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Plop, Plop, Fizz Fast: The Effect of Temperature on Reaction Time

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Abstract

Alka-Seltzer® tablets fizzle furiously when dropped into water. The moment the tablet starts dissolving, a chemical reaction occurs that releases carbon dioxide gas. In this science project, you can even measure how long and loudly your tablet fizzes using a smartphone equipped with a sensor app. Do you think you can make Alka-Seltzer fizz faster or more loudly by changing the temperature of the water? How big of a difference in the rate of a chemical reaction can temperature make?

Summary

Areas of Science
Difficulty
 
Time Required
Short (2-5 days)
Prerequisites
None
Material Availability
Readily available
Cost
Very Low (under $20)
Safety
Adult supervision may be needed when working with hot water solutions.
Credits
Andrew Olson, PhD, Science Buddies
Edited by Svenja Lohner, PhD, Science Buddies

Sources

  • Bayer HealthCare, LLC. (2005.). Effect of Temperature on Rate of Reaction. Retrieved July 3, 2013.
  • Swanson, G.C. (n.d.). Chemistry Experiments for the Home: Bubble Rate. Science Department, Daytona Beach Community College.
  • Alka Seltzer® is a registered trademark of Bayer HealthCare LLC.

Objective

To measure the effect of temperature on the rate of a chemical reaction.

Introduction

You may have seen a television commercial for Alka-Seltzer tablets, or heard one of their advertising slogans: "Plop, plop, fizz, fizz, oh what a relief it is!®" When you drop the tablets in water, they make a lot of bubbles, like an extra-fizzy soda, as shown in Figure 1 below. And like a soda, the bubbles are carbon dioxide gas (CO2). However, with Alka-Seltzer, the CO2 is produced by a chemical reaction that occurs when the tablets dissolve in water.

An Alka-Seltzer tablet dissolving and bubbling at the edges
Figure 1. When an Alka-Seltzer tablet comes in contact with water, the tablet makes carbon dioxide gas through a chemical reaction
(Image credit: by Ebarella_R, via Flickr).

Alka-Seltzer is a medical drug that works as a pain reliever and an antacid (antacids help neutralize stomach acidity, such as heartburn). The pain reliever used is aspirin and the antacid used is baking soda (sodium bicarbonate, NaHCO3). To take the tablets, they should be fully dissolved in a glass of water. When sodium bicarbonate dissolves in water, it dissociates (splits apart) into sodium (Na+) and bicarbonate (HCO3-) ions. (An ion is a molecule that has a charge, either positive or negative.) The bicarbonate reacts with hydrogen ions (H+) from citric acid (another ingredient in the tablets) to form carbon dioxide gas and water. In other words, carbon dioxide gas is a product of this reaction. The reaction is described by Equation 1 below:

Equation 1.

So how is temperature related to this bicarbonate reaction? In order for the reaction shown above to occur, the bicarbonate ions have to come into contact with the hydrogen ions. Molecules in a solution are in constant motion, and are constantly colliding with one another. The hydrogen and bicarbonate ions must collide at the right angle and with enough energy for the reaction to occur. The temperature of a solution is a measure of the average motion (kinetic energy) of the molecules in the solution. The higher the temperature, the faster the molecules are moving. What effect do you think temperature will have on the speed, or rate, of the bicarbonate reaction? In this chemistry science project you will find out for yourself by plopping Alka-Seltzer tablets into water at different temperatures, and measuring how long it takes for the chemical reaction to go to completion. In addition, you can record the sound of the Alka-Seltzer fizzle using a smartphone equipped with a sensor app. Do you think it will fizz more loudly in hot or cold water?

Terms and Concepts

Questions

Bibliography

Materials and Equipment

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Experimental Procedure

Note: In this science project, you will investigate how water temperature affects the dissolving time of an Alka-Seltzer tablet. You will use a smartphone equipped with a sensor app to record the fizzing sound of the Alka-Seltzer reaction in water and measure the time it takes for one Alka-Seltzer tablet to react completely in water. The app creates a graph that will not only give you information about the reaction time, but will also allow you to assess how loud each reaction was based on the measured sound intensities. If you do not have a phone, you can observe the reaction and use a stopwatch to time how long it takes for each tablet to dissolve.

