What Am I Riddles

Question: Round like a dishpan and smaller than a bathtub.But the ocean can't fill it.What is it?

Question: When you do not know what I am, then I am something. But when you know what I am, then I am nothing. What am I?

Question: I brighten your day but live in the shade.

What am I?

Question: I'm made up of 12 completely different letters but you can type me with just 1, what am I?

Question: I have a neck but no head, 2 arms but no hands, I go with you to school, I go with you to work. What Am I?