Q:

Question about Charles' law:

Charles's law says that the volume of a given mass of a gas is directly proportional to its absolute temperature. This means if we increase one, the other one is automatically increased.
So the question that my mind is not accepting is: if we increase volume, than temperature will also increased, but in my observations, volume increased the temperature decreased? How is that possible?

A:

Charle's Law, I believe, says that if you increase volume while maintaining a constant pressure, that the temperature will increase.   Key to that relation is that a constant pressure is maintained.  
A more general law than charles law is the ideal gas equation.  $PV=nk T$  If you take $P$ to be constant in the ideal gas equation you get $V\propto T$ which is when Charles law is applicable.

