I don't know what country she is from.

·         What is that girl's name? 

I don't know what her name is.

Noun clauses with who, what, whose + be:

A noun or pronoun that follows main verb 'be' in a question comes in front of 'be' in a noun clause. 

Example:
--> Who is that boy? I don't know who that boy is.

--> Whose pen is this? I don't know whose pen this is.

A prepositional phrase does not come in front of 'be' in a noun clause. 

Example:
--> Who is in the office? I don't know who is in the office.

--> Whose pen is on the desk? I don't know whose pen is on the desk.

Notice that usual word order is not used when the question word is the subject of the question as in 'who' and 'what'.  In this case, the word order in the noun clause is the same as the word order in question.

Be sure to complete the exercises in the assignments.

b) Noun clauses, which begin with if or whether:

When a yes/no question is changed to a noun clause, if is usually used to introduce the clause.  

Example:
--> Is Maria at home?

               I don't know if Maria is at home.

--> Does this bus go to Los Angeles?

               I don't know if this bus goes to Los Angeles.

--> Did Juan go to Mexico?

               I wonder if Juan went to Mexico.

Frequently, speakers may add 'or not'.  This comes at the end of the noun clause in sentences with 'if' and immediately after 'whether' in sentences with 'whether'.

Example:
--> I don't know if Maria is at home or not. 

--> I don't know whether or not Maria is at home.

Notice that we cannot use 'or not' immediately after 'if'.

c) Noun clauses which begin with that: 

A noun clause can be introduced by the word 'that'.

--> I think that Ms. Weiss is a good teacher.

In the sentence above, 'Ms. Weiss is a good teacher' is a noun clause. It is the object of the verb 'think'.

That clauses are frequently used as the object of verbs which express mental activity. Here are some common verbs followed by 'that clauses'. 

Assume that   believe that  discover that dream that

Guess that    hear that     hope that     know that

Learn that    notice that   predict that  prove that   

Realize that  suppose that  suspect that  think that

There are many more verbs that can be followed by "that" clause.

Example:

·         I feel that she will do well on the test.

·         I wonder if she is coming to the part.

·         You are lucky that won the lottery.

·         It is a fact that Mr. Lopez is a good teacher.

·         I doubt that she will come today.

·         I am worried that they won't win the game.

·         I don't know when she will come.

·         I regret that she failed the test.

·         I don't know if she lives in New York or not.

·         I am amazed that we made it to the airport on time.

source: 

http://www.testyourenglish.net/english-online/subjects/nouncl1.html

http://www.english-grammar-revolution.com/noun-clauses.html