Question

explain why the tempr of gas drops in adiabatic process?

Answer 1

Answer:

It doesn't always drop.

Explanation:

The definition of an adiabatic process is that there is no change in heat of the system.

So by energy conservation (or First Law of thermodynamics in lingo of thermodynamics),

$\Delta Q = \Delta U + W_{done}\\\to \Delta U = -W \ (since \ \Delta Q = 0)$

So the temperature (which is directly proportional to $\Delta U = \frac{fnR\Delta T}{2}$) will be proportional to the negative of the work done.

So the temperature will drop in case of adiabatic 'expansion' and will rise in case of adiabatic 'compression'.

Another way to look at it is to consider that there is no energy entering or exiting the system. So if there is expansion, that energy for the process has to come from somewhere. This energy thereby comes from the temperature drop.

You can think of a similar situation in case of compression(energy released by compression goes into temperature change)