Exploring Gas Behavior

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Objective

Student will be able to justify which factors affect pressure through performing a computer activity and be able to visualize the relationship between pressure, volume, and temperature through graphing.

Big Idea

Gases have certain temperature, number of moles, volume, and pressure which are all related variables. When one of these variables change, there is a characteristic effect on the other variables.

Introduction

In this lesson students have a chance to start to explore gas laws though performing two different computer activities.  In particular the goal is for them to begin to understand the relationships between pressure, volume, temperature, and number of particles.  Additionally, students practice graphing the relationship between gases through a graphing activity.

  • This lesson does not align with any specific NGSS Performance Expectation; however, it does align with the old California State Standards.  Additionally, I feel that understanding gas laws and the basics of earth's atmosphere are important for students to know and is a topic that is interesting and fun for students.
  • This lesson aligns with the Next Generation Science and Engineering Practice 2: Developing and Using Models.  It does so because students are able to visualize computer models that show gas particles and how pressure, volume, temperature, and number of particles are related.
  • This lesson also aligns with the Next Generation Science and Engineering Practice 4: Analyzing and Interpreting Data.  It does so because students are graphing data and analyzing the data for the type of relationships.
  • This lesson aligns with the Next Generation Crosscutting Concept 3: Scale, Proportion, and Quantity.  It does so because students are challenged to think about gases, despite the fact that they cannot see them.

For this lesson the only resource needed is access to computers.

Explain

5 minutes

I begin by prepping students for the lesson.

  1. I first pass out the two papers to students including the Gas Laws Graphing Activity and Gas Laws Computer Activities.
  2. I then go over the goal of the lesson is to, "learn about the variables related to gas behavior".
  3. I then tell students that they will be first start by working on the two computer activities and that when they are done they will do the graphing activity.  I tell them that they must work in their groups for the computer activity, but they can work either by themselves or with their partners when they are graphing.

Explore

45 minutes

For the first part of the lesson I give students time to begin to think about the variables involved in gas behavior through performing two different computer activities on their Gas Laws Computer Activities paper.

1. Students are first doing a PhET activity where they are looking at the variables involved with gases by trying to get the top to pop off of the container.

  • The goal is for them to see that adding heat, decreasing the volume, or adding more particles will cause the top to pop off. 
  • This movie explains how the activity works. 
  • Although my goal was for students to see how temperature, number of particles, and volume affect pressure, not all students saw this.  For the most part at least students were visualizing gas behavior and all students at least saw that increasing temperature made the top pop off.
  • Here are some examples of student work.
    • Student 1: In this first student example you can see how the student realized that they were changing temperature, pressure, and volume as parameters to get the lid to pop off, but then in their explanation only talked about heat as a factor to increase pressure.  Additionally for the second part of the activity the student didn't get the correct relationships for temperature/volume or volume/pressure.
    • Student 2: In this second example of student work I am not sure that they student actually got the top to pop off.  The student did see factors that affect pressure which is evident in their explanation of "compact of space" as volume, "release of particles" and particles, and "temperature change".  Additionally this student did not write in the relationships of the variables on the second page and got the relationship between temperature and volume incorrect.
    • Student 3: In this last example of student work the student seemed to really just look at the variables of pressure and temperature.  This is evident in their explanation where they just discussed how temperature impacts pressure.  Also on the second part of the activity the student missed two of the relationships of the variables.
    • Based on the student work I realize that many students were stuck with the type of relationship of the variables on the second part of the activity so I will need to do a better job of explaining the relationships while students are learning the laws in the next few lessons.  Also, next year when students are doing this activity I will need to make sure to help students more at their stations so they understand what they are holding constant and then looking for increase/decrease of the variables.

2. For the second activity students are going onto a computer site that more directly tells them about the variables involved in gas laws and gives them the specifics about Boyle's Law. 

  • This site is much more straight forward and students definitely understand the variables involved in Boyle's law, the constants, and the type of relationship between pressure and volume.
  • Most students work looked the same for this activity as that it was so straightforward.  Here is an example paper.  The answers to this computer activity are on the bottom of the second page.

Elaborate

30 minutes

For the last section of this lesson I had students perform a Gas Laws Graphing Activity

  • In this activity students are graphing data for Boyle's and Charles' Laws and then comparing the graphs. 
  • The goal is for them to see how Boyle's Law is an inverse relationship while Charles' Law is a direct relationship.
  • Students have various degrees of graphing experience so I make sure to help them set up the first graph for Boyle's Law to remind them about labeling their axis, setting up the values for the axis, titling their graphs, and plotting points.
    • I tell students that the x-axis always has the independent variable and the y-axis has the dependent variable.
    • I tell students that the title of their graph is always the y-variable versus the x-variable.
    • When students are setting up the values for their axis I tell them to look at the highest number and lowest number to see the difference needed for graphing.  They then should count the number of squares and divide by the difference to see how much value each line should be worth (for example if the range of data is 0 to 100 and there are 20 squares then since 100/20= 5 each square should be worth 5).
    • Finally I help them with making sure to do a dot-graph rather than a bar graph.
  • Here is an example of one student's graph.