If you use the phyphox app to measure the amplitude of sounds, you will need to calibrate the sensor first to get correct decibel readings on your device. The sensor has to be recalibrated between individual recordings. Instructions on how to do the phyphox sound sensor calibration are provided in the video below.
  1. Do your background research and make sure that you are familiar with the terms and concepts in the Background.
  2. In your lab notebook, make a data table like Table 1. You will record your results in this data table.
Condition Temperature
(°C)
Reaction Time
(s)
Optional: Maximum Sound Intensity
(dB)
Trial #1Trial #2 Trial #3 Average Trial #1 Trial #2 Trial #3Average
Hot Tap Water                  
Cold Tap Water                  
Ice Water                  
Table 1. In your lab notebook, make a data table like this one. You will record your results in it.
  1. Prepare a drinking glass so that it is marked at the 200 mL point. You will use the same glass for multiple trials, so it is convenient to mark the desired water level. Note: If your glass fits more than 8 oz, make a mark about 1 inch below the rim.
    1. Add 200 mL (a little less than 1 cup) of water to the drinking glass, or fill it up to about 1 inch below the rim.
    2. Use a piece of masking tape on the outside of the glass to mark the water level, placing the tape with its top edge even with the water level in the glass, as shown in Figure 2.
    3. Note: You do not want to fill the glass completely full because the bicarbonate reaction produces bubbles that could splash out.
A glass jar with a small strip of masking tape on it
Figure 2. Mark your glass on the outside with masking tape to indicate a water level up to about 1 inch below the rim.
  1. You will fill the drinking glass with the same volume of water at three different temperatures: hot tap water, cold tap water, and ice water.
    1. For the hot and cold tap water, run the water until the temperature stabilizes. Fill the glass with water to the level of the masking tape. Be careful when handling the hot water.
    2. For ice water, fill the glass about half full with ice cubes, then add cold tap water to a bit above the level of the masking tape. Stir for a minute or two so that the temperature equilibrates. Once temperature has equilibrated, remove the ice cubes from the water's surface using a spoon or other utensil immediately before adding the Alka-Seltzer tablet. (Pour out any extra water so that the water is up to the level of the masking tape.)
  2. Prepare the drinking glass with one of the three temperatures as described in step 4. Then measure the reaction time for that temperature either by following option 1 (sensor app), described in step 6, or option 2 (stopwatch), described in step 7.

  3. Option 1: Using the Sensor App
    Sensor apps such as phyphox let you record data using sensors that are built into many smartphones, including a microphone that you can use to measure sound. In this project, you can use the app to record the fizzing sound that the Alka-Seltzer tablet makes while it dissolves in water and then use the data to determine the reaction time and maximum sound intensity for each reaction.
    1. Open the sensor app on your phone and select the sound sensor (audio amplitude in phyphox). Remember, that when you are using the phyphox app you will have to calibrate the audio amplitude sensor (sound sensor) before you do any measurements. Do this calibration before you start your investigation, so you get correct sound intensity readings. To calibrate your sound sensor in phyphox, follow the instructions in the sound sensor calibration video. You will have to re-calibrate the audio amplitude sensor (re-set the decibel offset) every time your start a new recording! Once you have calibrated the sensor, make sure you know where the microphone is located on your phone and do a quick test to see if your sound measurement is working. For example, you could record yourself clapping or singing to check if the sensor behaves as expected.
    2. Once you have confirmed that the sensor works and you are familiar with the app, you can start with the experiment. You should do this experiment in a quiet environment. The background reading of your sound meter when there is no noise in the room should be in the range between 20–40 decibels (dB).
    3. Measure the temperature of the water (in Celsius [C]) in the first glass that you prepared, and record it in the data table in your lab notebook. Remove the thermometer from the glass before continuing with the next step.
    4. Put your phone in the waterproof plastic bag and make sure it is sealed well. You don't want it to get wet!
    5. Place the second, same-sized glass, next to the glass filled with water. Lay your phone on top of the second glass so that the microphone (or sound sensor) is located right at the center above the glass filled with water, as shown in Figure 3.
      A smartphone in a plastic bag is placed on the rim of a glass jar so the microphone is above the rim of a second glass jar
      Figure 3. Place your phone on top of the glass filled with water so that the microphone (or sound sensor) is located right at the center above the solution.

