Keep it Bottled Up*

Teacher Version(.doc)

Student Version(.doc)

• Grade Level(s):  6th& 7th
• Primary Focus: Math; NC Standard Course of Study Areas: 6th: 1.07, 5.04; 7th: 2.02, 3.03, 4.01; 8th: 4.01, 4.02, 5.01, 5.02
  • (Key Concepts:  Pressure vs. Time Graph, Rate of Change, Slope, y-intercept, and y=mx+b )
• Secondary Focus: Science; NC Standard Course of Study Areas: 6th: 7.02; 7th: 3.01
  • (Key concepts: Temperature, Gases, Chemical Reactions, Reaction Rates, and Pressure )
• Computer/Technology Skills: Calculators, Probeware, Data Visualization; NC Standard Course of Study Areas: 6th: 3.01, 3.03, 3.06; 7th: 1.10, 3.01, 3.02
• Essential Question: What makes Effervesent tablets fizz? How do you know when a gas has been created?
• Summary of Activity: Students will use the gas pressure sensor to detect the gas that is a product of a chemical reaction.  They will test how the Effervescent tablets react in two different temperatures of water and compare the pressure vs. time plots of each.  They will then calculate and compare the slope of both experiments.
• Cognitive Teaching Strategies: Understanding the byproducts of chemical reactions can be difficult for students to conceive, especially when it is an odorless and colorless gas.  The use of the gas pressure sensor can illustrate to students that not only does the gas exist but how the gas increases throughout the chemical reaction process.  You can also demonstrate the concept with a balloon on top of the flask.  As gas is created and pressure builds, the balloon will inflate.
• Materials:
  • Gas Pressure sensor with tubing
    (1 per group)
  • TI graphing calculator (1 per group)
  • EasyLink data interface (1 per group)
  • One hole rubber stopper (included with gas pressure sensor)
  • 75 mL flask (or 125 mL)
  • Water: room temperature and warmed
  • effervescent antacid tablets (half tablets – at least 2 halves need per group)
  • Goggles
  

Procedure:

1. Obtain and wear safety goggles.
2. Turn on the calculator. Connect the Pressure Sensor to the EasyLink adapter and calculator.
3. Attach the tubing directly to the white stem of the Pressure Sensor with a gentle half-turn. Attach the other end of the tubing to a rubber stopper that tightly fits the container.  Ensure that the blue valve is in the horizontal position so that the gas cannot escape.
4. Set up EasyData for data collection.
   1. Start the EasyData application, if it is not already running.
   2. Select  from the Main screen, and then select New to reset the application.
   3. Select  from the Main screen, and then select Time Graph…
   4. Select  from the Time Graph Settings screen.
   5. Enter 0.2 as the time between samples in seconds.
   6. Select .
   7. Enter 100 as the number of samples and select .
   8. Select  to return to the Main screen.
5. You are now ready to collect pressure as a function of time data.
   1. Put 75 mL of room-temperature water in the container. In rapid sequence, put half of a tablet in the container, seal the container with the stopper, and select  to begin data collection in order to capture the start of the pressure change. Data collection will run for 20 seconds. (You may get a message to record over the previous data, select OK.)
   2. After data collection is complete, point the container away from all people and carefully remove the stopper. Discard the water and any remains of the tablet.
6. Examine the displayed graph. If you achieved a good seal between the container and stopper, you should see a uniformly increasing pressure graph. If you need to repeat data collection, select and repeat Step 6. If the run was good, select  to return to the Main screen. To store the data, select , select Store Run, and then select .
7. Now prepare to repeat the experiment with warm water.
   1. Put 75 mL of warm water in the container. In rapid sequence, put half of a tablet in the container, seal the container with the stopper, and select  to begin data collection in order to capture the start of the pressure change. (You may get a message to record over the previous data, select OK.)
   2. After data collection is complete, point the container away from all people and carefully remove the stopper. Discard the water and any remains of the tablet.
8. Examine the displayed graph. If you achieved a good seal between the container and stopper, you should see a uniformly increasing pressure graph. If you need to repeat data collection, select  and repeat Step 7.
9. Once you are satisfied with the graph, select  to return to the Main screen. Exit EasyData by selecting  from the Main screen and then selecting .
10. Next you can view both runs together.
    1. Press  [stat plot] and press  to select Plot 1.
    2. Change the Plot1 settings to match the screen shown here. Press  to select any of the settings you change. This means that the warm-water data will be plotted with the boxsymbol
       .
    3. Use the cursor keys to position the cursor back up at the top of the screen, highlighting the Plot2 icon. Press  to switch the screen to Plot2.
    4. Change the Plot2 settings to match the screen shown here. Press  to select any of the settings you change. The room-temperature water data will then be plotted with the dot  symbol.
       
