What Am I Riddles

Question: At night they come without being fetched, and by day they are lost without being stolen.

What are they?

Question: I'm light as a feather, yet the strongest man can't hold me for more than 5 minutes. What am I?

Question: I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter.

What am I?

Question: You use a knife to slice my head and weep beside me when I am dead.

What am I?

Question: Give me food, and I will live. Give me water, and I will die. What am I?