CHEMISTRY April 17 th, 2012

Brainteaser FRIDAY 4/20/12 Tell me how your are going to explain what happened in your experiment and WHY it happened to the rest of the class today during your presentations. Please give me the title of your experiment too.

Brainteaser MONDAY 4/23/12 According to the KMT, what happens to pressure when you:  increase the temperature?  Increase volume?  Increase the amount of gas molecules?  Decrease volume?

Objectives Pressure and Volume: Boyle’s Law  Understand the law that relates the pressure and volume of a gas  To do calculations involving this law Volume and Temperature: Charles’ Law  To learn about absolute zero.  To learn about the law relating the volume and temperature of a sample of gas at constant temperature  To do calculations involving this law. The Combined Gas Law The Ideal Gas Law  To understand the ideal gas law and use it in calculations.

Boyle’s Law: Pressure and Volume Boyle’s law states that the pressure and volume of a gas at constant temperature are inversely proportional. Inverse relationship  As pressure increases, volume decreases  As pressure decreases, volume increases This is Boyle’s Law  PV = k

Boyle’s Law We can use Boyle’s Law to compare:  Volume, at two pressures  Pressure, at two volumes In mathematical terms, this law is expressed as follows: Temperature and mass (# of particles) are constant

Boyle’s Law: Pressure and Volume A sample of compressed methane has a volume of 648 mL at a pressure of 503 kPa.  To what pressure would the methane have to be compressed in order to have a volume of 216 mL?

Charles’ Law: Temperature & Volume Charles’s Law states that, for a given amount of gas at constant pressure, the volume is directly proportional to the temperature (in kelvins). Direct Relationship  Temperature increases, volume increases  Temperature decreases, volume decreases This is Charles’ Law  V = k T

Charles’ Law: At -273 deg C or (O K), the volume of gas extrapolates to zero.  This temperature is called the absolute zero. Absolute zero is the lowest possible theoretical temperature.  Theoretically, at absolute zero, the kinetic energy of particles is zero, so all motion of gas particles at that point ceases.

Charles’ Law: Temperature and Volume We can use Charles’ Law to compare:  Temperature, at two volumes  Volume, at two temperatures In mathematical terms, this law is expressed as follows: Pressure and mass (# of particles) must be constant

Charles’ Law A weather balloon contains 5.30 kL of helium gas when the temperature is 12°C.  At what temperature will the balloon’s volume have increased to 6.00 kL?

Brainteaser WED/THURS A gas at 330 K occupies a volume of L. What volume will be occupied if the temperature drops to 273 K?

Combined Gas Law: Temperature, Volume, and Pressure Boyle’s Law and Charles’ Law can be combined to look at all 3 variables. This is the Combined Gas Law: Temperature must be in Kelvin (K)  K = C Use the combined gas law when pressure, volume or temperature are changing.

Combined Gas Law A sample of nitrogen monoxide has a volume of 72.6 mL at a temperature of 16°C and a pressure of kPa.  What volume will the sample occupy at 24°C and 99.3 kPa?