The Ideal Gas Laws

The Ideal Gas LawsThe overall guiding idea for this presentation is to assess their own ideas on how the world works (assuming they have them) and then have them constantly reassess as new information is presented. The first question is to ask them what their general knowledge is of the variables concerning each of the gas laws, then present new information to them about real life examples of the gas laws that they can then use to assess whether or not their previous hypotheses were correct.

Today were going to discuss the Ideal Gas Laws and use it as an opportunity to try and discover the overall Ideal Gas Law equation for ourselves. To start, we need to examine the three main components of the Gas Laws. Ordered by ascending years of publication, we will look at Boyles Law, Charless Law, and Avogadros Law. Advance to the next slide now.1Discovering Boyles LawBoyles Law: Describes the relation between Pressure and Volume when temperature and mass are kept constant.

When the pressure acting on a system increases, will the volume of the system increase or decrease? Justify your reasoning.Have the students make a hypothesis, rationalizing a reason behind it and forcing them to think on why they believe their prediction.

Boyles Law is named after Robert Boyle, an Irish chemist who lived in the mid to late 1600s. This law describes the relationship between pressure and volume. Take a moment to think on what you know about pressure and volume and answer the question on the screen. Remember, were not worried about being right or wrong. You very well may have little to no knowledge on these two ideas. Science is all about being wrong and then discovering the right answers through observation and testing. Whats important is to be open to changing your opinions as we go forward. Pause the lecture now and take as much time as you need and spend time justifying why you believe in your hypothesis. When you are ready, click on to the next slide. [Pause]2Examples of Boyles LawBalloon Experiment When you go up a steep hill, some times you can feel a distinct popping sensation in your ears as air escapes past your ears.

Bubbles increase in size as they approach the surface of waterHere, I quickly mention some real life examples of Boyles law. The linked video I would make myself without the explanations and I would try to have them explain what they are observing. I would have them pause to watch the video and then continue to hear explanations of the real life phenomena. At the end, I would ask them to review the previous hypothesis they made and explain any changes they would make and why they changed their mind.

Now that we have a working hypothesis, examine the following pieces of evidence. Pause the lecture and spend a few minutes watching the above balloon experiment video. [Pause] Now that youve watched the video, its time to understand what it is showing us. As they press on the syringe, the balloon size shrinks. Does it appear volume and pressure are directly related, meaning that as pressure increases volume does as well? Or does it appear that they are inversely related, and that as one of them goes up, the other goes down? Think about when you go up a steep hill. You may notice a popping sensation that occurs. We know that pressure decreases as you go higher and higher above sea level, so why would the air escape from your ear? Lastly, an interesting phenomena occurs with air bubbles that rise from the deep sea. As they get closer to the surface, they can be seen to grow in size. Using the same logic from the previous example that pressure decreases as you go higher and higher towards sea level, does this example suggest they are directly or inversely related? At this time, take a moment to reassess your previous hypothesis. Does it seem to agree with the data presented here? Or are revisions needed? Feel free to revise your answer entirely or add on additional information at this time. Pause the lecture and take as long as you need before continuing to the next slide. [Pause]3Boyles LawPressure and Volume are inversely relatedIf one goes up, the other must go down.

Here, I explain Boyles law and give a small gif image for them to play to see a direct example of it, which I explain and tell them to pause the video to watch the image as many times as necessary for them before continuing onward.

Here, there is a clip showing you Boyles law in a scientific light. Feel free to pause the lecture now and watch the clip as many times as needed. [Pause] In this clip, pressure is added to the system in the form of the green weights on top of the red piston. The volume is the physical amount of space that the yellow substance occupies. As you can see, as the pressure on the system is increased, the volume drops. Likewise, as the volume is allowed to increase again, the pressure is dropped. As one variable goes up, the other goes down. This means that the gas laws are inversely related. Does this agree with the hypothesis you stipulated? Take a moment to pause this lecture and click to the next slide once you feel that youve reviewed your hypothesis enough. [Pause]4Applying Boyles LawSome deep sea fish have a special organ known as a gas bladder, a special pouch filled with air that helps to control their buoyancy. When these fish are brought to the surface, they die as a direct consequence of Boyles Law affecting this organ. Why is this?Here, now that Boyles law has been explained, I would ask them to try and pause the video for a moment to answer the above question to demonstrate understanding of the problem.

