Get Your Head Around These!

15 Points Per Correct Answer - No time limit  

1. I can be seen when it’s cold, but not when hot. You need me to live - take your last and you're not. Answer: (One Word)

2. If one=3, two=3, three=5, and four=4, what do five + six= ? Answer: (One Word or Number (not eleven))

3. I sound like a word of one letter, but I’m actually three. Look the same from both ends - I’m a palindrome you see. Answer: (One Word)

4. Take me from there, and I end up here. Answer: (What am I?)

5. Add a letter to one, place it with care. Use the right letter - it’s no longer there. Answer: (One Word)