[SOLVED] Gas laws 1. The problem statement, all variables and given/known data A balloon containing 2000m^3 of helium gas at 1.00atm and a temperature of 15.0 C rises from ground level to an altitude at which the atmospheric pressure is only 0.900atm. Assume the helium behaves like an ideal gas and the balloon's ascent is too rapid to permit much heat exchange with the surrounding air. Calculate both the volume and the temperature of the gas at the higher altitude. 2. Relevant equations Ideal gas equation; combined gas law. 3. The attempt at a solution Not really sure how to procede... If I had the new temperature, i could find the new volume, and vice versa, but without either, I'm stuck. Also, if there is little heat exchange with the surrounding air, how does the temperature change?