Rationale:

The main purpose of these lessons is give students a conceptual understanding of the properties of gases.  According to the constructivist perspective, students construct their own ideas through their interactions with their environment.  Therefore, many students come into the classroom with their own conceptions of how gases behave due to their experiences.  As a result, some of the lessons on this page contain the exploration of daily phenomena to introduce and explain the behavior of gases. Although students may have ideas about how these phenomena work, students may have correct and incorrect ideas.  As a result, these lessons reflect and discuss possible misconceptions that students may have such as those in the Students' Ideas page.
The main reason why students should learn about gases through these lessons is due to the fact that although gases are not visible, they play important roles in our lives.  Therefore, students should know how gases affect their environment.  In addition, students should learn about gases because it is a fundamental unit that is included in the discipline of chemistry.  Since chemistry is a subject matter that interrelates the properties of gases to other concepts, students should know how gases behave to apply this knowledge to learn about other future concepts in chemistry.
At the completion of this unit and of these lessons, students should have a stronger background on the properties of gases and on the the concepts included in the Gases Web of Ideas.  Moreover, students should be able to communicate why and how gases influence our environment.

Materials:
 

a lot of water a soap bar iron fillings saw dust salt large heat resistant bowl empty plastic soda bottle balloons rubber bands perfume two transparent straws masking tape scissors ammonia two cotton swabs goggles 5 glass marbles clear plastic box lid from a card box overhead projector 2 widemouth gas collecting bottle with stoppers drinking straws gallon sized plastic bags 2 identical folding tables that can support the weight of the teacher (~3 feet by 6 feet)

bunsen burner pop cans hot plate tongs tons of pennies balances shoe boxes Activity 1:  How does temperature affect air? Worksheets refrigerator/freezer tempered glass bottles tissue paper coffee cans electric burners lab scales yarn helium (for balloon) hydrogen (for balloon) How to Make a Hot Air Balloon Worksheets construction paper strips glue sticks hot air popcorn poppers (~1440 watts) barometer 100g of dry ice

capillary tube, 1-mm internal diameter with mercury plug in place metric ruler thermometers stirrers ring stand iron ring test tube clamp rubber stopper, 1-hole wire gauze 400-mL beaker paper bags copper or plastic  pipewood dowel tape note cards 100 mL graduated cylinder 1000mL beaker disposable butane lighter hammer 1 Boiled Egg without its shell Matches plastic bag with tie 9M HCl

Conceptual Space of Activities:

This unit is developed such that it encompasses all of the concepts on the Gases Web of Ideas.  Therefore, the unit starts of with reviewing concepts such as the phases of matter and moves into gases and the kinetic molecular theory.  Once students have a been exposed to these concepts, students will be able to apply this knowledge and review and learn more about the concepts of the Four Variables:  Temperature, Pressure, Volume, and Moles.  Once students have been covered this material, the students should move onto the multiple gas laws and the main gas law which is the ideal gas law.  Then, students should look at how gases react by looking at chemical reactions and stoichiometry.

Instructional Objectives:

1.  Students will be able to distinguish between real and ideal gases.
2.  Students will be able to predict the effect of changes in pressure and temperature on the volume of a gas.
3.  Students will be able to apply their knowledge of the kinetic-molecular theory to understand the gas laws.
4.  Students will be able to describe each of the following characteristic properties of gases: expansion, density, compressibility, and diffusion.

Conducting the activities:

Lesson 1:  Gases and the Kinetic Molecular Theory

To start of the lesson, the students will work in groups and review the phases of matter by doing Activity #1 which involves classifying different substances such as water, soap, iron fillings, saw dust, salt, and others into the three phases of matter.  Then, the teacher should ask students about their background knowledge of gases and how they differ from other states of phases of matter.  Then, the teacher should begin to focus on the properties of gases by asking students why hot air rises.  Then, the teacher can perform Demo #1 which shows that gas particles can be easily compressed and expanded, which accounts for the phenomena of why hot air rises.

Results from Demo #1 that the instructor should discuss with the students:  Expanding air inside the bottle causes the balloon to inflate.  the air inside the bottle was first cooled by the ice water.  This air was trapped inside the bottle by the balloon.  The air was then heated by the hot water.  As it is heated, the air expanded or it took up more space, volume and entered the balloon.  Expanding air becomes lighter and rises.  A discussion of this idea can be explained by the ideas concerning assumption #1 of the kinetic molecular theory without explicitly stating that it is the kinetic-molecular theory.

