alka seltzer science experiment

Middle School Chemical Engineering For Girls

Great Activities for Middle School Outreach in Chemical Engineering

The Alka Seltzer Reaction

Introduction & motivation.

Chemical reactions are one of the primary focuses for Chemical Engineers. From synthesizing polymers to treating water to creating fertilizers, chemical reactions are important in nearly every aspect of daily life. One job of Chemical Engineers is to classify, understand, and control these reactions to speed them up or slow them down.

Chemical reactions occur when bonds within molecules are broken or formed. There are several things that signify that a chemical reaction took place. These include a change in color, the production of a gas or solid, and of course a change in chemical composition. The starting chemicals before a reaction are called the reactants , and the chemicals that are produced are called the products . The reaction in this activity involves using sodium bicarbonate and citric acid to produce water and carbon dioxide.

Reaction : HCO 3 – (aq) + H + (aq) → H 2 O (l) + CO 2 (g)

The tablets contain sodium bicarbonate (NaHCO 3 ) and citric acid. When the tablet is dissolved in water, bicarbonate (HCO 3 – ) and hydrogen ions (H + ) are formed. Once in solution, the two chemicals can then react according to the reaction listed above. For the reaction to occur, the HCO 3 – and H + must collide at the right angle with the right amount of energy. The chances of this happening are better when the tablet is crushed into more pieces since the molecules have more opportunities to collide and when the temperature is higher, since the molecules are moving faster.

In this activity, students will experiment with the reaction between Alka Seltzer tablets and water in different conditions. By changing temperature and the surface area available for reaction, students will begin to see what factors chemical engineers can control to get the desired result.

This activity introduces the reaction used for the Alka Seltzer Rockets activity, so it is typically performed before building rockets to understand the nature of the reaction before using it.

Chemical Safety:

• Sodium Bicarbonate
• Alka Seltzer tablets
• Large beakers
• Food coloring
• Stopwatches
• Metal spoons
• Thermometers

Before the experiment, ask students to hypothesize what will make the reaction go the fastest and what makes them think that. This can be anything, but try to seek answers with specific regard to the variables being changed in this activity.

The Effect of Temperature on Rate of Reaction

• Partially fill a large beaker with ice cubes. Fill the beaker with water up to the 250 mL mark with cold water and stir the ice water until the temperature equilibrates.
• Measure the temperature of the water and record it in the table.
• Add a tablet and record the time it takes for the tablet to react.
• Repeat 1-2 with room temperature water, then with hot water heated to 70 degrees C using a hot plate.

The Effect of Surface Area on Rate of Reaction

• A whole tablet
• A tablet broken into quarters
• A tablet ground into powder: Place the tablet it a piece of weighing paper (wax or parchment paper work as well) and break it either with your hands or crush it using the back of a metal spoon.
• Add 250 mL of water to a large beaker.
• Measure and record the temperature of the water and make sure it is consistent between trials.
• One student should be ready with a stopwatch and another student should be ready with the whole tablet. The student with the stopwatch should count to three and on three start the stopwatch. At the same time, the other student should drop the tablet into the water.
• Gently stir the water at a consistent speed and pattern.
• As soon as the last of the tablet disappears, yell “Stop!,” stop the stopwatch, and record the time in the table.
• Repeat Steps 2-6 with the quartered tablet and the crushed tablet.

At the end, collect and present all class data on the board. Highlight discrepancies and the general trend.

