AACT MemberOnly Content
You have to be an AACT member to access this content, but good news: anyone can join!
Summary
In this unit, students will investigate gases similar to how scientists learned about them “back in the day.” Students begin by investigating gas behavior, then they investigate gas density and use this to interpret Avogadro’s hypothesis that gases under the same conditions combine in simple whole number ratios. This unit plan was created by W. Patrick Cunningham of CT Johnson High School in San Antonio, Texas. Read his Chemistry Solutions article for more information about this unit.
Grade Level
High school
Objectives
By the end of this unit, students should be able to
 Understand the relationship between temperature, volume, and pressure of gases.
 Recognize that gases have mass and therefore density.
 Realize that gas particles are different sizes, which is what effects their density.
Chemistry Topics
This lesson supports students’ understanding of
 Gases
 Density
Time
Teacher Preparation: See individual activities
Lesson: Seven class periods
Materials
 Refer to individual activities
Safety
Always wear safety goggles when working with chemicals in the lab.
Teacher Notes & Downloads
Lesson 1 
Students qualitatively become acquainted with the gas laws. 
Lesson 2 
Students interpret results from gas law investigation to determine temperature, pressure, and volume relationships, which provokes the idea of gas having density.

Lesson 3 
Students quantitatively investigate gas densities.

Lesson 4 
Students become more familiar with the concept of gas density on the microscopic level.

Lesson 5  Students investigate gas compressibility to collect data and lead them to determine which density theory is correct.

Lesson 6 
Students use their results from the Boyle’s Law lab deduce which of the two density theories is correct.

Lesson 7  Once students have come to the conclusion that the highermass particles theory best explains differing gas densities, they watch a video about the law of combining volumes and Avogadro’s hypothesis.
