New Area of Focus: Gases and Other Laws. New Area of Focus: Gases and Other Laws. Copyright 2010 Ryan P. Murphy Gay-Lussac's Law: The pressure exerted on the sides of a container by an ideal gas of fixed volume is proportional to its temperature. Sometimes referred to as Amontons' Law Pressure - raises the temperature at which a given type of matter changes states, such as going from solid to liquid or liquid to gas. For example, water boils at 212 degrees Fahrenheit at sea level. At higher altitudes, the pressure from the atmosphere decreases and therefore lowers the boiling point. Charles Law: Volume of a gas increases with temperature. (Gases expand with heat and particles move closer when cooled). Charles Law: Volume of a gas increases with temperature. (Gases expand with heat and particles move closer when cooled). Copyright 2010 Ryan P. Murphy The formula for the law is The formula for the law is V1 = V2 T1T2 V1/ T1- volume and temperature before change occurs V2/T2- volume and temperature after change occurs Copyright 2010 Ryan P. Murphy You have a gas filled balloon with a volume of 20 and a temp of 4 K and you cool it down to half the temp, the volume will decrease by half. (particles move closer together) Ex. 20 = 10 4 (remove heat)2 Copyright 2010 Ryan P. Murphy Charles Law A sample of nitrogen occupies a volume of 250 mL at 25 degrees C. What volume will it occupy at 95 degrees C? Absolute zero- this concept was developed by Charles. Represents the temp at which all molecules stop moving. Study a few minutes. Questions will follow. Gases are made up of molecules which are in constant random motion.. Pressure is due to collisions between the molecules and the walls of the container. All collisions, both between the molecules themselves, and between the molecules and the walls of the container, are perfectly elastic. (That means that there is no loss of kinetic energy during the collision.) The temperature of the gas is proportional to the average kinetic energy of the molecules. There are no intermolecular forces between the gas molecules. The volume occupied by the molecules themselves is entirely negligible relative to the volume of the container. The kinetic movement of molecules causes gas particles to move to open areas. Copyright 2010 Ryan P. Murphy When pressure is increased on a gas its volume is decreased. Which container has the higher density? Since density is defined to be the mass divided by the volume, density depends directly on the size of the container in which a fixed mass of gas is confined. Which container has the higher density? Since density is defined to be the mass divided by the volume, density depends directly on the size of the container in which a fixed mass of gas is confined. Demonstration! Marshmallow Torture Place Marshmallow into Bell Jar vacuum. Remove Air from Bell Jar Record Picture of Marshmallow. Quickly let air rush back in and observe. Boyles Law Formula P1V1= P2V2 P1V1- pressure and volume before change occurs P2V2- pressure and volume after change occurs If you have a 2 liter filled with gas at a pressure of 50 and you shrink it down to a 1 liter container, the pressure will increase to 100 Ex. 50(2)= 100(1) (reduce volume) 100=100 Example Boyles Law: Pressure and Volume are inversely proportional. Boyles Law: Pressure and Volume are inversely proportional. Copyright 2010 Ryan P. Murphy Boyles Law A sample of oxygen gas occupies a volume of 250 mL at 740 torr pressure. What volume will it occupy at 800 torr pressure? Combined Gas Law Describes the relationship among the temperature, volume and pressure of a gas when the number of particles is constant. Describes the relationship among the temperature, volume and pressure of a gas when the number of particles is constant. (P 1 V 1 )/T 1 = (P 2 V 2 )/T 2 (P 1 V 1 )/T 1 = (P 2 V 2 )/T 2 P 1 V 1 = P 2 V 2 P 1 V 1 = P 2 V 2 T 1 T 2 T 1 T 2 Combined Gas Law: P1= 1.5 atm V1= 3.0L T1= 20 C P2= 2.5 atm V2= ? T2= 30 C Temperature and Pressure Temperature and Pressure As temp rises, pressure rises Watch out As temp rises, pressure rises Watch out As pressure rises, temp rises Watch out As pressure rises, temp rises Watch out Copyright 2010 Ryan P. Murphy Avogadros Law / Hypothesis. Copyright 2010 Ryan P. Murphy Avogadro's Law: Equal volumes of gases, at the same temperature and pressure, contain the same number of particles, or molecules. Copyright 2010 Ryan P. Murphy The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) Copyright 2010 Ryan P. Murphy The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) Copyright 2010 Ryan P. Murphy The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) Copyright 2010 Ryan P. Murphy The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) Copyright 2010 Ryan P. Murphy The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) Copyright 2010 Ryan P. Murphy The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) Copyright 2010 Ryan P. Murphy The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) The ideal gas law: PV = nRT (pressure times volume equals the number of molecules times the gas constant times temperature) Copyright 2010 Ryan P. Murphy P=V=n=R=T= P=PressureV=Volume is equal to the.. n= Number of molecules R= Gas constant = JK m T= Temperature Copyright 2010 Ryan P. Murphy P=PressureV=Volume is equal to the.. n= Number of molecules R= Gas constant = JK m T= Temperature Copyright 2010 Ryan P. Murphy Mole is a unit of measurement used in chemistry to express amounts of a chemical substance. 8.134 JK m Ideal Gas Law (PV= nRT) How many moles of oxygen will occupy a volume of 2.5 liters at 1.2 atm and 25 C? Video Link! (Optional) Khan Academy Ideal Gas Law (Advanced) http://www.khanacademy.org/video/ideal-gas- equation--pv-nrt?playlist=Chemistryhttp://www.khanacademy.org/video/ideal-gas- equation--pv-nrt?playlist=Chemistry