Change in Translational KE of a gas

[Claire84]

We've been set the question of- In an isothermal expansion, and ideal gas at initial pressure Po expands until its volume is twice its initial volume. When the gas is compressed adibatically and quasi-statically ack to its original volume, its pressure is 1.32Po. How does the translational kinetic energy of the gas change in these processes? We can assume throughout that the gas is in the regime where rotational motion takes plae, but vibraional motion is frozen out.

Can someone just give me a general idea of how the translational KE of the gas changes? When it initially expands does its internal energy change at all since its temp doesn't change? If so, does this mean that there is no change in the translational energy during expansion and it only changes when it's compressed?

 

[Claire84]

Anyone have any ideas?

As iI said above (sort of!), since it's temperature doesn't change during the expansion, does this mean that there is no change in the translational KE of the gas and that it will only change during the compression?

 

[Bonfield]

You've answered your question. During the isothermal expansion, constant T means no internal energy change. During the adiabatic compression, there is no heat flow. But, work is being done on the gas and this will show up as an increased internal energy.

 

[Claire84]

Thanks very much!