The naked egg experiment is a safe classroom project that shows how a common kitchen acid can change a familiar object. When a raw egg sits in vinegar for a few days, the hard shell slowly disappears. The egg is called naked because the thin membrane remains while the shell is gone.
This experiment matters because it makes chemical reactions, gases, and cell membranes easy to see.
Key Facts
- Eggshells are mostly calcium carbonate, CaCO3.
- Vinegar contains acetic acid, written as CH3COOH.
- Acid plus calcium carbonate produces carbon dioxide gas, which forms bubbles.
- A simplified reaction is CaCO3 + 2H+ -> Ca2+ + CO2 + H2O.
- The egg membrane does not dissolve like the shell, so it can hold the egg together.
- Osmosis can move water through the egg membrane, changing the egg's size and mass.
Vocabulary
- Acid
- An acid is a substance that can donate hydrogen ions and often reacts with carbonates to make carbon dioxide gas.
- Calcium carbonate
- Calcium carbonate is the main solid material in an eggshell and has the chemical formula CaCO3.
- Carbon dioxide
- Carbon dioxide is a gas with the formula CO2 that appears as bubbles during the reaction between vinegar and eggshell.
- Membrane
- A membrane is a thin flexible layer that can protect the egg and let some substances pass through.
- Osmosis
- Osmosis is the movement of water through a membrane from an area with more water to an area with less water.
Common Mistakes to Avoid
- Using a cooked egg instead of a raw egg is wrong because the inside becomes solid and the membrane behavior is different.
- Not covering the egg completely with vinegar is wrong because only the submerged parts of the shell can react and dissolve evenly.
- Shaking or dropping the egg is wrong because the membrane is soft after the shell dissolves and can easily break.
- Throwing away the vinegar too soon is wrong because the shell usually needs 24 to 72 hours to dissolve fully.
Practice Questions
- 1 An egg has a mass of 58 g before soaking and 64 g after soaking. By how many grams did the egg's mass change?
- 2 A student starts the experiment on Monday at 4:00 p.m. and checks it 60 hours later. What day and time is it when the student checks the egg?
- 3 Explain why bubbles appear on the eggshell in vinegar and why the egg can stay together after the hard shell is gone.