A bouncing egg project shows how chemistry can change the outside of an egg without cooking what is inside. When a raw egg sits in vinegar for a day or two, its hard shell slowly disappears and leaves behind a soft, stretchy membrane. This makes the egg feel rubbery and lets it bounce gently from a very low height.
The project matters because it turns an everyday kitchen item into a clear example of acids, reactions, and observation skills.
The eggshell is made mostly of calcium carbonate, and vinegar contains acetic acid. When they touch, the acid reacts with the shell and makes tiny bubbles of carbon dioxide gas. The thin membrane under the shell does not dissolve in the same way, so it stays around the egg and holds the liquid inside.
Students can use this project to learn about chemical reactions, gas formation, membranes, and safe experiment steps.
Key Facts
- Eggshells are made mostly of calcium carbonate, CaCO3.
- Vinegar contains acetic acid, written as CH3COOH.
- Acid + calcium carbonate produces carbon dioxide gas, CO2, which appears as bubbles.
- A simplified reaction is CaCO3 + 2CH3COOH = Ca(CH3COO)2 + H2O + CO2.
- The egg membrane is a thin flexible layer that remains after the shell dissolves.
- Bounce the egg only from a low height, such as 5 cm to 10 cm, because the membrane can break.
Vocabulary
- Acid
- An acid is a substance that can react with certain materials, such as calcium carbonate in an eggshell.
- Calcium carbonate
- Calcium carbonate is the main mineral in an eggshell and has the chemical formula CaCO3.
- Chemical reaction
- A chemical reaction is a process where substances change into new substances with different properties.
- Carbon dioxide
- Carbon dioxide is a gas made during the reaction between vinegar and the eggshell.
- Membrane
- A membrane is the thin, flexible layer under the eggshell that helps hold the egg together after the shell dissolves.
Common Mistakes to Avoid
- Dropping the egg from too high, because the membrane is flexible but not unbreakable and the egg can burst.
- Using a hard-boiled egg instead of a raw egg, because the classic project shows a liquid-filled egg inside a soft membrane.
- Not covering the egg completely with vinegar, because any part above the liquid may keep some shell on it.
- Rushing the soaking time, because the shell usually needs 24 to 48 hours to react enough with the vinegar.
Practice Questions
- 1 An egg is soaked in vinegar for 36 hours. If you check it every 12 hours, how many checks do you make after the egg first goes into the vinegar?
- 2 A student starts with 250 mL of vinegar and adds 75 mL more so the egg is fully covered. What total volume of vinegar is in the cup?
- 3 Explain why bubbles form on the egg while it sits in vinegar, and why the egg can bounce gently after the shell is gone.