Surface Tension Boat

A tiny boat made from a foam tray (or cardboard) zips across water when a trace of dish soap is applied at its notched stern.

1. Cut a small boat (~5 cm long) from a foam tray or non-corrugated cardboard with a narrow notch at the back.
2. Fill a shallow tray or pie tin with water.
3. Place the boat onto the water.
4. Pour a small amount of dish soap into the notch and watch the boat accelerate forward for a few seconds.
5. Rinse the tray and boat thoroughly with fresh water to remove soap before repeating.

Soap Powered Boat Experiment! - Boundles Brilliance:

Exploring the Physics of a Soap-Powered Boat - JaDropping Science

📄 Build A Soap Powered Model Boat - Science Bob: https://sciencebob.com/build-a-soap-powered-model-boat/

📄 Soap-Powered Boats - Science World: https://www.scienceworld.ca/resource/soap-powered-boats/

• Compare different soaps (dish, hand soap, shampoo) to see which produces the longest run.
• Test water temperature (cold vs. warm) and note effects on speed and distance.
• Try different hull materials (foam, thin plastic, card) and shapes or notch sizes to optimize performance.
• Load the boat with a tiny paper clip to test how added mass affects distance.
• Apply soap asymmetrically (only one notch edge) and observe any turning.

• Do not taste the water or soap; wash hands after the activity.
• Wipe up spills promptly to prevent slipping.

• Why does the boat move only when fresh soap is added? What happens once the water surface is contaminated with soap?
• How does reducing surface tension behind the boat create a net forward force?
• Which design or material gave the best distance, and why?
• How do temperature and added mass change the outcome?