• Which combination of factors made the reaction go the fastest? The slowest? (Higher surface area and temperature make the reaction go faster. Since the reaction occurs on the surface of the tablet pieces, more access to it will make the reaction go faster because there are more molecules to make bumping together more likely. Higher temperature gives more energy to the molecules, meaning they are more likely to have enough energy for the reaction to continue. The opposite is true for the slowest rate – low surface area and temperature.)
• Why would we want reactions to happen faster or slower? (e.g. we want rusting reactions to be slower to protect metal products, but we want redox reactions that recharge our phone batteries to be fast.)
• Is there a limit to how fast we can make the reaction? Would we want to place a limit if there is not a physical one? (Reactions have maximum rates for a few reasons, like the amount of surface area available to react, if the mixture makes it difficult for molecules to move, etc. If the rate were increased too high, it becomes a safety concern! Sometimes reactions get too fast, too hot, and can’t be slowed down. This is a dangerous runaway reaction , the last thing a chemical engineer wants!)
• Why did any discrepancies come up in the data? What ways could we make our process better to limit those from affecting the class data as a whole? (Discrepancies come up from human error with measuring time, not having precise sizes of tablets, imprecise temperature control across trials, and how hard it is to see a reaction is finished! Let students get creative with suggesting improvements, but a few could include using a grid and knives to chop up tablets or putting the ground tablets through a sieve, using a robot to stir and observe the reaction, and putting the beakers in water baths.)
• We know Alka Seltzer is a medicine to make us feel better. Why might it be designed to fizz? (Fizzing helps the aspirin in the tablet quickly absorb into the bloodstream, making the medicine fast-acting. It might also make it more appetizing to drink!)

Additional Resources

• How Does Alka Seltzer Work?
• VIDEO: Why Does Alka Seltzer Fizz?
• ← Alka Seltzer Rockets
• Separations Activity →

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Alka Seltzer Reaction Rate Experiment

Ready to race with this  Alka Seltzer Reaction Rate Experiment?  In this fun and quick science experiment , you’ll see which Alka-Seltzer tablet dissolves the fastest in water! It’s a fantastic way to explore how temperature affects the rate of chemical reactions . Grab your stopwatch, and let’s get started!

Chemical reactions happen all around us every day, from baking cookies to rusting metal. One important factor that can change how fast a reaction occurs is temperature. In this experiment, you’ll discover how different water temperatures affect the dissolving rate of Alka-Seltzer tablets. This is a great introduction to reaction rates of chemical reactions.

💡 Explore more chemical reactions experiments here.

Grade Level Recommendation:  This experiment is perfect for students in grades 3-5, but younger kids can join with adult supervision.

• Several clear cups or jars
• Water (cold tap water, room temperature tap water, hot tap water)
• Alka-Seltzer tablets
• Thermometer (optional)
• Stopwatch or timer
• Notepad and pencil for observations (printable pages below)

How To Set Up Alka Seltzer Reaction Rate Experiment

Prepare the Water : Gather three clear cups or jars and fill each with water. Ensure each cup has the same amount of water at a different temperature: one with cold water, one with room-temperature water, and one with hot water (🛑 Adult assistance is highly suggested).

Get Ready to Race : Open three Alka-Seltzer tablets and have them ready to drop into the cups simultaneously.

Start the Experiment : Drop a whole tablet into each cup simultaneously and start your timer.

Observe : Watch closely and note how quickly each tablet dissolves at different water temperatures.

Record Your Observations : Write down how long it takes for each tablet to fully dissolve in each cup.

Alka Seltzer Experiment Variables

• Temperature of the water (e.g., cold, room temperature, hot)
• Size of the Alka-Seltzer tablet (whole, half, crushed)
• Amount of water used
• Dependent Variable : This is the variable that you measure, which in this case would be the  reaction rate  or  time it takes for the Alka-Seltzer tablet to completely dissolve .

Science Explanation:

When the Alka-Seltzer tablet dissolves, one of the ingredients, called  sodium bicarbonate , breaks apart into smaller pieces, including  bicarbonate ions . These bicarbonate ions mix with  hydrogen ions  from the  citric acid  in the tablet. 

When they react, they create  carbon dioxide gas  (which makes the bubbles) and  water . The  rate of a chemical reaction  depends on things like water temperature or how the tablet is broken up. The faster the reaction happens, the quicker the bubbles form, which is why the tablet fizzes at different speeds!

Temperature affects the rate of a reaction . When water is heated, its molecules move faster. Faster-moving molecules cause the tablet to break down more quickly, speeding up the chemical reaction. That’s why the tablet dissolves faster in hot water than in cold water. In scientific terms, increasing temperature speeds up the reaction rate, which is a principle that applies to many chemical reactions.

Applying the Scientific Method:

💡This is a fantastic  science fair project  for kids. Kids can explore   variables   and the  scientific method .

