Summary

In this lab, students determine the relationship between volume and pressure of a gas and its temperature. This lab also addresses the misconception that air does not have mass or density by having students determine the mass and density of air pumped into a bottle.

Grade Level

Middle School, High school

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

• MS-PS1-1:Develop models to describe atomic composition of simple molecules and extended structures.
• HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative positions of particles (objects).
• Scientific and Engineering Practices:
  • Using Mathematics and Computational Thinking
  • Developing and Using Models
  • Analyzing and Interpreting Data

Objectives

By the end of this lesson, students should be able to understand:

• that air has mass and density
• the relationship of pressure and temperature for gases

Chemistry Topics

This lesson supports students’ understanding of

• Gas laws
  
• Matter
• Density
  

Time

Teacher Preparation: 10 minutes
Lesson: 30–40 minutes

Materials

• Two 2-L bottles
• One cap for bottle
• One Fizz Keeper
• Two aquarium thermometers
• Balance

Safety

• When you are done, ask the teacher to release the pressure on the bottle – do not do it yourself!
• Always wear safety goggles when working in a chemistry lab.

Teacher Notes

• Flinn includes a lab using the Fizz Keeper to show the relationship between temperature and volume (or pressure) of a gas. I find that my students often think that air has no mass and no density, so I adapted this lab to address that misconception.
  • Sometimes the Fizz Keeper pump seems to depress without offering any resistance, thus not pumping any air into the bottle.Do not count those as one of your “pumps.”
• You may want to ask students to bring in a 2L bottle from home, giving them a deadline of several days before the experiment, or collect bottles from your own use, from other faculty, etc.
• The thermometer you get may vary – tweak the instructions about how to read the thermometer as appropriate. If you do not get a stick-on/adhesive aquarium thermometer, you might consider placing the thermometer on the inside of the bottle. You also might need to help student in interpreting the readings, since sometimes the color changes subtly and you may have to make your best estimate. Here is a guide on how to read the aquarium thermometers:
  
• It might be helpful to review the properties of gases and how to calculate density (D = m/V) at the beginning of this lab, particularly reminding them that gases can be compressed or can expand to fill the space available to them (in this case, the 2-L bottle). This will help students answer the last two analysis questions, as they may forget that the final volume of air is the volume of the container (2 L).
• To scaffold some of the analysis questions, you can add hints, such as a reminder in #4 that the answer can be calculated from the final mass of the pump bottle minus the initial mass of the pump bottle, in #5 and #7 that the volume of the gas is the volume of the bottle, or in #6 that the answer is the mass of air originally in the bottle plus the air that was added (#4 + #5).