Short clever riddles for teens

I live in a hotel, on the land or in the sea, whatever could I be?

What goes on increasing every second but never decreases?

I am the place where the earth meets the sky and the water kisses the land. I disappear twice a day, only to return again. What am I?

I am sweet and tasty, sometimes hard or chewy. I wear a bright paper coat that is noisy and crinkly. Who am I?

What is the ancient invention that allows people to see through walls?

It always becomes white when it becomes dirty. What is that?

What has five fingers but is not alive?

If you had a pizza with crust thickness 'a' and radius 'z', what's the volume of the pizza?

I know a country. If you remove the last aplhabet of its name, it will become a part of your body. Do you?

I always work under pressure and by myself is the only way I'm hurt. I was formed under pressure and for woman I'm pleasure. What am I?