2Particles of Ideal vs Real Gas have no volumehave their own volumedon’t attract or repel each otherattract each otherhave elastic collisionshave collisions that are not elastic
3How gases behave Gas behavior is most ideal… at low pressures at high temperaturesin nonpolar atoms/molecules**Always use Kelvin temperatures when working with gases
4Defining Gas Pressurepressure of a gas is caused by the collisions of the particles in the gas on the walls of their container.
5The more often gas particles collide with the walls of their container, the greater the pressure
6Defining Gas Pressuremore air particles inside the ball mean more mass inside.
7pressure of a gas is directly proportional to its mass. P α M How are number of particles and gas pressure related?pressure of a gas is directly proportional to its mass.P α MIf m then p
8How are temperature and pressure related? At higher temperatures, the particles in a gas have greater kinetic energy.move faster and collide with the walls of the container more often and with greater force, so the pressure rises.
9If the volume of the container stays constant & How are temperature and pressure related?If the volume of the container stays constant &# of particles of gas stays constantThen pressure increases in direct proportion to the Kelvin temperature.
10pressure of a gas is directly proportional to its Kelvin temperature. How are temperature and pressure related?pressure of a gas is directly proportional to its Kelvin temperature.P α TIf t then p
11Devices to Measure Pressure barometer - instrument that measures the pressure exerted by the atmosphere.The height of the mercury column measures the pressure exerted by the atmosphere
12The BarometerThe standard atmosphere (atm) is defined as the pressure that supports a 760-mm column of mercury.****remember atmospheric pressure decreases with altitude because the depth of air above you is less
13Pressure UnitsAtmospheric pressure is the force per unit area that the gases in the atmosphere exert on the surface of Earth.The SI unit for measuring pressure is the pascal (Pa),
14Pressure UnitsBecause the pascal is a small pressure unit, it is more convenient to use the kilopascal. 1 kilopascal (kPa) is equivalent to 1000 pascals.1 atm = kPa
15The Gas LawsThe gas laws apply to ideal gases, which are described by the kinetic theory
162) If pressure decreases then volume increases Boyle’s Law: Pressure and VolumeAfter performing many experiments with gases. Boyle had four findings.at constant temperatures,If pressure increasesthen volume decreases2) If pressure decreasesthen volume increases
17Boyle’s Law: Pressure and Volume Boyle’s law states that the pressure and volume of a gas at constant temperature are indirectly proportional.Click box to view movie clip.
18Boyle’s LawIn mathematical terms, this law is expressed as follows.
20Kinetic explanation of Boyle’s Law At a constant temperature, the pressure exerted by a gas depends on the frequency of collisions between gas particles and the container.If the same number of particles is squeezed into a smaller space (decreased volume), the frequency of collisions increases, thereby increasing the pressure.
22Applying Boyle’s LawA 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?Examine the Boyle’s law equation. You need to find P2, the new pressure, so solve the equation for P2.
23Applying Boyle’s LawSubstitute known values and solve.
24Charles’s Law: Temperature and Volume At constant pressureIf the temperature is increased,if the volume is free to change, thenThe volume increases
25Charles’s LawCharles’s law states that the volume and temperature of a gas at constant pressure are directly proportionalClick box to view movie clip.
26Kinetic explanation of Charles’s Law If the temperature is increased, average kinetic energy and particle movement increases and if volume is free to change it increases too
28Applying Charles’s 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?Start by converting the given temperature to kelvins.
29Applying Charles’s Law Next, solve the Charles’s law equation for the new temperature, T2.
30Applying Charles’s Law Then, substitute the known values and compute the result.Finally, convert the Kelvin temperature back to Celsius.New Temperature = 323 – 273 = 50oC
31T1 T2 GAY-LUSSAC’S LAW – pressure and temperature At constant volume If the temperature is increased,Then pressure increasesP1 = P2T1 T2
32GAY-LUSSAC’S LAWGay- Lussac’s law states that the temperature and pressure of a gas at constant volume are directly proportional
33Kinetic explanation of Gay-Lussac’s Law If the temperature is increased, average kinetic energy and particle movement increases and collisions occur more frequently, thereby increasing pressure
35“Potato Chips are Very Good To Bite.” Pressure constant – CharlesVolume constant – Gay-LussacTemperature constant – Boyle
36The Combined Gas LawThe gas laws may be combined into a single law, called the combined gas law, that relates two sets of conditions of pressure, volume, and temperature by the following equation.With this equation, you can find the value of any one of the variables if you know the other five.
37Applying the 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?Start by converting the temperatures to kelvins.
38Applying the Combined Gas Law Next, solve the combined gas law equation for the quantity to be determined, the new volume, V2.
39Applying the Combined Gas Law Substitute the known quantities and compute V2.
40STP = Standard Temperature & Pressure 0°C and1 atm
41Avogadro’s PrincipleAvogadro’s principle - equal volumes of gases at the same temperature and pressure contain the same number of particles.An extension of Avogadro’s principle is that one mole (6.02 x 1023 particles) of any gas at STP (standard temperature and pressure -0°C and 1.00 atm pressure) occupies a volume of 22.4 L.needs a multiply sign instead of an “x”
42Applying Avogadro’s Principle What is the volume of 7.17 g of neon gas at 24°C and 1.05 atm?Start by converting the mass of neon to moles.The periodic table tells you that the atomic mass of neon is amu. Therefore, the molar mass of neon is g.needs a multiply sign instead of an “x”
43Applying Avogadro’s Principle Gases: Basic ConceptsTopic13Applying Avogadro’s PrincipleNext, determine the volume at STP of mol Ne.If you needed only the volume at STP, you could stop here.Finally, use the combined gas law equation to determine the volume of the neon at 24°C and 1.05 atm pressure.needs a multiply sign instead of an “x”
44Applying Avogadro’s Principle Gases: Basic ConceptsTopic13Applying Avogadro’s Principleneeds a multiply sign instead of an “x”
45Basic Assessment Questions Topic13Question 4What pressure will be needed to reduce the volume of 77.4 L of helium at 98.0 kPa to a volume of 60.0 L?