Presentation on theme: "Investigating The Variables of a Gas"— Presentation transcript:
1 Investigating The Variables of a Gas The Chemistry of the Gas Laws
2 The Variables of a GasGases can be described using four different variables:TemperaturePressureVolumeAmount of GasExplore each of these variable individually by clicking on the buttons belowAmount of GasTemperaturePressureVolume
3 TemperatureTemperature is a measure of a gas particle’s kinetic energy (energy of motion)Represented by the letter TTemperature can be measured in degrees Celsius (ºC) or Kelvins (K)In chemistry we will measure temperature in KelvinsTo convert a Celsius temperature into Kelvins add 273Ex. 10 ºC = 283 K
4 PressureGas pressure is caused by the force of gas particles running into the walls of their containerRepresented by the letter PThere are three units of pressure :Kilopascals (kPa), Atmospheres (atm), Millimeters of Mercury (mmHg)We will use kPa as our standard unitStandard pressure is kPa or 1 atm
5 VolumeThe volume of a gas describes the three dimensional space occupied by the particles of a gasRepresented by the letter VThe volume of a gas is measured in liters (L)Assume that if the volume of a gas changes, the walls of the container are movable. A fixed volume assumes that the container is thick and rigid.
6 Amount of GasThe number of particles in a sample of gas affects the pressure and volume of a gasRepresented by the letter nThe amount of gas is measured in moles (mol)
7 Relationship to pressure Remember that gas pressure is caused by the force of gas particles running into the walls of their container and one anotherAs the volume of the container is increased, the pressure in the container decreases because there are less collisionsAs the temperature of the gas increases, the pressure increases because particles are moving more quickly. This increases the number of collisionsAs the number of particles in a gas increase, collisions also increase. The causes an increase in pressure
8 The Gas LawsThe Gas Laws are mathematical equations that were developed in the early 18th century to explain the relationships between the variables of a gas.Click on the buttons below to explore each law.Boyle’sLawCharles’LawGay-Lussac’sLaw
9 Boyle’s LawBoyle’s Law relates the variables of pressure and volumeAccording to this law, as the volume of a container decreases, the pressure of the gas increasesThis is an inverse relationshipThe equation for Boyle’s Law is written as:P1V1 = P2V2
10 Real World ExampleA real world example of Boyle’s Law involves squeezing a balloonAs the balloon is squeezed the volume of the container decreasesThis increased the gas pressure inside the balloonIf the pressure becomes too great the balloon pops
11 Boyle’s Law DemoWatch the following YouTube video to see Boyle’s Law in action
12 Boyle’s Law Calculation If we have 4 L of methane gas at a pressure of kPa, what will be the pressure of the gas if we squish it down so it has a volume of 2.5 L?P1 = kPaV1 = 4 LP2 = ???V2 = 2.5 LP1V1 = P2V2101.3 x 4 = P2 x 2.5405.2 = P2 x 2.5÷ ÷2.5kPa = P2Return to Gas Laws
13 Charles’ LawCharles’ Law relates the variables of volume and temperatureAccording to this law, as the temperature of a gas decreases, the volume of the gas also decreasesThis is a direct relationshipThe equation for Charles’ Law is written as:V1/T1 = V2/T2
14 Real World ExampleA real world example of Charles’ Law is lower tire pressure in the winterDuring the winter months, the average outdoor temperature decreasesThis decrease in temperature causes gas particles to move closer togetherThis decreases the volume of the gas inside the tire
15 Charles’ Law DemoWatch the following YouTube video to see Charles’ Law in action
16 Charles’ Law Calculation If we have 2 L of methane gas at a temperature of 313 Kelvin, what will the volume be if we heat the gas to 353 K?V1 = 2LT1 = 313 KV2 = ???T2 = 353 KV1/T1 = V2/T22 ÷ 313 = V2 ÷ 3530.006 = V2 ÷ 353x x 3532.25 L= V2Return to Gas Laws
17 Gay-Lussac’s Law P1/T1 = P2/T2 Gay-Lussac’s Law relates the variables of pressure and temperatureAccording to this law, as the temperature of a gas decreases, the pressure of the gas also decreasesThis is a direct relationshipThe equation for Gay Lussac’s Law is written as:P1/T1 = P2/T2
18 Real World ExampleA real world example of Gay-Lussac’s Law is throwing an aerosol can in a fireWhen the can hits the fire the temperature of the gas increasesThis increase in temperature causes an increase in pressureSince the volume of the can is constant, it will eventually explode
19 Gay Lussac’s Law DemoWatch the following YouTube video to see Gay Lussac’s Law in action
20 Gay Lussac’s’ Law Calculation A gas has a pressure of 93.2 kPa at 313 K. What is the temperature at kPa?P1 = kPaT1 = 313 KP2 = kPaT2 = ???P1/T1 = P2/T293.2 / 313 = / T2Cross Multiply93.2 x T2 = x 31393.2 x T2 =÷ ÷93.2T2 = KReturn to Gas LawsQuiz