• Question : How does the water temperature affect the dissolving rate of Alka-Seltzer tablets?
• Hypothesis : If the water is warmer, then the Alka-Seltzer tablet will dissolve faster.
• Experiment : Use cups of water at different temperatures (cold, room temperature, and hot) and measure the dissolving times of the tablets.
• Observation : Note the time it takes for each tablet to dissolve.
• Conclusion : Compare the times to see which water temperature resulted in the fastest dissolving tablet.

Free Printable Journal Pages

Extension Activities:

• Try Different Temperatures : What happens when using water with ice cubes versus boiling water? Add more temperature variations to explore the relationship further.
• Tablet Size : Break the Alka-Seltzer tablets into smaller pieces. Does size affect the dissolving rate in different temperatures?
• Stirring : Stir the water while the tablet dissolves. How does stirring impact the dissolving rate? Does the effect differ based on water temperature?

💡 Use your Alka Seltzer tablets for a lava lamp experiment , make a rocket and an Alka Seltzer boat experiment.

Related Science Activities

• Temperature and Solubility : Use sugar or salt instead of Alka-Seltzer tablets and observe how temperature affects their dissolving rates in water.
• Fizzing Science : Experiment with vinegar and baking soda to observe how temperature changes the fizzing reaction.
• Pop Rocks Experiment : Drop Pop Rocks into different temperatures of soda and see how quickly they pop, relating it back to temperature and gas production.

Helpful Science Resources

Here are a few resources that will help you introduce science more effectively to your kids or students and feel confident presenting materials. You’ll find helpful free printables throughout.

• Printable Science Project Pack 👇
• Best Science Practices (as it relates to the scientific method)
• Science Vocabulary
• All About Scientists
• Free Science Worksheets
• DIY Science Kits
• Science Tools for Kids
• Scientific Method for Kids
• Citizen Science Guide
• Join us in the Club

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Explore the natural world through science and sustainability

How to Conduct an Alka-Seltzer Rocket Science Experiment

Do you have a plastic bottle and some Alka-Seltzer tablets? Then you have the materials for an Alka-Seltzer rocket science experiment! Read on to learn how to transform a single-use plastic water bottle into a rocket using simple chemistry.

There are a few science experiments that never get old. One of them is launching a homemade rocket high into the air (or onto the roof of my house) and then watching it plummet down to the ground. My kids have had a blast (pun intended) making rockets out of plastic water bottles since they were toddlers. One of the great things about this science activity is that it requires only four household materials:

• Single-use plastic water bottle
• Alka-Seltzer tablet
• Wine cork or bottle stopper

From a sustainability point of view, this is a wonderful way to reuse wine corks and single-use plastic water bottles to learn some basic science principles! One could even argue that, since we are reusing water bottles, they are no longer classified as single-use plastic, which is a win for the environment.

How Does Alka-Seltzer Work?

Alka-Seltzer is a brand of antacid and pain reliever that works by reducing acid in the stomach and relieving pain. It contains three active ingredients: aspirin (C 9 H 8 O 4 ), sodium bicarbonate (NaHCO 3 ), and citric acid (C 6 H 8 O 7 ).

The aspirin in Alka-Seltzer acts as a pain reliever and fever reducer. It works by blocking the production of certain chemicals in the body that cause pain and inflammation.

The sodium bicarbonate in Alka-Seltzer is an antacid that neutralizes stomach acid. This helps to relieve symptoms of heartburn, indigestion, and upset stomach.

The citric acid in Alka-Seltzer reacts with the sodium bicarbonate to produce carbon dioxide gas. This creates a fizzing sensation, which can help to break up and disperse the medication in the stomach, making it more effective.

What Happens When Alka-Seltzer is Put in Water?

When Alka-Seltzer is put in water, it begins to dissolve and react with the water, producing carbon dioxide gas. The reaction between the dissolved sodium bicarbonate and citric acid in the tablet produces sodium citrate, water, and carbon dioxide gas, according to the following chemical equation:

NaHCO 3 + C 6 H 8 O 7 → Na 3 C 6 H 5 O 7 + 3H 2 O + CO 2

The carbon dioxide gas produced during this reaction is responsible for the characteristic fizzing and bubbling that is observed when Alka-Seltzer is added to water.