    5. Press  and then select ZoomStat (use cursor keys to scroll to ZoomStat) to draw a graph with the x and y ranges set to fill the screen with data.
    6. Press  to read values off of the plots. Press  and  to trace along each plot. Switch between plots by pressing  and .

Analysis:

1. Position the cursor at the beginning of the room-temperature water plot and find the y‑intercept. Repeat for the warm-water plot. Round all values to three significant digits and record both y‑intercepts in the Data Table on the Data Collection and Analysis sheet.
• Answer Question 1 on the Data Collection and Analysis sheet.
2. Position the cursor on the room-temperature water plot. Use the cursor keys to identify two points (x1, y1) and (x2, y2) separated by at least five seconds. Record the coordinates in the Data Table on the Data Collection and Analysis sheet.
3. Switch to the warm water plot and identify two points from this line. Record the coordinates in the Data Table on the Data Collection and Analysis sheet.
4. When the coordinates of two points on a line are known, the slope of the line can be computed by finding the difference in y values divided by the difference in x values:
   
• Answer Questions 2 and 3 on the Data Collection and Analysis sheet. Use this formula to compute the slope for each plot. Record your answers in the Data Table
  .
5. Now, have the calculator plot these two lines with the data.
   1. Press .
   2. Press  to remove any existing equation.
   3. Enter the equation for the warm-water plot. For example, if the slope and intercept were 4 and 5 respectively, enter 4*x+5.
   4. Press  to move to the Y2 field, press , and enter the equation for the room-temperature plot.
   5. Press  to see the data with the model graphs superimposed.
   • Answer Questions 4–8 on the Data Collection and Analysis sheet.

Instructional Strategies:

• It can be difficult for students to multitask in this lab.  The rapid succession of dropping the tablet, putting on the stopper and then starting the data collection can be difficult to accomplish, but has a major impact on the results.  Assign jobs within the group, have one student drop the tablet and place the stopper, while another student starts the data collection.

Additional Resources for this Lesson:

• The Alka Seltzer website describes the chemical reaction that takes place in the tablets, as well as gives several experiments to use with your students.
• “How stuff works” compares the chemical reaction in using Alka Seltzer with baking powder and an acid.  Although this is most commonly illustrated by mixing vinegar and baking soda, this site illustrates why baking powder and baking soda are used to make “quick breads.”

Re-teaching and Enrichment Strategies:

• The Discovery Education Website can take this lab a step further by exploring the relationship between temperature and pressure.  Although it does not incorporate the Vernier probeware, it would be easy to use it in this lab.
• Alka Selzer Rockets are a fun way to illustrate the pressure that is created during the chemical reaction.  They take very few materials and can make an impressive visual impact.

Data Collection and Analysis:

HYPOTHESIS:

DATA:

	x1	y1	x2	y2	y-intercept	slope
Room temp water
Warm water

QUESTIONS:

1. What is the physical meaning of the y‑intercept? Why is this value nearly the same for both plots?
2. What is the physical meaning of the slopes of the pressure versus time plots?
3. The slope-intercept form of a linear equation is y = mx + b, where m is the slope of the line and b is the y-intercept. Use the information you found above to write linear equations to model the pressure versus time data:
   • Equation for room-temperature water data:
   • Equation for warm water data:
4. How well do the equations fit the data? You may wish to adjust the slope and/or intercept values slightly if you are not satisfied with the way the lines fit the data. If you adjust these values, rewrite the modeling equations below.
5. What do you think the pressure versus time plot would look like after several minutes, if the stopper were left in the container?
6. Would pressure continue to increase at a steady rate? Explain why or why not.
7. What would the pressure versus time graph look like if the stopper popped off in the middle of the data collection?
8. For a given water temperature, how do you think the plot would be affected if you used half a tablet?
9. What if you used two tablets?
10. Which plot indicates a faster rate of reaction? How can you tell?

DISCUSSION:

What makes Effervescent tablets fizz?  Explain.

*Adapted from: Brueningsen, C., Bower, B., Antinone, L., Kerner, E., Gastineau, J. E., & Cortez, W. (2005). Real World Math Made Easy: Explorations. Dallas, TX: Texas Instruments Inc.