13.5 – NOTES Boyle’s and Charles Law

Complete the questions in A Complete the questions in A.9 at the beginning of the notes with your partner!

Explain the following observations: Even if they have ample supplies of oxygen gas, airplane passengers experience discomfort when the cabin undergoes a drop in air pressure. When air pressure decreases, gases in the lungs, stomach and sinuses expand, creating discomfort. New tennis balls are sold in pressurized containers. Tennis ball have an internal pressure greater than atmospheric pressure to give bounce. Cans create the same pressure so gas doesn’t leak out. After descending from a high mountain, the capped, half-filled plastic water bottle from which your drank while standing at the summit now appears dented or slightly crushed. Pressure outside the bottle increases as you descend, crushing the bottle.

A.8 Pressure-Volume Behavior of Gases If you increase pressure, the volume decreases   Boyle’s Law P1V1=P2V2 Inversely proportional

Example: A sample of oxygen gas occupies a volume of 250 ml at 1 atm of pressure. If the pressure increases to 1.2 atm, what is the new volume?

A.10 Exploring Temperature-Volume Relationships Matter expands when heated   V1/T1 = V2/T2 or V1T2 = V2T1

Kelvin temperature scale SI unit of temperature   The advantage of the Kelvin scale is that it has no value for 0 degrees, and there are no negative numbers. Must be used when doing any calculation with temperature Absolute zero Lowest temperature theoretically possible 0K = -273°C K = °C +273 Molecular Motion Stops here

STP – standard temperature and pressure   1 atm and 0°C You will need to convert the temperature from Celsius to Kelvin if these conditions are used in the a problem. 273K = standard temperature in equations 1 atm = 101.3 kPa = 760 mmHg

A.11 Temperature-Volume Behavior of Gases As temperature increases, the volume will increase when the pressure is constant Linear relationship/directly proportional   Charles’ law V1/T1 = V2/T2 or V1T2 = V2T1 Volume and Temperature change when pressure is constant THE TEMPERATURE MUST BE IN KELVINS

Example: If helium occupies a volume of 3 Example: If helium occupies a volume of 3.8 L at 228 K, what volume will it occupy at 318K?  

Example: A sample of chlorine occupies a volume of 2 L at 25 C Example: A sample of chlorine occupies a volume of 2 L at 25 C. What will the temperature be if the volume expands to 4 L?