If you’ve tried making homemade bath bombs with my “ How to Explain the Chemistry of Bath Bombs ” experiment, you may notice a striking similarity: both Alka-Seltzer tablets and my DIY bath bomb recipe rely on two main ingredients – baking soda and citric acid! The chemical reaction between these two substances is responsible for the characteristic fizzing and bubbling of bath bombs, which is precisely the same reaction we see when Alka-Seltzer is mixed with water.

How Can Alka-Seltzer Be Used to Make a Bottle Rocket?

Alka-Seltzer tablets can be used to create a simple chemical reaction that produces carbon dioxide gas, which can be used to propel a small plastic bottle rocket. The carbon dioxide gas produced by the reaction between the Alka-Seltzer and water builds up inside the bottle, creating pressure. Eventually, the pressure becomes strong enough to push the water and the stopper off the top of the bottle, propelling the bottle into the air like a rocket.

What Type of Plastic Bottle Works Best for an Alka-Seltzer Bottle Rocket?

The type of plastic bottle you use to build your Alka-Seltzer-fueled bottle rocket makes a difference. There are 2 key differences between single-use plastic water bottles and single-use plastic soda bottles that will affect the performance of your science project.

Consider the Material of the Plastic Bottle

Single-use plastic water bottles and plastic soda and juice bottles are made from different types of plastic. Water bottles are typically made from polyethylene terephthalate (PET) plastic, which is a lightweight and durable plastic that is also used for food packaging. Soda and juice bottles are often made from a type of plastic called polyethylene (PE), which is also lightweight and durable but has different properties than PET. Due to the acidic nature of soda and juice, the plastic bottle must be resistant to degradation.

Consider the Contents of the Plastic Bottle

Soda bottles are designed to hold carbonated beverages, which means they need to be able to withstand higher pressure than water bottles. As a result, soda bottles are often made with thicker walls and a stronger structure than water bottles.

Plastic Water Bottles > Plastic Soda and Juice Bottles

When choosing which type of plastic bottle to reuse to make an Alka-Seltzer-powered bottle rocket science project, it is best to choose a single-use plastic water bottle. Since we are defying gravity by launching the bottle rocket into the air, we want to use the most lightweight bottle we can find. We are also capitalizing on the bottle not being able to withstand increased pressure, as the forced release of pressure out of the bottle is what will propel our science experiment into the air. 

Learn more about different types of plastic and how they are made here . 

Materials Needed to Conduct the Alka-Seltzer Rocket Science Experiment

Here are the supplies you will need to make a rocket out of a bottle:

• 0.5 L (~16 oz) single-use plastic water bottle 
• 1-2 Alka-Seltzer tablets
• Cup that is approximately the same size as your water bottle
• Safety goggles
• Optional: fins and decorations for your rocket – free, printable fin template here

Instructions to Conduct the Alka-Seltzer Rocket Science Experiment

Once you have gathered your materials, follow these step-by-step procedures to conduct your rocket experiment. This science experiment is ideally suited for an outdoor environment, or an area with a lot of empty vertical space, like a gymnasium. I recommend launching the water bottle rockets outdoors, as you can avoid the water clean-up that will be created!

• Put on safety goggles to protect your eyes.
• Place the cup on a flat surface. This will serve as your launch pad.
• Fill the plastic water bottle about one-third full with water.
• Break an Alka-Seltzer tablet into a few small pieces.
• Drop the Alka-Seltzer pieces into the bottle of water.
• Quickly insert the wine cork into the bottle and place the bottle upside down in the cup.
• Stand back and watch as the rocket takes off!

The carbon dioxide gas produced by the reaction between the Alka-Seltzer and water builds up inside the bottle, creating pressure. Eventually, the pressure becomes strong enough to push the water and the cork off the top of the bottle, propelling the bottle into the air like a rocket.

Note: Be sure to use caution and keep a safe distance when launching the bottle rocket. Make sure that the rocket is aimed away from people, animals, and any fragile objects.

Free Bottle Rocket Fin Templates

Download my free bottle rocket fin templates to transform your plastic water bottle into a flight-worthy vehicle!

