You can make a stick figure float in water by drawing it with a dry-erase marker on a smooth, non-porous surface and then gently adding water. The dry-erase ink lifts off the surface and floats due to buoyancy.
This fascinating trick works because of the unique properties of dry-erase marker ink when combined with water.
The Science Behind Floating Stick Figures
The key to making a dry-erase drawing float lies in the composition of the ink and the physics of buoyancy.
- Buoyancy Force: When you add water to the surface with the dry-erase drawing, a buoyant force acts on the ink. According to the reference, "There is a buoyancy Force." This upward force is exerted by the water on the ink.
- Ink Density: Dry-erase marker ink is formulated to be less dense than water. The reference explicitly states, "Because the ink is less dense than the water it wants to float upwards". Objects less dense than the fluid they are in will float.
- Minimal Stickiness: Dry-erase ink is designed not to permanently adhere to smooth surfaces. It has only "slight stickiness," as mentioned in the reference. The buoyancy force of the water is strong enough to "overwhelm" this slight stickiness and lift the drawing off the surface.
- Insolubility: The ink is also largely insoluble in water. This allows it to maintain its shape as it separates from the surface.
Essentially, the water slips underneath the ink, and the upward buoyancy force, driven by the ink's lower density, detaches the drawing from the surface, allowing it to float freely.
Steps to Make Your Stick Figure Float
Here's a simple guide to performing this popular science demonstration:
- Choose Your Surface: Select a smooth, non-porous surface like a ceramic plate, a glass dish, or a mirror. Ensure it is clean and dry.
- Draw Your Figure: Use a fresh dry-erase marker to draw a simple stick figure or another shape on the surface. Keep the lines connected and relatively thick for better results.
- Add Water Gently: Slowly and carefully pour water onto the surface. Avoid pouring directly onto the drawing. Aim the water to the side of the drawing and let it flow across the surface.
- Watch it Float: As the water covers the drawing, the ink should begin to lift off the surface and float on top of the water.
Tips for Success
- Use a relatively new dry-erase marker. Older markers might not work as well.
- Ensure the surface is perfectly clean and dry. Any residue can prevent the ink from lifting.
- Pour the water very slowly and gently. Rapid movement can break up the drawing.
- Warm water can sometimes help the ink lift more easily.
This demonstration is a great way to visually show the concepts of density and buoyancy in action!
