Eggs are made up of a semipermeable membrane that allows water and gases to move in and out of the egg shell. When an egg is submerged in vinegar, the acetic acid in the vinegar passes through the egg’s membrane, reacting with the calcium carbonate shell. This reaction breaks down the shell, making it more porous and causing the egg to swell in size as water is absorbed through the weakened membrane.
What happens when you put an egg in vinegar?
Putting an egg in vinegar produces a chemical reaction between the calcium carbonate shell and acetic acid in the vinegar. Here’s a breakdown of the step-by-step process:
- The calcium carbonate shell is made up of calcium, carbon, and oxygen atoms.
- The acetic acid in vinegar dissociates into positively charged hydrogen ions (H+) and negatively charged acetate ions (CH3COO-).
- The hydrogen ions penetrate the eggshell and react with the calcium carbonate.
- The hydrogen ions replace calcium ions, forming calcium acetate, water, and carbon dioxide gas.
- The calcium acetate dissolves into the vinegar, leaving the eggshell full of microscopic pores.
- With the shell’s integrity compromised, vinegar can penetrate to the membrane and make it more porous.
- Water from the vinegar passes through the membrane into the egg, causing it to swell up over time.
This chemical reaction continues slowly over hours or days, until eventually the shell becomes rubbery, bouncy, and greatly expanded in size. The vinegar has dissolved away most of the solid calcium carbonate, leaving just the membrane behind.
What is the chemical reaction?
The chemical reaction between the calcium carbonate eggshell and acetic acid can be summarized by the following equation:
CaCO3 (calcium carbonate) + 2CH3COOH (acetic acid) → Ca(CH3COO)2 (calcium acetate) + H2O (water) + CO2 (carbon dioxide)
The hydrogen ions in the acetic acid swap places with the calcium ions in the calcium carbonate crystal structure. This forms soluble calcium acetate, which dissolves into the vinegar solution. The carbonate is converted into carbon dioxide gas, which bubbles out of the solution. Water is also formed.
What causes the egg to get bigger?
There are two main reasons why the egg swells up in size when put in vinegar:
- Shell Dissolving: The acid reacts with the calcium carbonate shell, dissolving it and making it more porous and fragile. This causes the egg to become flexible and stretchy.
- Water Absorption: With the shell weakened and full of microscopic holes, liquid vinegar can penetrate deeper into the egg. Water from the vinegar passes through the membrane and accumulates inside the egg, making it expand like a balloon.
The combination of the stretchy shell and water absorption causes the dramatic size increase over time. The egg will swell larger and larger the longer it soaks in the vinegar.
Does the raw egg dissolve in the vinegar?
The calcium carbonate shell dissolves, but the raw egg inside does not dissolve in the vinegar. Here’s why:
- The shell acts as a protective barrier, preventing the acid from reaching the insides initially.
- The membrane under the shell remains intact, keeping the egg enclosed as the shell dissolves.
- Protein chains making up the egg white and yolk are too long to break down in weak acetic acid.
- If given enough time, the acidic environment would start to denature and decompose the proteins.
- Normally, the experiment concludes within 2-3 days before protein damage occurs.
So the raw egg stays intact as just the shell weakens and stretches. The insides remain safely contained by the membrane, even as the egg size increases dramatically.
Does the calcium carbonate in the egg’s shell neutralize the vinegar?
No, the calcium carbonate does not neutralize the acetic acid in the vinegar. Here’s why:
- Vinegar contains 3-9% acetic acid, mainly water, and some flavorings.
- An eggshell contains around 2 grams of calcium carbonate.
- The acetic acid in vinegar vastly outweighs the amount of calcium carbonate in the shell.
- The hydrogen ions remain plentiful to continue the reaction.
- Calcium acetate formed is soluble and gets diluted in the vinegar.
- Any effect on acidity is temporary before more acetic acid dissolves in.
So while the released calcium ions do have a slight neutralizing effect, the vinegar solution maintains a low enough pH to keep dissolving the shell. There is no stoichiometric equivalence point reached.
How long does it take for an egg in vinegar to grow?
The time it takes for an egg to grow in vinegar can vary, but the general timeframe is:
- 2-4 hours: Shell starts to soften and become rubbery.
- 8-12 hours: Shell expands slightly in size, vinegar visibly penetrating deeper.
- 24 hours: Egg size has increased noticeably, up to 50% larger.
- 48 hours: Egg is dramatically larger, up to double original size.
- 72+ hours: Egg continues expanding slowly as more liquid penetrates.
Warmer vinegar shortens the reaction time. Massaging the egg can quicken water absorption. Stronger acids (like hydrochloric acid) speed up the shell breakdown. But with standard distilled white vinegar, it takes 1-3 days for the full effect.
Does the type of vinegar matter?
Yes, the type of vinegar affects the reaction rate. Vinegar can be either:
- Distilled white vinegar (5% acetic acid) – This is the common household vinegar used for pickling, cleaning, etc. It will dissolve the shell at a moderate pace.
- White wine vinegar (5-7% acetic acid) – Slightly more acidic than distilled vinegar, so dissolves the shell faster.
- Balsamic vinegar (6-7% acetic acid) – Similar acidity to white wine vinegar, with added flavor.
- Rice vinegar (4-5% acetic acid) – Lower acidity, so slower reaction.
- Apple cider vinegar (5-6% acetic acid) – Slightly more acidic than white distilled vinegar.
For the fastest reaction time, use a vinegar with the highest percentage of acetic acid like white wine or balsamic. Avoid milder vinegars like rice vinegar. Distilled white vinegar gives a reliably consistent result.
Does heating the vinegar speed up the reaction?
Yes, heating the vinegar to an elevated temperature will substantially speed up the reaction rate. There are two reasons why:
- The acetic acid dissociates faster into hydrogen and acetate ions at higher temps.
- The kinetics of the reaction are accelerated with more heat energy.
Heating to 60-70°C (140-158°F) can cut the reaction time down to just 1-2 hours instead of several days. However, this runs the risk of over-softening the egg if left too long. Gentle warming to 40-50°C (104-122°F) in a water bath is ideal for faster but controlled swelling.
Does the concentration of the vinegar solution matter?
Yes, the concentration of acetic acid in the vinegar affects how quickly the eggshell dissolves:
- Higher acetic acid concentrations accelerate the reaction.
- Diluting the vinegar with water slows down the reaction rate.
- Pure glacial acetic acid (99% concentration) dissolves the shell almost instantly.
Using undiluted distilled white vinegar (5% acetic acid) provides a good balance. Diluting to 3% or less acetic acid makes the demonstration too slow. Concentrating to 8% or higher speeds it up dramatically but requires careful safety precautions.
Does the type of egg matter?
The type of egg used in vinegar can have a small effect on reaction rate:
| Egg Variety | Shell Thickness | Reaction Speed |
|---|---|---|
| Chicken | Thinner | Faster reaction |
| Duck | Thicker | Slower reaction |
| Goose | Thickest | Slowest reaction |
Thinner chicken egg shells dissolve quicker than thicker goose egg shells. But the difference is fairly minor, especially given shell thickness variation between individual eggs. Overall, chicken eggs work well and are most convenient.
Conclusion
In summary, an egg grows larger in vinegar due to the acid dissolving the calcium carbonate shell and water penetrating the membrane. Warmer, more concentrated vinegar accelerates the reaction rate. After 1-3 days, the egg will swell up dramatically to 2-3 times its original size. It’s a fun chemical reaction demonstration of acidity’s effect on calcium carbonate.