A foil boat floats while a foil ball sinks because shape determines how much water is displaced. The foil boat’s open, wide form pushes aside more water, creating a buoyant force that balances its weight. The tightly packed foil ball displaces less water, so the buoyant force is too small to keep it afloat.

1. Tear two equal sheets of aluminum foil.
2. Crumple one sheet tightly into a compact ball.
3. Shape the other sheet into a shallow boat with raised edges.
4. Fill a container with water.
5. Place the foil ball and foil boat gently onto the water surface.
6. Observe: the boat floats while the ball sinks.

#SparkofScience: Buoyancy - The Franklin Institute:

• Hammer the ball into as dense a ball as possible.
• Try different sizes of foil sheets to see how mass and volume affect floating.
• Add coins one by one into the foil boat to test how much weight it can carry before sinking.
• Compare with other materials shaped as boats (plastic wrap, paper).
• Explore how reshaping the foil ball into a flatter disk changes its buoyancy.

• None provided.

• Why does the boat float even though it has the same mass as the ball?
• How does water displacement explain buoyant force?
• What role does density play in floating and sinking?
• How is this principle applied in real boats and ships?