Using Boyles Law

Sample Problem C A sample of oxygen gas has a volume of 150.0 mL when its pressure is 0.947 atm. What will the volume of the gas be at a pressure of 0.987 atm if the temperature remains constant  

0 CHECK YOUR WORK When the pressure is increased slightly at constant temperature, the volume decreases slightly, as expected. Units cancel to give milliliters, a volume unit. 

A balloon filled with helium gas has a volume of 500 mL at a pressure of 1 atm. The balloon is released and reaches an altitude of 6.5 km, where the pressure is 0.5 atm. If the temperature has remained the same, what volume does the gas occupy at this height  

Balloonists, such as those in the photo at the beginning of this chapter, are making use of a physical property of gases if pressure is constant, gases expand when heated. When the temperature increases, the volume of a fixed number of gas molecules must increase if the pressure is to stay constant. At the higher temperature, the gas molecules move faster. They collide with the walls of the container more frequently and with more force. The volume of a flexible container must then increase in order for the pressure to remain the same. 

The Kelvin temperature scale is a scale that starts at a temperature corresponding to —273.15°C. That temperature is the lowest one possible. The temperature -273.15°C is referred to as absolute zero and is given a value of zero in the Kelvin scale. This fact gives the following relationship between the two temperature scales. 

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