Alka Seltzer Boat Experiment

Alka Seltzer Experiment

The Alka Seltzer Boat experiment is a fun way to explore physics and chemistry with Newton’s Third Law of Motion. There is an equal and opposite reaction for every action! When the Alka Seltzer tablet reacts with water, it produces carbon dioxide gas bubbles. These bubbles push against the water, propelling the boat forward!

Grade Level Recommendation: Kindergarten through 5th Grade

Supplies:

• Bottle cap (or other small, lightweight objects that can float)
• Alka Seltzer tablet (or similar antacid tablet)
• Bowl of water
• Eyedropper or spoon
• Stopwatch (optional for timing your boat!)
• Printable worksheet (see below)

How to Set Up Your Alka Seltzer Boat Experiment:

Prepare the Boat: Place a bottle cap upside down in the bowl of water. Make sure it floats!

Add the Fuel: Drop an Alka Seltzer tablet inside the floating cap.

💡Is there a difference if you break the tablet into pieces first? What happens if you start with just enough water in the bottle cap (still floats) before you add the tablet?

Activate the Reaction: Add a few drops of water to the cap using an eyedropper or spoon.

Watch the Magic Happen! The bubbles formed by the reaction will propel the boat forward across the water.

Optional Challenge: Time how long your boat moves! Experiment with different boat shapes or tablet sizes to see what changes.

The Science Behind It

When the Alka Seltzer tablet touches the water, it creates a chemical reaction between two key ingredients: sodium bicarbonate (baking soda) and citric acid. When these substances dissolve in water, they react to form carbon dioxide gas. This gas forms bubbles that escape from the tablet, pushing the water and creating motion.

According to Newton’s Laws of Motion, the boat moves in the opposite direction when the gas pushes in one direction. It’s like a mini rocket on water (moving horizontally)!

The carbon dioxide gas bubbles reduce the density under the boat, causing it to rise and move. Since carbon dioxide gas is less dense than water, it helps push the boat forward as the bubbles form and escape. The combination of physical forces and a chemical reaction makes this experiment a fun and easy way to explore these concepts!

Extension Activities: Change the variables!

Learn more about variables and apply the scientific method.

• Boat Shape Challenge: Try using different boat shapes (cups, folded paper boats, other bottle caps) and see how they affect the boat’s movement. Do some shapes move faster or farther?
• Tablet Size Experiment: Cut the Alka Seltzer tablets into different sizes. Does using a larger or smaller piece make the boat go faster or slower?
• Speed Race: Set up a race! Try this experiment with multiple boats at the same time and see which one zooms the farthest or the fastest.

Also Try These Fun Boat Projects

• DIY Paddle Boat
• Straw Boat Challenge
• Penny Boat Challenge
• Soap Powered Boat

Related Science Experiments to Explore

• Alka Seltzer Reaction Rate Experiment: Test how temperature affects the reaction rate by dropping Alka Seltzer tablets into different water temperatures.
• Fizzing Rocket Experiment: Want to take propulsion a step further? Launch a fizzy rocket into the air using a similar reaction with a film canister, Alka Seltzer tablet, and water.
• Chemical Reactions with Baking Soda and Vinegar: Similar to the Alka Seltzer experiment, try mixing baking soda and vinegar to observe another chemical reaction that produces gas. What other objects can you propel using this reaction?
• Explore Buoyancy with Different Materials: Investigate what makes objects float or sink by experimenting with different materials in the water. How does shape or material affect whether the object will float or sink?

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