can you answer these?

Question by prchica_gurl:

#1
My life can be measured in hours;
I serve by being devoured.
Thin, I am quick; fat, I am slow.
Wind is my foe.
What am I?

#2
Lighter than what I’m made of,
More of me is hidden than is seen.
What am I?

#3
To unravel me
You need a key.
No key that was made by locksmith’s hand,
But a key that only I will understand.
What am I?

#4
I give you a group of three. One is sitting down and will never get up. The second eats as much as is given to him, yet is always hungry. The third goes away and never returns. What are they?

#5
Whoever makes it, tells it not. Whoever takes it, knows it not. Whoever knows it, wants it not. What is it?
answer all correctly wins!!