The teacher should start the class by opening a container of ammonia or a bottle of perfume (without letting the students see) to introduce the kinetic molecular theory. Hopefully, one of the students will smell the ammonia or perfume and ask what is the odor in the room.  This will then lead to the concept of diffusion.  This will then lead into the idea that gases have particles that are always in random motion which is explained by the kinetic molecular theory.  After the teacher discusses the assumptions of the kinetic molecular theory, the teacher can perform the Demo #2: The Molecular Race Demo can to lead into the discussion of the diffusion of gases.

The purpose for the Molecular Race Demo is to allow students to compare and explain the relative diffusion rates of ammonia and hydrogen chloride gases qualitatively.  If the demonstration is performed correctly, the ammonia will diffuse about 1.5 times father than the hydrogen chloride in the same period of time.  As a result, teachers and students should actively discuss this demo and come to the conclusion that NH₃ molecules diffuse faster than HCl molecules.  They should also discuss how the NH₃ molecules have a lower molecular mass than the HCl molecules and because both molecules have the same average kinetic energy at the same temperature, move at a higher average velocity.

After students have been introduced to the kinetic molecular theory, the teacher should explain that this theory best describes ideal gases.  This can lead into the discussion of noble gases and how why they are considered ideal gases.  The teacher should also discuss why the kinetic-molecular theory does not perfectly describe the characteristics of real gases.  This day should also involve the discussion of why it is important that students know the difference between the characteristics of real and ideal gases.  These two ideas are discussed within the pages of real gases and ideal gases.

For the most part, students have a hard time understanding the kinetic-molecular theory.  As a result, the following demonstration, Demo# 3:  Kinetic Theory Made Visible, should be used to present student with a mental model of molecular motion.  As you are doing the demonstration, discuss how this demonstration presents a mental model of the kinetic-molecular theory.
 

Lesson 2:  The Four Gas Law Variables:  Temperature, Pressure, Volume, and Moles

One of the misconceptions that students have about gases is that air does not exert pressure.  Activity #2:  Up, Up, and Away! shows that air exert pressure.  To start the activity, the instructor should ask students:  Do you think it is possible to lift a teacher on a table supported by confined air?  Then, students and the teacher should do the activity which show that air pressure applied to a large area has a tremendous force.

Possible post activity discussion questions:

• If you had a table large enough and enough bags, would you be able to lift an elephant?
• As the table is lifted, what happens to the area where each individual bag touches the table?
• What happens to the total area where bags touch the table?
• Why do you think the  table stops rising even thought you keep blowing into the straw?

Conclusion:
After doing this fun activity, the students should understand that while each student is blowing air that does not press very hard against their own inside of the bag, there is a very large area for the air to press against when a lot of bags work together.

After students do the activity, the instructor can discuss how overturned trucks and cars can be turned upright by using this same idea.  Then, the teacher and the students should engage in a post discussion that leads into the idea that gas pressure is created by the molecules of the gas hitting the walls of the container.  Another concept that can be explained in this section is atmospheric pressure by first doing Demo #4: Egg in the Bottle and discussing the ideas in the page, How does the egg in the Egg In the Bottle Demonstration?.  You could also discuss the ideas in the phenomena page titled: Crushing Can-Why does the can collapse?
 
 

To start the class, the teacher can ask the question:  How do we measure the amount of gas?  For the most part, students will say that you can use grams, but the instructor should emphasize that moles are commonly used to measure gases.  To introduce students to moles, students can perform Activity #3:Counting by Weighing.  This activity gives students the opportunity to learn about stoichiometry and why we use moles.  This will then lead to the idea of molar volume and Avogadro's Law.

For the most part, all students should understand what the term volume means.  As a result, this day should involve reviewing that volume is basically the three-dimensional space enclosed by the container walls and how it is measured.  Then, the instructor should ask students why gases should be enclosed in containers that have no openings.

Since, the concept of volume will mostly be review, the instructor could use this day to assess the learning of the students of the topics that have been covered in the unit.

