The phenomenon of sound propagation in air is

For an adiabatic process,the wrong statement is:

Can a change in the internal energy of an ideal gas be considered an adiabatic process?

The relation between volume $(V)$ and absolute temperature $(T)$ of a gas in an adiabatic process is

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

For an adiabatic process with $\gamma = 2.5$,if the volume of a gas is reduced to $1/8$ of its initial volume,what will be the new pressure $P'$ in terms of the initial pressure $P$?