Floating and Sinking Grapes

This demonstration uses grapes in soda to show how surface properties affect buoyancy. An unpeeled grape floats to the top of a glass of soda, while a peeled grape sinks. The difference is due to CO₂ bubbles attaching to the grape skin, which changes the grape’s density relative to the liquid.

1. Fill a clear drinking glass with soda (any carbonated drink).
2. Drop one peeled grape and one unpeeled grape into the soda at the same time.
3. Observe that the unpeeled grape rises to the top while the peeled grape sinks to the bottom.
4. Discuss why the two grapes behave differently.

Grapes: Hydrophobic or Hydrophilic? - Culturally Relevant Science:

Grapes - Sinkers and Floaters: Fun Science Experiments - Wilson Middle School Lethbridge Wolverine Productions:

📄 Science Experiments - Concept Research Foundation: https://conceptresearchfoundation.com/2015/11/12/science-experiments/

• Try with different fruits such as raisins, blueberries, or cherries.
• Compare results with soda water (no sugar) vs. sugared soda.
• Repeat the experiment in plain water to see if grapes float without bubbles.

• Avoid spills by performing over a tray or sink.
• Do not eat grapes that have been sitting in soda during the experiment.

• Why does the peeled grape sink to the bottom? (Without skin, it cannot collect CO₂ bubbles, so its density is greater than the soda.)
• Which of the two grapes is lighter in weight? (They weigh about the same, but the unpeeled grape appears lighter because CO₂ bubbles stick to its surface, reducing its effective density.)
• What makes the unpeeled grape float? (Its hydrophobic skin allows bubbles to adhere, making the grape–bubble system less dense than soda.)