FREE Rocket Fin Templates

Alka-Seltzer Rocket Science Lab Videos

Want to see the water bottle rockets in action? Watch as my kids, their friends, and I propel plastic bottles into the air in the following videos:

• Launching Alka-Seltzer-Powered Rockets with Friends
• Backyard Water Bottle Rocket
• Bottle Rocket Bloopers

Encourage Critical Thinking with the Alka-Seltzer Science Lab

Once students have successfully launched the water bottle rockets, ask them the following questions to encourage them to think critically about the science experiment and retest their designs:

• How would the addition of another Alka-Seltzer tablet affect the launch of the rocket?
• How would doubling the water volume affect the launch of the rocket?
• How would grinding the Alka-Seltzer tablet into a powder affect the launch of the rocket?

Investigating these questions will help students understand the connection between the concentration of reactants, the effect weight has on the height of the rocket launch, and how the surface area of the tablet affects the rate of reaction.

More Ways to Reuse Plastic Water Bottles for Science Experiments

Want more science activities that reuse plastic water bottles? Try one of these:

• How to Make a Cartesian Diver: A Boyle’s Law Science Experiment
• Easy Banana Water Landfill Emissions Science Experiment

• 0.5 L (~16 oz) single-use plastic water bottle
• Optional: fins and decorations for your rocket

Instructions

This science experiment is ideally suited for an outdoor environment, or an area with a lot of empty vertical space, like a gymnasium. I recommend launching the water bottle rockets outdoors, as you can avoid the water clean-up that will be created.

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Blow up a balloon with alka seltzer

May 4, 2015 By Emma Vanstone 1 Comment

This is a great, fun way to introduce chemical reactions to children. Even if they’re too young to understand the chemistry behind the reactions themselves, just the idea that a substance can change when another is added is a really useful concept to start to grasp.

We tested alka seltzer and popping candy to see which was the best at blowing up a balloon. You could also try baking soda and vinegar.

What you need

Small bottle

Alka seltzer

Popping candy

Blow up the balloons first and then let the air out. We found this made them blow up a bit faster during the activity.

Fill the small bottles or jars with water, I left a small gap at the top.

Add the alka seltzer to one bottle and popping candy to another before quickly placing the balloons on top.

Watch as the balloons blow up.

Why does this happen?

Popping candy is made by heating the ingredients and then exposing to Carbon Dioxide ( a gas ) at very high pressures before allowing to cool. Tiny bubbles of gas are trapped in the popping candy. When popping candy is added to water it breaks down and releases the carbon dioxide which then fills the available space in the jar and the balloon.

Alka Seltzer contains contain  sodium bicarbonate ( baking soda ) and citric acid. When you drop a tablet into water it forms sodium citrate, water and carbon dioxide which is the bubbles of gas you see. The bicarbonate of soda reacts with the citric acid, this is an acid – base reaction just like we see when we add vinegar to baking soda.

Acid – Base Reactions

 If you place an  acid and a  base  together, they react to neutralise each other, producing a salt. The H(+) cation of the acid  combines with the OH(-) anion of the base to form water.

Extension tasks

What happens if you use warmer water in the jars? Does the balloon blow up faster?

What else could you try?

How about baking soda and vinegar?

Make a film canister rocket

Now you’ve seen just how much gas is released from an alka seltzer, use one to make a film canister rocket . The rocket blasts off because the gas released builds up behind the canister lid, eventually reaching high enough pressure that the tops blows off!

Last Updated on August 26, 2022 by Emma Vanstone

Safety Notice

Science Sparks ( Wild Sparks Enterprises Ltd ) are not liable for the actions of activity of any person who uses the information in this resource or in any of the suggested further resources. Science Sparks assume no liability with regard to injuries or damage to property that may occur as a result of using the information and carrying out the practical activities contained in this resource or in any of the suggested further resources.

These activities are designed to be carried out by children working with a parent, guardian or other appropriate adult. The adult involved is fully responsible for ensuring that the activities are carried out safely.

Reader Interactions

May 05, 2015 at 8:27 pm

My kiddos love these types of experiments. We have the book Naked Eggs by Steve Spangler and the kids always have a blast with his hands-on science experiments.

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