    6. Take one whole Alka-Seltzer tablet out of its package and hold it above the glass filled with water. In the phyphox app, start a new recording for your first experiment by pressing the play button.
    7. Once the recording starts, drop the tablet into the water. Note: You have to be very quiet during the experiment. Any sound that you make will be recorded and could affect your data. Try to be as quiet as possible while you are recording your data!
    8. You will immediately see and hear bubbles of CO2 streaming out from the tablet.
    9. The tablet will gradually disintegrate. Observe the graph recorded by the app, and how the sound sensor is responding to the fizzling while all of the solid white material from the tablet disappears.
    10. When the solid material has completely disappeared, and you see on the graph that the sound intensity has reached background levels again or does not change anymore, wait 20 more seconds until all the bubbles have stopped forming, and stop recording your data. Make sure to save your data and label it appropriately such as "hot water," "cold water," or "ice water."
    11. Your data should look something like the graph in Figure 4. Your graph should show an increased sound intensity for as long as the Alka-Seltzer reaction took place. The sound level of the reaction might be louder in the beginning and decrease as the tablet gets smaller. In the graph, every bubble that pops in the solution is represented by a spike.
    12. Measure the time between the beginning of your reaction (when you dropped the tablet, and the sound intensity started to increase) and the end of the reaction (when the sound intensity reached background levels again or does not change significantly anymore). In phyphox, you can use the 'pick data' function to select the respective data points and view their time and decibel values. For example, the reaction in Figure 4 started at 4.1 seconds and ended at about 58.5 seconds.
      Two graphs mark the beginning and end time of an Alka-Seltzer tablet dissolving

      Two graphs measure the decibel levels of an Alka-Seltzer tablet dissolving in water. The minimum decibel level was 20 and the maximum 60.


      Figure 4. This example data from the phyphox app demonstrates how to measure the reaction time of the Alka-Seltzer tablet dissolving. The x-axes of the graphs are time in seconds [s] and the y-axes shows sound intensity in decibels [dB].

    13. Calculate the time difference between these two points. In Figure 4 this would be 58.5 s - 4.1 s, which is 54.4 s. The result is the reaction time for your first trial. Record the reaction time (in seconds [s]) in the data table in your lab notebook.
    14. Tip: Be careful when opening the packets and handling the Alka-Seltzer tablets. The tablets are thin and brittle, so they break easily. If some of the tablets are whole, and some are broken into many pieces, the separate trials will not be a fair test. You should only use whole tablets.

  4. Option 2: Using the stopwatch
    1. After filling the glass to the level of the masking tape, measure the temperature of the water (in Celsius [C]), and record it in the data table in your lab notebook.
    2. Remove the thermometer from the glass before continuing with the next step.
    3. Have your helper get ready with the stop watch, while you get ready with an Alka-Seltzer tablet. Have your helper count one–two–three. On three, the helper starts the stop watch and you drop the tablet into the water.
    4. You will immediately see bubbles of CO2 streaming out from the tablet.
    5. The tablet will gradually disintegrate. Watch for all of the solid white material from the tablet to disappear.
    6. When the solid material has completely disappeared, and the bubbles have stopped forming, say "Stop!" to have your helper stop the stopwatch.
    7. Record the reaction time (in seconds [s]) in the data table in your lab notebook.
    8. Tip: Be careful when opening the packets and handling the Alka-Seltzer tablets. The tablets are thin and brittle, so they break easily. If some of the tablets are whole, and some are broken into many pieces, the separate trials will not be a fair test. You should only use whole tablets.

