Folding Egg

This activity is part of our Science Lab series. Check out the ANU Science Lab for more experiments! In this activity, you will dissolve an eggshell using household vinegar to extract the inner membrane, exploring acid-base chemical reactions, limiting reagents, and protein structures.

Folding egg experiment materials & ingredients

For this activity:

• 1 raw chicken egg
• White vinegar (acetic acid)
• A glass jar or transparent container
• A straw (for inflating the membrane)

Safety Note: Always wash your hands thoroughly after handling raw eggs or the egg membrane.

How to make a folding egg membrane: Step-by-step instructions

Step 1: Submerge the egg

1. Place a raw egg carefully into your glass jar.
2. Pour white vinegar over the egg until it is completely submerged. You will immediately notice tiny carbon dioxide gas bubbles forming on the eggshell surface.

Step 2: Allow the reaction to complete

1. Leave the egg undisturbed in the vinegar for 24 to 48 hours.
2. Watch as the hard calcium carbonate shell gradually reacts and dissolves, leaving behind the soft, squishy inner egg membrane.

Step 3: Extract and inflate the membrane

1. Gently remove the egg from the jar and wash away any remaining shell residue under cool tap water.
2. Carefully pierce the membrane to empty out the liquid yolk and egg white.
3. Once empty, fold and flatten the delicate membrane.
4. Insert a straw into the small opening and gently blow air inside to watch the folded membrane spring back into its original egg shape!

How a bouncy egg membrane works: The science explained

This classic chemistry and biology activity demonstrates key principles of chemical reactions and cellular structural protection:

• Acid-Base Reaction: Eggshells are made of calcium carbonate (CaCO₃). White vinegar contains acetic acid (CH₃COOH). When combined, they undergo a chemical reaction producing calcium acetate, water, and carbon dioxide gas (CO₂).
• Limiting Reagent: Because there is typically far more calcium carbonate in the eggshell than acetic acid in a single pour of vinegar, acetic acid acts as the limiting reagent. Once the acid is completely used up, the chemical reaction stops.
• Protective Fibrous Proteins: Underneath the hard outer shell, an egg contains two thin inner membranes. These membranes are made of tough, fibrous structural proteins—including collagen, keratin, glycoproteins, and glycosaminoglycans.
• Weak Acid Resistance: Because acetic acid is a weak acid, it breaks down the mineral eggshell without damaging the strong protein bonds in the inner membrane. This leaves behind a flexible, elastic pouch that retains its shape when inflated.

Science fair projects & taking it further: Experimenting with variables

• Test different liquids: Place raw eggs into different acidic household liquids (such as lemon juice, apple cider vinegar, or cola) to compare how quickly they dissolve the shell.
• Osmosis demonstration: After dissolving the shell, soak one membrane in pure tap water and another in corn syrup to observe how water moves across the semi-permeable membrane via osmosis!