Riddle

What starts with T, ends with T, and has T inside it? I can be bigger than you but weigh nothing at all. What am I? What goes away as soon as you talk about it? It can fill a room, but it takes up no space. What is it? How many seconds are in a year? David’s parents have three sons: Snap, Crackle, and what? David’s parents have three sons: Snap, Crackle, and what? What has a neck but doesn’t have a head?