Secondary 12-16 Science Fair Chemistry & Biology

Convert a Egg in a “Ball” that Bounces! 🥚✨

Explore how vinegar dissolves the calcium carbonate shell and leaves a flexible membrane. Measure changes by osmosis and test safe jumps - science you can feel in your hands!

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Subject: Naked and bouncing egg
Duration: 24-48 h (soaking) + 40-60 min (measurements and presentation)
Difficulty: ⭐⭐✩ (intermediate).
Areas: Acid-carbonate reactions, osmosis, elasticity, elasticity

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1) Clear and challenging objectives

General Objective: To obtain a “naked egg” (without shell) that is able to bounce at low altitudes, understanding the phenomena of acid-carbonate reaction and osmosis.
Personal objective: Design and defend a presentation with reliable data (mass, circumference, rebound height) that convinces judges and audience.

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2) Simple and fun theoretical introduction

The bottom line

The shell of the egg is calcium carbonate (CaCO₃). Vinegar contains acetic acid which reacts with CaCO₃, releasing CO₂ (bubbles) and dissolving the peel.
The remaining membrane is semipermeableallows the passage of water. By osmosis, The egg can swell (water enters) or shrink (water leaves) depending on the medium.
The “rebound” to low height It depends on the elasticity of that membrane and the internal fluid. Note! It is not a real ball: there are height limits.

Did you know 🤔

The shell of a chicken egg is made up of millions of microscopic pores - that's why you see bubbles when vinegar works!

Tip: If you change the medium (distilled water vs. syrup), you can demonstrate osmosis by comparing masses and circumferences.

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3) Scientific method: your plan of attack

Observation: An egg with a rigid shell and an inner membrane.
Question: What happens to the egg when immersed in vinegar for 24-48 hours?
Hypothesis: The vinegar will remove the shell, leaving a pliable egg that will bounce low (≤10 cm).
Variables:
- Independent: Soaking time / type of medium (vinegar, distilled water, syrup).
- Dependents: Mass, circumference, safe rebound height.
- Controlled: Egg size, temperature, liquid volume, same vessel.
Experimental Design: Soak eggs in different media and measure daily changes. Test progressive rebound heights of 2 cm by 2 cm.
Data collection: Record in tables (see Annexes).
Analysis: Plot height vs. medium and discuss the role of membrane/osmosis.
Conclusions: Did the data support your hypothesis and what would you improve?

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4) This is what your assembly looks like

ASCII schematic of the assembly

   ┌───────────────────────────┐
   │ FRASCO │
   │ ┌───────────────┐ │
   │ │ │ ││◄─── Membrane (shell dissolves).
   │ │ │ │ (raw) │ │ │ │
   │ └───────────────┘ │
   │ ~~~~~~~~ │
   │ VINEGAR │ (CO₂ bubbles rising).
   │ - - - - - - │
   └───────────────────────────┘

Watch out here! Danger Zone ⚠️

Use goggles y gloves if possible. Vinegar is mildly acidic but may irritate.
The rebound must be to very low height (starts at 2-3 cm). On surface soft (towel/polymer).
Do not press the egg: although flexible, it may break.

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5) Materials with intelligent options

Material	Economic Option	Standard Option	Professional Option
Egg	Local farm	Supermarket (M)	Uniform grade (L/XL)
Vinegar	White 5%	Cleaning 6-8%	Controlled acetic acid
Container	Plastic cup	Glass bottle with lid	Graduate Beaker
Measurement	School rule	Flexible tape	Calibrator / Scale
Protection	Paper towel	Gloves	Safety glasses

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6) Step-by-step guide: your adventure map

Prepare the register (10 min): Create your data table (see Annexes). Tip Pro: Number your eggs (A, B, C).
Initial measurements (10-15 min): Raw egg mass and circumference. Data 0.
Soaking in vinegar (24-48 h): Covers completely. You will see CO₂ bubbles. Change vinegar after 24 h if necessary. Alert: Do not shake the bottle.
Gentle washing (5 min): Remove shell residues under water. Keep membrane intact.
Post-vinegar measurements (10-15 min): Record mass and circumference. Observes elasticity.
Rebound test (10-20 min): On cushioned surface, start at 2-3 cm. Increase by 2 cm at a time until a break or safe limit is seen (<=10 cm).
Osmosis comparisons (optional 1-2 h): Leave another egg in distilled water and another in syrup for 1-2 h and compare changes.
Analysis (20-30 min): Plot rebound height vs. mean; discuss why it changes.

Scientist Alert! If the egg breaks, record the event (height, surface area, time in vinegar) and explain why it failed. Mistakes“ are also data!

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7) Prepare your presentation for the fair

Winning poster

Shocking title: “Can an egg bounce?”
Visual Summary: Process diagram + before/after photos.
Clear Data: Table and graph (height vs. mean; mass/circumference vs. time).
Brief Conclusion: Did you confirm your hypothesis and why?

Phrases to impress judges 🧠

“I controlled variables such as vinegar volume and temperature to isolate effects.”
“The semipermeable membrane accounts for changes by osmosis between different media.”
“I limited the rebound height to reduce risk and obtain comparable data.”

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8) Useful annexes

Data logging template

Day / Time	Medium	Mass (g)	Circumf. (cm)	Rebound height (cm)	Remarks
0	—	—	—	0	Initial measurements
24 h	Vinegar	—	—	—	Dissolved shell?
48 h	Vinegar	—	—	—	Remarkable elasticity
+1 h	Distilled water	—	—	—	Osmosis test
+1 h	Syrup	—	—	—	Comparison

Checklist

▢ Data table prepared
Defined variables (indep./dep./control)
▢ Safety measures (goggles/gloves/soft surface).
▢ Photographs of the process (before, during, after).
▢ Poster-ready graphics.
▢ Conclusion supported by data.

Recommended sources

Consult school chemistry (acid-base reactions, carbonates) and biology (membranes and osmosis) texts to reinforce your theoretical framework.

How to make the Bare Egg and Bouncing Egg: Step by Step Guide