useless trivia: What Word Means: To Fade?

Questions

What's Krypton's state at standard temperature & pressure?

What's the apparent gap between Saturn's A & B rings called?

What's the general name for germ fighting drugs such as penicillin & streptomycin?

What's the largest & most powerful of the American cats?

What's the most effective insulator brick, fibreglass or wood?