Physics - Thermal Conduction?

Question

This is a question where I'm having a little trouble understanding. Please explain this concept and how to do this problem. Thanks!

Air in a thundercloud expands as it rises. If its initial temperature is 299 K and no energy is lost by thermal conduction on expansion, what is its temperature when the initial volume has doubled?

Answer 1

If you have a given amount of gas with a given temerature, the temperature of the gas will change in proportion with its volume. Double the volume, halve the tempurature. The answer is... 149.5k!