Simple riddles for teens

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?

I eat insects. I live in the pond. I hop. I am green. What am I?

When you don't have me, you want me, but when you do have me, you want to give me away. What am I?

If you see a bird sitting on a twig, how could you get the twig without disturbing the bird?

What goes in dry and hard, but comes out wet and soft?

I have no legs. I will never walk, but always run. What am I?

Four children and their pet dog were walking under a small umbrella. But none of them became wet. How?

I can run, but not walk. Thought is not far behind me. What am I?

Physicists have built devices to move me very fast. My last seven letters can be commonly found in newspapers, magazines and journals. What am I?

Which vehicle is spelled the same forwards and backwards?