To start off the lesson, ask the students the question: What does temperature measure?  Then lead into the idea that temperature is essentially the measurement of the energy of a material's molecules.  The instructor should also discuss that temperature is not a direct measurement of heat of an object.  The instructor should emphasize that the temperature of gases are usually measured in Kelvin.  Moreover, the instructor should spend some time showing students how to convert from degrees Celsius to Kelvin and vice versa. Most importantly, the teacher should discuss that when gas molecules are heated that the spacing of the molecules not the size of the molecules are increasing which is one of the misconceptions that students may have such as discussed in the students' ideas page. Also, the instructor should discuss how Kelvin temperature of a gas is directly proportional to its kinetic energy.  In addition, the teacher should discuss Gay Lussac's Law at this time.  A phenomena that also can be discussed at this time is Why does popcorn pop?, as well as fun being a treat for the students!

Lesson #3:  Focus lesson

The activities and demonstration in this lesson are based on concepts that are within the Gases Web of Ideas.  The first activity is based on the concepts of temperature, Charles's Law, density, volume, kinetic-molecular theory, and pressure.  Although this activity does not involve students learning about how the relationship of temperature and volume  as Charles's Law, they are constructing a meaningful, conceptual understanding of how a change in temperature of a gas also affects the volume of the gas. Moreover, this conceptual understanding will help them later on in the unit to think about how the variables change instead of using a simple algorithmic of plugging in numbers into a memorized equation. The second part of this lesson involves students applying their findings in the first activity to the density of gases.  The density of gases and how they affect the properties of gases is also included in the gases web of ideas.  The second activity involves students applying their knowledge from the first activity and demonstration to construct their own hot air balloon which is a discussed in the phenomena that involves gases.  To find out more about hot air balloons, click here:How do hot air balloons work?.

For this day, students will get the opportunity to learn more about Charles's Law by watching the teacher give a quantitative Demo #5:Charles's Law  concerning Charles' Law.

Possible discussion could be focused on how the focus lesson relates to this demonstration and why does this demonstration show Charles' Law.

This class should be started by showing the Cartesian Diver which qualitatively shows the relationship between pressure and volume.  While some students make see that these variables are inversely proportional from the demo itself, it is important that the teacher discusses the material on the Cartesian Diver page.

Some questions that can be asked are the following:

What causes the diver to rise and fall?
What is the relationship between temperature and gas volume in the dropper when it is in an uncapped container?
What quantity is held nearly constant by using an uncapped container?  Why is this important?

The instructor should start the class by doing Demo #6: Molar Volume.  The purpose of this demo is to demonstrate the molar volume of a gas.  This will then lead into a discussion of Avogadro's Law.

Results of demo #6:  The garbage bag inflates slowly as the solid CO₂ sublimes.

One of the lessons that I found on the internet was called:MTV no PTV lesson.  I have chosen to make a direct link to this page because I think that it is a lesson that is really good and does not need to be altered.  In this lesson the interdependence of three variables of pressure, temperature, and volume are reviewed.  In this lesson, students have the opportunity to engage in an activity that allows them to see more ways of how pressure, temperature, and volume are related with respect to gases.  Students will also be introduced to a method of how to remember which relationships are directly and inversely proportional.

Now that students have had multiple examples of how pressure, temperature, volume, and moles are interrelated, students can be introduced to the value of R and the Ideal Gas Law.  The instructor can introduce the value of R by doing Demo #7:  The Value of R.

Possible questions that could be discussed are below:

What unit of volume, tempter, and pressure must be used in the equation?
What is the theoretical value of R?

Week 4

Unit Exam on Gases

Extensions:

    There are many extensions that are possible for these lessons.  First of all, all of the demonstrations can be done by the students if the teacher modifies them by constructing procedures that allow students to work in groups.  Another possibility to extend this lesson is to explore other phenomena such as scuba diving, submarines, and the ammonia fountain.  Students could be assigned to find other phenomena that involve gases and write papers that they could present to the class.  Another extension that could be made to this lesson is to have students do more quantitative labs to better understand the gas laws.  Since my goals were to get to students to get a strong conceptual understanding of gases, very few of these types of lessons were included in this series of lessons.

Expectations:

Students will demonstrate their understanding of gases through different forms of assessments. The main form of assessment that will be used is anecdotal recordings and formative.  They will also be asked questions during discussions and will be asked to turn them in so that I can evaluate if they are meeting the learning objectives.  In the focus lesson, I have included a quiz that will also be graded to evaluate my students' learning.  The summative form of assessment will be based on a unit exam that will have questions similar to the Possible Unit Exam Questions that all students will take at the end of the unit.