Good Riddles

Question: What word begins with letter H, but add it with W and it becomes another word yet pronounced just the same?

Question: When you're given one, you'll have either two or none?

Question: What are the next 3 words in the sequence: j,f,m,a,m,j,j,a,s_,_, and _?

Question: Silent yet deafening. Invisible, but you know it's there. It can either make you laugh or it can make you cry. What is it?

Question: Without me, nothing exists. What am I?