Answer:
Without this, H2O would just be 2O
I am someone you don't know. Who am i?
A twiggy home
I'm the start of eternity and the end of space. There are two of me in heaven and one in hell.
It's tough as nails, Or soft as snow. People use it for their rink, Some just put in their drink.
What is 9 added to any number ending in 1