When air of the atmosphere rises up, it cools. Why?

The air of the atmosphere becomes cool at higher altitudes due to

A: Hot air balloon rises up by displacing the denser air of the atmosphere. R: The given mass of a gas becomes less denser.

A: Hot air balloon rises up by displacing the denser air of the atmosphere. R: The given mass of a gas becomes less denser.

ļn an open room at atmospheric pressure, the total kinetic energy of all the air molecules is more when the room is warm than the total kinetic energy of the molecules in the same room when it is cool. Justify this statement.

When the air cools, its density :

If an inflated tyre bursts, the air escaping out is cooled. Why?

Air gets thinner as we go up in the atmosphere. Will the velocity of sound change?