You have a balloon that is not permeable to gas molecules. The balloon is spherical and has a circumference of 3.141592654 m when it is filled with a gas at 20 EC and 1.0000 atm pressure. Explain how this could be used as a barometer and a thermometer, not necessarily using the same balloon, and then determine the circumference of the balloon when the external pressure is 1.1000 atm and 0.9980 atm and the temperature is 25 EC and 18 EC, respectively.