Presentation on theme: "Kinetic Molecular Theory of Gases and the Gas Laws"— Presentation transcript:
1Kinetic Molecular Theory of Gases and the Gas Laws
2Properties of Gases Gases are fluids Gases are highly compressible Fluids are any substance that flowsGases are highly compressibleExample: Tire pressureGases completely fill containersGases have lower densities than liquids and solids
3Kinetic Molecular Theory KMT describes the motion of the particlesParticles have the same motion as billiard balls
4KMT of Gases Assumptions: Gas molecules are in constant, random motion Gas molecules are separated by large distancesGas molecules have no attractive/repulsive forcesCollisions are considered to be perfectly elastic ( no energy is lost )
5Temperature of GasesTemperature and energy of gases are directly proportionalAs the temperature increases, kinetic energy of the molecules increasesAs temperature decreases, kinetic energy will also decrease
6Pressure of GasesAt sea level, the standard gas pressure is 1 atmospherePressure is the force exerted by gas moleculesStandard Temperature and Pressure (STP) is equal to 1 atm and 0 °C.Note:1 ATM is measured from the surface of the ocean (sea level) to the top of the sky (stratosphere)
7Different Units of Pressure Atmosphere ( atm)Torr / millimeter of mercury mm HgPounds per square inch (psi)Pascal of kilo Pascal (Pa or kPa)Conversions vs. 1 ATM760 mm Hg or Torr14.7 psikPa
8Converting Pressure Example Convert 72.7 atmospheres (atm) into kilopascals (kPa)Convert 31.2 psi to ATM
9Variables in Gas Equations: The Gas LawsVariables in Gas Equations:P = Pressure (kPa or atm)V = Volume (L)T = Temperature (K)n = amount of gas (moles)
10Boyle’s LawStates that for a fixed amount of gas at constant temperature the volume of the gas is inversely proportional to the pressure of a gasPressureVolume
11Boyle’s Law Example Problem The pressure on 2.50 L of anesthetic gas changes from 105 kPa to 40.5 kPa. What will be the new volume if the temperature remains constant?
12Boyle’s Law Example Problem A high-altitude balloon contains 30.0 L of helium gas at 103 kPa. As the balloon rises, you record a new volume of L. What is the atmospheric pressure in kPa? (Assume constant temperature)
13Charles’s LawStates that the volume of a gas is directly proportional to the Kelvin temperature if the pressure remains constantTemperatureVolume
14Charles’s Law Example Problem The air in a hot air balloon has a volume of L at 30.0°C (303 K). What will the volume be if the temperature is raised to °C (393 K)?
15Charles’s Law Example Problem An aerosol can has a volume of 3.00 x 102 mL at °C is heated until its volume is 6.00 x 102 mL. What is the new temperature (in K) of the gas if pressure remains constant?
16Gay-Lussac’s LawStates that the pressure of a gas is directly proportional to the Kelvin temperature if the volume remains constantTemperaturePressure
17Gay-Lussac’s Law Example Problem The gas left in a used aerosol can is at a pressure of 103 kPa at 25 °C. If this can is thrown onto a fire, what is the pressure of the gas when its temperature reaches 928 °C?
18Gay-Lussac’s Law Example Problem A sealed cylinder of gas contains nitrogen gas at x 103 kPa pressure and a temperature of °C. The cylinder is left in the sun, and the temperature of the gas increases to 50.0 °C. What is the new pressure in the cylinder?
19Combined Gas LawA single equation that combines all the gas laws:
20Combined Gas Law Example Problem A gas takes up a volume of 17 liters, has a pressure of 2.3 atm, and a temperature of 299 K. If I raise the temperature to 350 K and lower the pressure to 1.5 atm, what is the new volume of the gas?
21Ideal Gas Law Relates the gas laws and the amount of gas Requires the gas constant, RR can be a different number depending on the units
22PV = nRT Example Problem A container of 3.0 L of nitrogen (N2) is at a pressure of 4.5 x 102 kPa and a temperature of 39 °C. How many grams of N2 are in the container?
23Ideal Gas Law Example Problem What pressure will be exerted by mol of a gas at 25.0 °C if it is contained in a L vessel?
24Avogadro’s Hypothesis Equal volumes of gases at the same temperature and pressure contain equal numbers of particlesDue mainly to the large amount of empty space between particlesFrom this, scientists have determined that 1 mol = 22.4 L at STP
25This was not well accepted Why?Tennis balls vs. Bowling balls