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

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.


Alka-Seltzer® tablets fizz furiously when dropped into water. The moment the tablet starts dissolving, a chemical reaction occurs that releases carbon dioxide gas. Can you make Alka-Seltzer fizz faster or slower by changing the temperature of the water? How big of a difference in the rate of a chemical reaction can temperature make?


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


Andrew Olson, Ph.D., Science Buddies


  • Bayer HealthCare, LLC. (2005.). Experiment 1: The Effects of Temperature on Rate. Retrieved July 3, 2013, from http://alkaseltzer.com/as/student_experiment1.html
  • 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.

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MLA Style

Science Buddies Staff. "Plop, Plop, Fizz Fast: The Effect of Temperature on Reaction Time" Science Buddies. Science Buddies, 9 Oct. 2014. Web. 26 Feb. 2017 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p027.shtml>

APA Style

Science Buddies Staff. (2014, October 9). Plop, Plop, Fizz Fast: The Effect of Temperature on Reaction Time. Retrieved February 26, 2017 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Chem_p027.shtml

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Last edit date: 2014-10-09


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.

Alka-seltzer making carbon dioxide when put in water.

Figure 1. When an Alka-Seltzer tablet is dropped in water, the tablet makes carbon dioxide gas through a chemical reaction.

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 timing how long it takes for the chemical reaction to go to completion.

Terms and Concepts

  • Chemical reaction
  • Alka-Seltzer
  • Baking soda, or sodium bicarbonate
  • Molecule
  • Products
  • Temperature
  • Bicarbonate reaction
  • Reaction rate


  • What is the bicarbonate reaction? What are its products?
  • Keeping in mind that an increase in temperature reflects an increase in the average molecular motion, how do you think increasing temperature will affect the reaction rate?
  • What temperature change do you think would be required to increase, or decrease, the reaction time by a factor of 2?
  • What other factors beside temperature can affect how well a chemical reaction takes place?


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Materials and Equipment

  • Alka-Seltzer tablets (at least 12; if you plan to do additional variations to the project, you will want to get a larger box)
  • Thermometer with a range of at least 0°C to 60°C
    • A suitable thermometer is available from Amazon.com
    • A standard kitchen candy thermometer will also work fine
  • Clear drinking glass or jar (12 ounce [355 mL] or larger)
  • Graduated cylinder, 100 mL. A 100 mL graduated cylinder is available from Amazon.com. Alternatively, measuring cups may be used.
  • Masking tape
  • Something to stir with, such as a spoon or a chopstick
  • Hot and cold tap water
  • Ice
  • Stopwatch or a clock or watch with a second hand
  • A helper
  • Lab notebook
  • Pencil

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Experimental Procedure

In this science project, you will be measuring the time it takes for one Alka-Seltzer tablet to react completely in water. You will investigate how the reaction time changes with water temperature.

  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
Reaction Time
Average Reaction Time
Trial #1 Trial #2 Trial #3 Trial #4
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 250 mL point. You will use the same glass for multiple trials, so it is convenient to mark the desired water level.
    1. Add 250 mL (approximately 1 cup) of water to the drinking glass.
    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.
    3. Note: You do not want to fill the glass completely full because the bicarbonate reaction produces bubbles that could splash out.
  2. 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.)
  3. Prepare the drinking glass with one of the three temperatures as described in step 4. Then measure the reaction time for that temperature.
    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. (It is not a good idea to use the thermometer as a stirring rod. It might break.)
    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. Stir the water gently and steadily. Use the same stirring method and speed for all of your experimental trials. 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.
  4. Repeat step 5 three more times with the same temperature.
    1. Repeating an experiment helps ensure that your results are accurate and reproducible.
  5. Repeat steps 5 to 6 for each of the other temperatures.
    1. When you are done, you should have done a total of four trials for each of the three temperatures.
  6. Calculate the average reaction time for each of the three water temperatures. Record your results in the data table in your lab notebook.
  7. Make a graph of the average reaction time, in seconds (on the y-axis), vs. water temperature, in degrees Celsius (on the x-axis).
  8. 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.

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  • 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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