What Am I Riddles

Question: What force and strength cannot get through, I with a gentle touch can do, And many in the street would stand, Were I not a friend at hand.

Question: I'm a measurement of time.
But you'll find me on a map, not a clock.

What am I?

Question: Surrounded by green, surrounding white.
Inside is red, holding many black babies.

What is it?

Question: I can go up a chimney down but not down a chimney up?

What am I?

Question: When warm my house expands and when cold it contracts,
I am vital to a certain type of pact.

What am I?