  5. Repeat step 6 or 7 two more times with the same temperature. If you use the sensor app, make sure your sound sensor is still calibrated and recalibrate it again (re-set the decibel offset) if necessary before each recording.
    1. Repeating an experiment helps ensure that your results are accurate and reproducible.
  6. Repeat steps 5 and 6 or 5 and 7 for each of the other temperatures.
    1. When you are done, you should have done a total of three trials for each of the three temperatures.
  7. Calculate the average reaction time for each of the three water temperatures. Record your results in the data table in your lab notebook.
  8. Make a graph of the average reaction time, in seconds (on the y-axis), vs. water temperature, in degrees Celsius (on the x-axis).
  9. How does reaction time change with temperature? Can you explain why this is?
    1. Hint: If you are having trouble explaining your results, try re-reading the Introduction in the Background.
  10. If you chose to use a sensor app to record your data, look at the graphs for each water temperature again. Write down the maximum sound intensity that you observed during the Alka-Seltzer reaction (not including the initial or end peaks) for each trial. You can get the number in the phyphox app by using the 'pick data' tool to select the timepoint at which the sound intensity is highest. In the example shown in Figure 4, this would be around 15 seconds with a sound intensity of about 60 decibels. Calculate the average for each of the three water temperatures and record your results in the data table in your lab notebook.
  11. Make a graph of the average maximum sound intensity, in decibels (on the y-axis), vs. water temperature, in degree Celsius (on the x-axis).
  12. Which reaction was the loudest? Did you expect these results?
icon scientific method

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Variations

  • More advanced students should also calculate the standard deviation of the reaction times for each temperature.
    • Use the standard deviation to add error bars to your graph.
    • For example, say that the average reaction time for one temperature was 45 seconds, and the standard deviation was 5.2 seconds (these are made-up numbers). You would graph the symbol for the data point at 45 seconds, and then draw short vertical bars above and below the symbol. Each vertical bar would have a length equivalent to 5.2 seconds.
    • Error bars give your audience a measure of the variance in your data.
  • Adult supervision required. Is reaction rate predictable over a larger temperature range? Water remains liquid above 0°C and below 100°C. Repeat the experiment at one or more additional high temperatures to find out. Use Pyrex glass for containing water heated on the stove or in the microwave, and use appropriate care (e.g. wear hot mitts and safety goggles) when handling hot water. A standard candy thermometer should be able to measure the temperatures in this higher range.
  • You could turn the bicarbonate reaction into a home-made lava lamp. To do this, you will want to use a tall jar or empty clear plastic 1-liter or 2-liter bottle, fill it with 2 to 5 centimeters (cm) of water, add 5 drops of food coloring, and then fill it at least three-quarters full with vegetable oil. You could repeat the science project using your home-made lava lamp at a cold and a hot temperature. To do this, you will need to figure out a way to make the prepared bottle hot or cold. (For example, to make it hot you could let it sit in a large bowl of hot water, and to make it cold you could store it in a refrigerator or freezer.) You will also want to use one-quarter of an Alka-Seltzer tablet at a time (instead of a whole tablet). How does the bicarbonate reaction look and function in the home-made lava lamp?
  • In this science project you observed the reaction mixture and watched as the tablets disappeared and formed gas bubbles. For more advanced versions of this experiment, you can build a simple apparatus so that you can measure the volume of the gas produced over time. Because you will be able to collect data at multiple time points, you get information about how the reaction rate changes over time. For more advanced versions of measuring the reaction rate like this, see these Science Buddies projects:
  • Does changing the particle size of the reactants have as big an effect on reaction time as changing the temperature of the water does? For a science project that investigates the effect of particle size on the speed of the reaction, see the Science Buddies project Big Pieces or Small Pieces: Which React Faster?

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General citation information is provided here. Be sure to check the formatting, including capitalization, for the method you are using and update your citation, as needed.

MLA Style

Science Buddies Staff. "Plop, Plop, Fizz Fast: The Effect of Temperature on Reaction Time." Science Buddies, 9 Dec. 2023, https://www.sciencebuddies.org/science-fair-projects/project-ideas/Chem_p027/chemistry/alka-seltzer-effect-of-temperature-on-reaction-time. Accessed 19 Mar. 2024.

APA Style

Science Buddies Staff. (2023, December 9). Plop, Plop, Fizz Fast: The Effect of Temperature on Reaction Time. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/Chem_p027/chemistry/alka-seltzer-effect-of-temperature-on-reaction-time


Last edit date: 2023-12-09
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