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Understanding how gases behave under different conditions is not just crucial for chemistry class—it is knowledge that applies to many real-world situations, from predicting weather patterns to optimizing car engines. As the new school year begins, it’s the perfect time to introduce students to—or refresh their understanding of—the four fundamental gas laws: Boyle’s law, Gay‑Lussac’s law, Charles’ law, and Avogadro’s law. Teaching about these laws not only helps students understand the relationship among gases’ different properties, but also helps them develop the fundamental knowledge needed to progress into more advanced chemistry concepts, such as thermodynamics and kinetics, later in the school year.

One easy, engaging way to give a comprehensive overview is with our multi-part experiment, “Exploring the Properties of Gases” using the Go Direct^{®} Gas Pressure Sensor. In this experiment, students engage in four distinct investigations, each focused on one of the gas laws. As they collect, analyze, and interpret data on pressure, volume, temperature, and number of molecules, students deepen their understanding of the behavior of gases, both qualitatively and mathematically.

## Exploring the Properties of Gases

**Objectives**

- Conduct a set of experiments, each of which illustrates a gas law.
- Gather data to identify the gas law described by each activity.
- Complete the calculations necessary to evaluate the gas law in each activity.

**What You Need**

- Vernier Graphical Analysis
^{®}app - Chromebook™, computer, or mobile device
- Go Direct Gas Pressure Sensor
- 20 mL gas syringe
- Plastic tubing with two Luer-lock connectors
- Rubber stopper assembly with two-way valve

- Go Direct Temperature Probe
- Stir Station
- Electrode Support
- Large-volume container for water bath (at least 10 cm in diameter and 25 cm tall)
- 125 mL Erlenmeyer flask
- 100 mL graduated cylinder
- Hot-water supply (up to 50°C) or hot plate
- Ice

## Boyle’s Law: Pressure *vs*. Volume

In the the first quick and easy experiment of “Exploring the Properties of Gases,” students examine the mathematical relationship between the pressure and volume of a confined gas at a constant temperature.

First, students set a measured volume of air into the barrel of a 20 mL syringe. They then insert the syringe into the Go Direct Gas Pressure Sensor and launch Graphical Analysis on their Chromebook or other device to start collecting pressure data. Throughout the activity, students adjust the piston to see how different volume levels impact the pressure exerted by the confined gas. They then use their results to predict pressure at other volumes.

For the best results, we always recommend students collecting—and analyzing—at least six data points.

## Gay-Lussac’s Law: Pressure *vs*. Absolute Temperature

Next, students investigate the relationship between the absolute temperature of a gas and the pressure it exerts by testing an Erlenmeyer flask containing an air sample in water baths of varying temperatures. Students collect data using a Go Direct Gas Pressure Sensor, as well as a Go Direct Temperature Probe, as they experiment with water baths of temperatures ranging from ice cold to approximately 60°C.

During this experiment, students practice analyzing data and graphs as they determine the mathematical relationship between the absolute temperature of a gas sample and the pressure it exerts, which is the basis for Gay‑Lussac’s law.

As an extension, students can use their data to find a value for absolute zero on the Celsius temperature scale.

## Charles’ Law: Volume *vs*. Absolute Temperature

In the third experiment, students** **study the relationship between the volume of a gas sample and its absolute temperature as they explore Charles’ law. This activity involves a similar apparatus as Gay‑Lussac’s law, with the addition of a syringe that attaches to the Erlenmeyer flask.

As students collect and analyze temperature data, it is important for them to know the total volume of air in the flask and the syringe. They can figure this out by using a graduated cylinder to accurately measure the volume of the flask (up to the bottom of the rubber stopper).

Students use the Go Direct Gas Pressure Sensor to monitor the pressure level in the system so they can ensure constant pressure throughout data collection.

## Avogadro’s Law: Pressure *vs*. Number of Molecules

Finally, students study the relationship between the number of molecules in a gas sample and the pressure it exerts as it relates to Avogadro’s hypothesis which states that, “Equal volumes of gases, at the same temperature and pressure, contain equal numbers of molecules.”

During this data‑collection experiment, students use the same setup as the one used for Charles’ law, although the water bath and temperature probe are optional. It is important to keep the temperature and volume constant throughout this experiment, so that students can assume that gas volume is proportional to the number of molecules.

While collecting data, instead of entering a total number of molecules, students enter a total volume of gas that has been compressed into the flask (for example, 120 mL worth of molecules can be entered as 120 molecules) and then analyze their results.

## Putting It All Together

After completing these experiments, you can ask students to write an equation using the two variables and a proportionality constant (*k*), calculate the constant, and explain—in their own words—how their findings describe each of the four gas laws. The four gas laws covered in this series of experiments can serve as a good review of concepts that students will likely see again in an Advanced Placement (AP), International Baccalaureate (IB), or college general chemistry courses.

Beyond investigating basic gas laws, students can go on to use the versatile Go Direct Gas Pressure Sensor to explore real-world applications, like studying sugar fermentation in yeast or evaluating the effect of acid rain on stone structures.

Looking for more? Check out our “Gas Laws in a Jiffy” webinar, which walks through these activities and provides additional tips and tricks to help teach students about gas laws.

Questions? We’re here to help! Reach out to chemistry@vernier.com or drop us a question in our live chat! Explore our chemistry page for more data-collection technology designed to help students explore the chemistry behind real-world phenomena.

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