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.

Upside down plastic water bottle propelled out of glass jar due to chemical reaction of Alka-Seltzer and water.

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
Water
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 (C₉H₈O₄), sodium bicarbonate (NaHCO₃), and citric acid (C₆H₈O₇).

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:

NaHCO₃ + C₆H₈O₇ → Na₃C₆H₅O₇ + 3H₂O + CO₂

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
Water
1-2 Alka-Seltzer tablets
Wine cork or bottle stopper
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!

Chemical reaction between Alka-Seltzer and water begins inside plastic water bottle.

Plastic water bottle propelled out of the frame of the picture, leaving only a trail of water shooting vertically out of the bottle.

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:

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: