Physical Science / Unit 2: Properties and States of Matter
2.5 Gas Behavior
Notes
Gas particles hit the walls of a container, creating pressure.
- Boyle's law: at constant temperature, pressure and volume are inversely related: $P_1V_1 = P_2V_2$.
- Charles's law: at constant pressure, volume is directly proportional to temperature measured in kelvin: $\displaystyle \frac{V_1}{T_1} = \frac{V_2}{T_2}$.
- Kelvin = Celsius + 273.
- Example (Boyle): 6 L of gas at 2 atm is compressed to 4 atm. $2 \times 6 = 4 \times V_2$, so $V_2 = 3$ L.
- Heating a gas in a sealed rigid container raises its pressure.
Practice
A gas at 1 atm has a volume of 8 L. If the pressure is raised to 4 atm at constant temperature, the new volume is:
$1 \times 8 = 4 \times V_2$, so $V_2 = 2$ L.
A balloon has a volume of 2 L at 300 K. At constant pressure it is heated to 600 K. Its new volume is:
Doubling the kelvin temperature doubles the volume: $\displaystyle \frac{2}{300} = \frac{V_2}{600}$.
Why does the pressure in a sealed car tire increase on a hot day?
Higher temperature means faster particles and more forceful collisions.
Ready for more? Take the Unit 2 test.