Now, to apply the knowledge you just obtained of Boyles law. Take as much time as needed to review the following question. Be sure to answer the question on your worksheet as thoroughly as possible, trying to incorporate Boyles law. Remember, you are allowed to be wrong here. Whats important is to try to apply the information you just learned as coherently as possible. Pause the lecture now and click onto the next slide when you are ready. [Pause]5Discovering Charless LawCharless Law: Describes the relation between pressure and temperature if volume and mass are kept constant.When the temperature of a system increases, will the pressure of it increase or decrease? Justify your reasoning.

Rinse, Wash, Repeat

Next, we take a look at Charless Law. Charless Law was named after Jacques Charles, a French physicist and hot air balloon researcher/enthusiast that lived in the late 1700s and early 1800s. This law is used to describe the relation between the pressure and temperature of a system. As with before, take a moment to think on what you know about temperature and pressure to develop your own hypothesis on if these two variables are directly or inversely related, being sure to justify them as much as possible. Pause the lecture now and click onto the next slide when you are ready to continue. [Pause]6Examples of Charless LawEggs and MicrowavesIf you leave a soda can in the sun, it will eventually burst from the internal pressureWhen you put a balloon in the fridge, the volume drops

Now that you have a working hypothesis, lets examine three pieces of data for Charless Law. First, watch the video above that shows what happens when you put an ostrich egg in the microwave. Pause the lecture now and continue when you have watched the video. [Pause] As you can see, there was a pretty destructive result. As the egg heated up in the microwave, pressure in the egg built up until the egg shell could no longer contain it, resulting in the following explosion. Similar to this, if you have ever left a soda can long enough in direct sunlight, you may have noticed the can starts to puff up and swell, eventually bursting open if left in sunlight long enough as a result of pressure increase. On the opposite side of the scale, if you attempt to throw a full balloon in your fridge, you will notice it decreases in size, as the pressure inside the balloon is dropping. Now that youve examined these pieces of data, take a moment to look at your hypothesis and revise it as you feel is necessary. Pause the lecture now and click onto the next slide when you are ready to continue. [Pause]7Charless LawTemperature and Gas are directly related.If one goes up, the other must as well.

Here is a video that shows the relationship between temperature and pressure. Take a moment to pause the lecture and watch the clip as many times as needed. [Pause] In this clip, the small little Bunsen burner and flame is meant to show increasing temperature, while the yellow stuff again represents volume. As you can see, as temperature increases, volume increases as well. Now, you may be thinking Wait a minute, werent we discussing pressure and temperature? Remember, all of these variables are intrinsically related. If you were going to stop the volume from increasing, what would you do? Pause the lecture for a moment and think about what you would do and write down a response. [Pause] The only way for the volume to be kept constant would be to use the red piston to increase the pressure and physically hold back this attempted change. Thus, if temperature increases, pressure must increase as well to maintain a constant volume, which can be simplified as temperature and pressure are directly related variables. Does this agree or disagree with your hypothesis? Take a moment to revise your hypothesis however necessary. Pause the lecture now and click to the next slide when you are ready. [Pause]8Applying Charless LawIf you apply spray paint for an extended period of time, the can will be cool to the touch. Why?Now that we have covered Charless law, lets look at an application of it. If you use spray paint or any other pressurized air product such as hair spray, keyboard cleaners, and so on, you may notice that the can appears to get colder after using it for an extended period of time. Take a moment to think on your new found information of Charless Law and write down an answer for why this could be. Again, dont be afraid to be wrong. Being wrong is one of the quickest ways to learn, as long as youre willing to reevaluate your knowledge of how the world works. Pause the video now and click on to the next slide when you are ready to continue. [Pause]9Discovering Avogadros LawAvogadros Law: Describes the relationship between Volume and Moles (the number of atoms present) when pressure and temperature remain constant.If you added more moles (stuff) to a system, would the volume of it increase or decrease? Justify your reasoning.Rinse, Wash, Repeat