21 QuizAre you ready to take the quiz??? If not, go back and review the gas laws first.
22 Question 1 A. Boyle’s Law B. Charles’s Law C. Gay-Lussac’s Law Which Gas Law is illustrated in the problem below?A weather balloon was initially at a pressure of kPa, and its volume was 35.0 L. The pressure is decreased to 76 kPa without loss of gas or change in temperature. What is the new volume?A. Boyle’s LawB. Charles’s LawC. Gay-Lussac’s LawD. None of the Above
23 Go Back and Review the Gas Laws Try Again!Go Back and Review the Gas Laws
25 Question 2 A. 27.6 L B. 27.6 kPa C. 44.3 L D. 44.3 kPa A weather balloon was initially at a pressure of kPa, and its volume was 35.0 L. The pressure is decreased to 76 kPa without loss of gas or change in temperature. What is the new volume?A LB kPaC LD kPa
26 Go Back and Review the Gas Laws Try Again!Go Back and Review the Gas Laws
28 Question 3A man heats a balloon in the oven. If the balloon initially has a volume of 0.4 liters and a temperature of 293 K, what will the volume of the balloon be after he heats it to a temperature of 523 K?A LB LC LD L
29 Go Back and Review the Gas Laws Try Again!Go Back and Review the Gas Laws
34 PTV SticksWatch the following YouTube video. After viewing the video you should create your own PTV stick using a piece of paper and a marker
35 Using your PTV SticksNow that you’ve created your own PTV stick, go through the following scenarios to see why these relationships are important in the real world. Try to come up with your own explanation using the PTV stick before clicking ahead to the answers
36 When a ping pong ball gets dented, the dent can be removed by placing the ball in hot water. If volume is held constant, why does this work?
37 If volume of the container is held relatively constant, as the temperature of the gas inside the ball increase, the pressure also increases. This pushes out the dent (Gay- Lussac’s Law)
38 As air bubbles rise to the surface of the ocean, their volume increases. Assuming the water temperature is relatively constant as the bubbles rise, why does this occur?
39 As the bubbles rise there is less water above them As the bubbles rise there is less water above them. This reduces the pressure on the bubbles allowing them to expand. Therefore the volume increases. (Boyle’s Law)
40 Why does a hot air balloon rise when the air inside the balloon is heated. Assume the surrounding air pressure is relatively constant as the balloon rises.
41 As the air is heated, the air molecules expand As the air is heated, the air molecules expand. As they expand, the air volume increases and becomes less dense than the cooler surrounding air. This allows the balloon to rise. (Charles’ Law)
42 Assuming the volume of the tire is held relatively constant, why would it be best to take your tire pressure before you drive?
43 As you drive the temperature of the air in your tires increases As you drive the temperature of the air in your tires increases. As the temperature increases the gas molecules spread out and create a higher tire pressure. (Gay-Lussac’s Law)
44 Why does blood enter a syringe when the plunger of the syringe is pulled out? Assume the temperature in the syringe remains constant
45 As the plunger is pulled out the volume of the container increases As the plunger is pulled out the volume of the container increases. As the volume increases, the pressure inside the syringe decreases, therefore creating a suction effect and drawing the blood in. (Boyle’s Law)
46 Now it’s your turn! Come up with at least two real world scenarios that relate to the gas laws. Once you have come up with your examples get them checked by Mrs. Turner and then add them to the class wiki