Gas Laws Lab

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Objective

Student will be able to synthesize their knowledge of gases to analyze the behavior of gases through performing eight different activities in a lab.

Big Idea

Gases behave in characteristic manners which can be seen in many different phenomena.

Introduction

In this lesson students continue their learning about gas laws by performing eight different experiments which challenge them to think about why phenomena related to gas behavior occur.

  • 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 challenged to come up with models of how gases are behaving within the various experiments.
  • This lesson also aligns with the Next Generation Science and Engineering Practice 3: Planning and Carrying Out Investigations. It does so because students are performing eight different experiments to learn about how gases behave.
  • This lesson also aligns with the Next Generation Science and Engineering Practice 6: Constructing Explanations and Designing Solutions.  It does so because students are challenged to try to explain why the different phenomenon occur in the experiments.
  • 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 and try to understand the relationships between the variables.

For this lesson there are several resources needed for each of the stations:

  1. For Station #1: hot plate, soda can (one per group), tongs, ice water, graduated cylinder, water bottle, and goggles.
  2. For Station #2: one big beaker (500mL) and one small beaker (100mL)
  3. For Station #3: beaker (250mL), straws cut in half in a plastic bag labeled clean straws, and a beaker (250mL) labeled waste straws.
  4. For Station #4: 2L bottle, bag of straws labeled clean, bag of balloons labeled clean, and a waste beaker (250mL) labeled waste straws and balloons.
  5. For Station #5: a microscale bell jar (available from flinn scientific), and a bag of marshmallows (one per group)
  6. For Station #6: a 2L bottle, a thermometer (that fits inside the bottle), and a fizzkeeper.
  7. For Station #7: a candle, clay, tin plate, water, food coloring, and a 250 mL graduated cylinder (plastic preferred).
  8. For Station #8: a glass jar (mason jars are great!), a piece of paper, Styrofoam, or plastic (I cut a circle out of a plastic or Sytrofoam plate).

Explain

15 minutes

I begin the lesson by explaining the lab to students as detailed below. 

  • First I pass out the Gas Laws Lab to students and have them briefly skim for five minutes.
  • I then review the goal of the lab to students as learning how gases behave through performing investigations.
  • After this I spend time going through what students will be doing at each station.  I give a quick summary for each making sure to include important safety details and highlight areas where students get confused.  This video shows the setup and procedures for each of the labs.
    1. For station #1 I tell them to make sure that the water in the can is boiling and a lot of vapor is coming out of the can.  I also tell them to make sure that the water in the beaker is cold and to add ice to make sure its very cold. I then demonstrate how to take the can with the tongs and quickly flip upside down into the cold water.  See the video to get a better understanding of how this works.
    2. For station #2 I tell them that they are simply placing the smaller beaker upside down into the larger beaker of water.
    3. For station #3 I show students where to get the clean straws and place the discarded straws.  I also tell them to make sure to hold one straw perpendicular to the other and to make sure to get low.  See the video which shows a student doing the activity to get a better understanding of how to do this.
    4. For station #4 I make sure to show show students where to get the clean straws and balloons and tell them to make sure to discard them in the waste when they are done.  I make sure to explain that when they are trying to blow up the balloon with the straw that they are still only having their mouth on the balloon and that the straw hangs on the side of the balloon going into the bottle.
    5. For station #5 I go over how to use the microscale bell jar, and let students know to grab a fresh marshmallow from the bag and to throw their marshmallow away when they are done.
    6. For station #6 I tell them that we will be doing it as a demo.
    7. For station #7 I tell students to be careful when lighting the candle and if its hard to light to make sure it is dry.  I then show them how to put the graduated cylinder over the candle.  See the video to see how this is done.
    8. For station #8 I warn students that this is a wet station and to keep their papers away from the bucket.  I then show them how they are going to be filling the jar with water, placing the piece of paper on it and then turning upside down.  I explain that when they take their hand away that the paper should stay.  See the video of what this should look like.
  • I find that students have a hard time getting the thermometer to change on station 6 with the fizzkeeper so I choose to do that one as a demonstration to make sure students understand what I expect of them.  To do this I put the lab on the document camera so that they can see station #6 and have them turn their papers to station #6.  I then lead them through the protocol by putting the thermometer inside the 2L bottle, recording the initial temperature, pumping up the bottle with the fizzkeeper and then recording the final temperature.  The bottle definitely gets firm when its pumped, but the temperature usually only changes by a degree or two because of the small amount of gas.  I make sure to model how students should draw the gases and show arrows for pressure.
  • I then break students into cooperative groups.  To do this I use a deck of cards with numbers Ace through 7 or 8 (depending on the size of the class).  I then have students go to lab stations based on their numbers Ace's to one table, two's to another table, etc.  This year i made sure to only have 7 groups because I had them skip station #6 as that we did that as a class.  Then, based on students suit they are responsible for a role.  I tell them to rotate roles at each station.  For more details on how I do cooperative groups in my classroom see my reflection in my Unit 1 Density lesson.

Elaborate

60 minutes

For this part of the lesson students are completing the Gas Laws Lab

I have students go to their assigned lab stations and let them know that they will be spending 5 minutes at each station and then rotating. 

  • I tell them to make sure to get the experiment done, and then answer the questions to the best of their ability.  
  • I let them know that some stations are quicker than others so if they are done early to make sure that they are drawing proper models and answering the questions completely.
  • I also tell students that when they are thinking about why the phenomenon occur to keep in mind that water flows from more pressure to less pressure.
  • I then begin the timer in the front of the classroom on the projector (I use a countdown timer from TimerTools).  I have the timer go for 5 minutes.
  • While students are working for the 5 minutes I walk around and help out groups.  I make sure that students are working well as a group and helping each other.  I also answer questions students may have.
  • When the timer is getting close to 0s I let students know to start cleaning up.  Then, when the timer goes off I tell them to rotate.  I also let them know if they get to a station and it is messy that they should make the last group go back.
  • I then restart the timer.  I continue this procedure until groups have done all 7 stations.
  • As students are getting done with their last station I tell them that they can go back to a station if they want to try it again, and then to complete the conclusion for their lab.
  • As students complete their labs I have them turn into my basket.

Evaluate

I grade students labs using a gas laws lab rubric

These are some examples of students graded labs.

  • Student example 1: In this first example the student does a great job with her models to explain why the phenomenon occur in the different experiments.  She did however miss a point because she didn't really discuss a source of error specific to an experiment.
  • Student example 2: In this second example the student missed points that are characteristic of many of his classmates.  He did not explain the gas laws or relationships in experiment 5 or 7 and did not even try to explain why the water stayed up in station #8.   I gave this student all of his points for his conclusion, but again it was not a very good source of error or how it would effect the results of the lab.
  • Student example 3: In this third example the student earned all of their points.  If you notice in station #2 they talk about air by saying oxygen.  This is a common misconception that I see among many students that they assume that air is oxygen.  I try to explain to them that air is mixture of gases and is actually mostly nitrogen, but they continue to hold onto this misconception.  This student also has a good conclusion and a viable source of error.
  • Student example 4: In this fourth example the student earned all of her points.  I included this example because she had really good drawings which shows that it is nice to have this type of lab for students who are good artists to have a chance to showcase their talents.