Presentation on theme: "Investigating The Variables of a Gas"— Presentation transcript:
1Investigating The Variables of a Gas The Chemistry of the Gas Laws
2The 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
3TemperatureTemperature 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
4PressureGas 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
5VolumeThe 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.
6Amount 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)
7Relationship 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
8The 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
9Boyle’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
10Real 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
11Boyle’s Law DemoWatch the following YouTube video to see Boyle’s Law in action
12Boyle’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
13Charles’ 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
14Real 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
15Charles’ Law DemoWatch the following YouTube video to see Charles’ Law in action
16Charles’ 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
17Gay-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
18Real 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
19Gay Lussac’s Law DemoWatch the following YouTube video to see Gay Lussac’s Law in action
20Gay 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
21QuizAre you ready to take the quiz??? If not, go back and review the gas laws first.
22Question 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
23Go Back and Review the Gas Laws Try Again!Go Back and Review the Gas Laws
25Question 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
26Go Back and Review the Gas Laws Try Again!Go Back and Review the Gas Laws
28Question 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
29Go Back and Review the Gas Laws Try Again!Go Back and Review the Gas Laws
34PTV SticksWatch the following YouTube video. After viewing the video you should create your own PTV stick using a piece of paper and a marker
35Using 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
36When 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?
37If 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)
38As 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?
39As 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)
40Why 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.
41As 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)
42Assuming the volume of the tire is held relatively constant, why would it be best to take your tire pressure before you drive?
43As 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)
44Why does blood enter a syringe when the plunger of the syringe is pulled out? Assume the temperature in the syringe remains constant
45As 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)
46Now 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