The name Avogadro should sound familiar to most of you. Amedeo Avogadro was an Italian chemist who lived in the 1800s, perhaps best known for Avogadros number which tells you how many physical molecules or atoms are present in a single mole of substance. In addition to this, he is also known for Avogadros Law, which describes the relationship between Volume and Mass, most typically represented in moles. Take a moment to answer, if you would increase the number of moles in a system, would the volume increase or decrease? Pause the video now and click on to the next slide when you are ready. [Pause]10Examples of Avogadros LawLungs expand as they fill with air.An untied balloon deflates when you let it go.A tire deflates if punctured

Here are three basic examples of Avogadros law. Every time you breath, you are showing Avogadros law in action. If you expand your lungs, which increases their volume, they become filled with air. Similarly, if you let an untied balloon go, you would watch it fly through the air as it let all of its mass out. A final example, which many poor souls experience every day, is that when a nail or something similar punctures a car tire, the air escapes as the tire deflates. Take a moment now to review your initial hypothesis on Avogadros law. Pause the video now and make any corrections you deem relevant, clicking onto the next slide when you are ready.11Avogadros LawVolume and mole amounts are directly relatedIf one goes up, the other must go up.

NOTE: I havent found a graphic I like for this yet as I did for the other two, but I intend to replace this image for it when I find it.

Take a moment to watch the clip here, pausing the lecture for as long as needed. [Pause] As you can see here, the grey piston has no change in the pressure and merely sits on top of the container. As we add mass, the volume increases. Likewise, when we let mass escape, we witness the volume decreasing. Avogadros law states that, as the mole amount of a substance increases in a system, the volume of the system must increase to accommodate it. We can state as such that volume and moles are directly related. Does this agree with your hypothesis? Pause the lecture now and click onto the next slide once youve revised as necessary. 12Applying Avogadros LawDespite having equal volumes at the same temperature and pressure, a balloon filled with helium weighs less than a balloon filled with oxygen. Why is that?Lastly, to apply Avogadros law. This one is a bit more tricky than the last, so take your time when thinking about this. When having equal volumes, pressures, moles and temperatures, a balloon filled with helium weighs less than a balloon filled with oxygen. Why is that? Pause the video now and take your time when answering this question before clicking onto the next slide. [Pause]13Putting it all togetherReview:Boyles Law: Pressure and volume are inversely relatedCharless Law:Pressure and temperature are directly relatedAvogadros Law: Volume and pressure are directly relatedNow, lets briefly review. Boyles Law states that pressure and volume are inversely related. If one goes up, the other drops. Charless Law states that pressure and temperature are directly related. If one goes up, the other goes up with it. Lastly, Avogadros Law states that volume and pressure are directly related. If one goes down, the other drops with it. The Ideal Gas Law incorporates all three of these laws into one equation. Take a moment to think about this. The ideal gas law equation is a constant equation, meaning that it can always predict its own behavior. We currently have four variables: Pressure, Volume, Temperature, and Mass. How would you go about putting these variables together to make them related as stated here? Pause the lecture now and think on this for as long as necessary, trying to make a sample equation that you think might be the ideal gas law. Click to the next slide when ready. [Pause]14The Ideal Gas Law: PV=nTThe Ideal Gas Law states the way in which gasses interact.Since Pressure(P) and Volume(V) are inversely related, they must be on the same side of the equation.Since Temperature(T) and Pressure(P) are directly related, they must be on the opposite sides of the equation.Since Volume(V) and the mass in moles (n) are directly related, they too must be on opposite sides of our equation.Here is how the ideal Gas Laws work together. In the equation above, P represents pressure, V represents Volume, n represents the mass in moles, and T represents the temperature. Pressure and Volume need to be on the same side of the equation to inversely affect each other. 15