gas laws written on a black chalkboard

Everything You Need to Know About How to Teach Gas Laws

Reading Time: 4 minutes

Most of my first-year chemistry students are sophomores, which typically means they have just started or are about to start driving. Others have bikes or have to take care of smaller siblings’ bikes. So throughout this unit, we discuss tires. Tire pressure and the importance of having your tires inflated enough to drive/ride safely. This unit usually falls during the winter months- so we can also talk about how cold temperatures seem to reduce tire pressure and how adding more air increases the pressure and volume of the tires. I often get questions like 

  • What if we over-inflate? Can the tire explode? 
  • Can you cause a car accident by not filling up your tire’s enough?
  • If you fill up your tires in the winter, does that mean they’ll be too full in the summer?
  • How do you know if your tire has a leak vs just being too cold?

Lots of real-world applications in this unit. Almost all of the kids are into it, but especially those kiddos who are really into cars or bikes. They are confident in their understanding of tire pressure, which bleeds into the rest of the discussions. I love seeing kids who’ve struggled to connect with chemistry finally find something that pulls them in!

Gas Laws Lesson Plans

Total Duration: 10.5-17 days

Note: a day refers to 45-50 minute periods.

Topic & TimelineTasksDescription
Gas Relationships
2-3 days		Gas Law Inquiry Station Lab

Whiteboard Discussion		You can set up a wide variety of quick gas law activities. Here are the ones I like the most:
V vs n – balloon races with baking soda and vinegar
P vs T – Candle demo 
P vs T – Can Crush
P vs V – Cartesian Diver
P vs V – balloon/marshmallow in a syringe
T vs V – balloon in hot vs cold water
T vs V – for this balloon race, place water in a flask and seal it with a balloon. Heat the flask until the balloon rises. Move the flask to an ice water bath and see the balloon deflate. 

I have my students record their observations: what changes did they make, and how did the system react? Did any of the gas variables stay constant? What’s happing to the particles in the system we’re studying? 

I’ve done this lab in several ways, and it always comes down to time:

More Time?
-All students complete all stations
-All students complete particle diagrams for all stations

Less Time?
-Each group completes one station
-They present their findings to the class
-Each presentation includes a demo so that all students can observe the phenomena

Even less time?
-Complete the stations as demos during notes
-Have a thorough discussion about how each relationship is affected by the changes that were made as well as what was held constant
Gas Behavior
0.5 – 1 day		*KMT if you haven’t already
!
Gas Variables

Converting Pressure + Temperature Units		After learning about the gas law relationships and discussing our observations, I like to take a break to discuss the four variables: Pressure, Volume, Temperature, and Amount. If you haven’t already discussed the Kinetic Molecular Theory with your students, now’s the time to do it!

You can start your Gas Law Unit with this discussion before the Inquiry Lab if you’d like your students to have more vocabulary before diving into the gas relationships. 
After discussing the variables, I have my students practice converting between pressure (atm, kPa, torr) and temperature units (F, C, and K). 
Boyle’s, Charles, Gay-Lussac, and Avogadro’s Laws
2-4 days		Gas Laws Notes + Practice

Practice Problems		We discuss each law, often referring to our observations from the inquiry lab. Sometimes I show a clip from a demo video to help jog their memories. 

I like to get through all four gas laws in one day. I focus on the relationships (not the names) and identifying what’s being held constant. So, one day of notes/discussion. One or two days of practicing with mixed problems. I have colleagues who prefer to complete one gas law a day. They complete a demo followed by notes and practice problems. I think both approaches are perfectly fine. Do what makes the most sense to you!
Combined Gas Law
1 day		Combined Gas Law Notes

Practice Problems		After masting the individual gas laws, I show my students the combined gas law and how every gas law we’ve seen so far contributes to it. So no, we don’t need to memorize the four gas law equations because they’re all here! I prefer using the combined gas law that includes moles (n). We’ve been talking about it up until now, so I think it’s a bit weird to remove it now. My colleagues prefer not to because it’s easier for kids to identify when to use the Ideal Gas Law. I think this is silly – either the system changed from STP, or it didn’t. But again, choose what makes the most sense to you.
Ideal Gas Law
1 day		Ideal Gas Law Notes

Practice Problems		The Ideal Gas law works because one side of the Combined Gas Law is set to standard units. So, I like to show my students how the R constant came about- so we solve for R as a bell work. Then we discuss how R would change using a different pressure unit. I say, “wouldn’t it be great to have an equation we can use in place of the combined gas law when something changes from STP?” Boom! The Ideal Gas Law is now a shortcut, and they are on board. Fewer variables to keep track of? Yes, please!
Ideal Gas Law Lab
1 day		Popcorn LabHow much pressure is required to pop popcorn? I like to perform this lab and point out that microwaves have to change many conditions to prepare this treat for them. If you have a microwave available, you can even encourage your students to bring in a bag for them to snack on while completing their calculations. 
Partial Pressure
0-1 day		Partial Pressure Notes
Practice Problems		I’ll be honest. Partial pressure is not in my state standards, so most years, I skip it. But it is a pretty straight forward topic, and in the years I’ve been able to include it, it’s gone pretty smoothly. Again, I refer to tire pressure in winter. When my tire pressure is low, I add more particles of gas. The new gas has an additive effect on the pressure. 
Optional: Gas Stoichiometry
1-2 days		Molar Volume of a Gas Lab

Gas Stoichiometry

Practice Problems		Got more time? Tie in stoichiometry! I typically do this lab as a demo because I don’t have enough appropriate equipment for each group. We collect the gas produced and determine how much gas should have been collected using both stoichiometry and the ideal gas law. 
Review1-2 DaysVocabulary Review

Study Guide		Have your students practice with vocabulary, but also give them lots of real-world examples in their study guide (or review game). 
Assessment

Further Reading

The Chemistry Particle’s Guide to Teaching High School Chemistry, The Chemistry Particle

Gas Laws Notes Bundle, TeachersPayTeachers

Gas Laws with Daniel Radoff – ChemEdExchange

Gas Laws – Chem Demos, University of Oregon

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