Egg in a Bottle Experiment – Two Easy Methods

This entry was posted on by (updated on )
Egg in a Bottle Experiment

The Egg in a Bottle experiment is a classic science project that demonstrates the principles of air pressure in a fun and visually appealing way. Here are two different methods for performing this project, each highlighting how changing temperature in turn changes air pressure and forces a hard-boiled egg into a bottle.

Egg in a Bottle Experiment Materials

  • Glass bottle with a neck slightly narrower than the egg’s diameter
  • Peeled hard-boiled egg
  • Matches or lighter
  • Small piece of paper
  • Hot water
  • Cold water

Finding the right size of bottle is a challenge. Remember there are different sizes of eggs available for sale. A sturdy plastic bottle is an option instead of glass, but sometimes the temperature and pressure change deforms the bottle.

Egg in a Bottle Using a Burning Piece of Paper – Method #1

  1. Preparation: Peel the hard-boiled egg.
  2. Ignite the Paper: Light a small piece of paper using matches or a lighter. Just using a wooden match works too, but a piece of paper typically burns longer and changes the temperature inside the bottle more.
  3. Place the Paper in the Bottle: Quickly drop the burning paper into the bottle.
  4. Position the Egg: Immediately place the peeled egg on the neck of the bottle. If you like, wet the egg with water so it is a bit slippery. Sometimes this helps a larger egg fit through a smaller hole.
  5. Observation: After the flame goes out, the temperature inside the bottle cools and the egg slides into the bottle. Note: the egg does not enter the bottle because fire consumes oxygen! Oxygen merely rearranges into other compounds.

Explanation

When you drop the burning paper into the bottle, it heats the air inside. Heat gives molecules kinetic energy so they move more rapidly and have an increased number of collisions with the wall of the bottle. In other words, heat increases the air pressure inside the bottle. When you place the egg on the bottle, it seals it. Fresh air does not enter the bottle, so the flame consumes the oxygen and then goes out. As the air cools down, it contracts, creating a lower pressure inside the bottle compared to the outside air. The higher external air pressure pushes the egg into the bottle.

Egg in a Bottle Using Hot and Cold Water – Method #2

  1. Heat the Bottle: Place the bottle in hot water, which heats the air inside. (Do not submerge the bottle and fill it with water.)
  2. Position the Egg: After a few minutes, remove the bottle from the hot water and quickly place the peeled egg on the neck of the bottle. (If you like, place the egg on the bottle and then heat it. It makes no difference.)
  3. Cool the Bottle: Immerse the bottom of the bottle in cold water.
  4. Observation: The air inside cools and contracts. The outside air has a higher pressure than the air inside the bottle, pushing the egg through the bottle opening.

Explanation

Heating the bottle with hot water expands the air inside the bottle. Some of it escapes the bottle. The egg seals the bottle. When you place the bottle in cold water, the air inside cools down and contracts, creating a lower pressure inside the bottle. The higher external air pressure pushes the egg into the bottle.

How to Get the Egg Out of the Bottle

There are ways of getting the egg back out of the bottle without breaking it up. Here are three methods:

Method 1: Reversing the Pressure

  1. Tilt the Bottle: Turn the bottle upside down so the egg is at the neck.
  2. Blow Air into the Bottle: Carefully create a seal around the bottle’s mouth with your lips and blow air forcefully into the bottle.
  3. Increase Pressure: The increased air pressure inside the bottle pushes the egg back out through the neck.

Method 2: Lubrication Method

This method works if there is only a small size difference between the egg and the bottle opening.

  1. Add Lubricant: Apply a thin layer of cooking oil or dish soap around the neck of the bottle and the surface of the egg to reduce friction.
  2. Position the Bottle: Turn the bottle upside down so the egg is at the neck.
  3. Gently Shake: Gently shake the bottle. The force of shaking helps slide the egg out. The lubricant makes it easier for the egg to pass through the neck of the bottle.

Method 3: Temperature Change

  1. Position the Egg: Tilt the bottle upside down so the egg is at the neck.
  2. Heat the Bottle: Once the egg is in the bottle neck, carefully change the bottle’s position so you can heat it. Submerge the bottom of the bottle in hot water and heat the air inside. As the air expands, pressure increases and pushes the egg out.

Of course, there is a chance these methods won’t work if the egg is too big. If you really need the egg removed and pressure is not working, insert a stick or wire into the bottle, break the egg, and shake out the pieces.

Relation to the Ideal Gas Law and the Combined Gas Law

The gas law that predicts the behavior of the egg in a bottle experiment is the Combined Gas Law, which is a special case of the Ideal Gas Law.

The equation for the Ideal Gas Law is PV = nRT, where:

  • P is the pressure
  • V is the volume
  • n is the number of moles of gas
  • R is the ideal gas constant
  • T is the temperature

In this experiment, the burning paper or hot water increases the temperature (T) of the air inside the bottle. According to the Ideal Gas Law, if the volume (V) of the bottle remains constant, an increase in temperature results in an increase in pressure (P). When you place the egg on the bottle and the air inside cools, the temperature decreases, leading to a decrease in pressure. The external air pressure (higher P) then pushes the egg into the bottle to equalize the pressure difference.

For the most part, the number of moles of air, volume of air (volume of the jar), and ideal gas constant remain the same throughout the project. This makes using the Combined Gas Law possible. The Combined Gas Law is a rearrangement of the Ideal Gas Law that combines Boyle’s Law, Charles’s Law, and Gay-Lussac’s Law. The Combined Gas Law is given by:

P1V1/T1 = P2V2/T2

where:

  • P is the pressure of the gas
  • V is the volume of the gas
  • T is the temperature of the gas (in Kelvin)
  • Subscripts 1 and 2 refer to the initial and final states of the gas, respectively.

So, if volume remains the same, the equation only balances out when temperature and pressure both increase or both decrease.

Method 1: Using a Burning Piece of Paper

  1. Initial State (before the flame goes out):
    • The burning paper heats the air inside the bottle, increase the temperature (T1).
    • As the temperature increases, the pressure (P1​) inside the bottle also increases.
    • Some of the air escapes the bottle because of the increased pressure. But, it’s not enough to affect the outcome.
  2. Final State (after the flame goes out):
    • The flame consumes the oxygen and the fire goes out, decreasing the temperature (T2​) to decrease.
    • As the temperature decreases, the pressure (P2) inside the bottle decreases. A common misconception is that the pressure decreases because the flame consumes oxygen, forming a partial vacuum. This is incorrect because no oxygen is lost. Instead, combustion forms carbon dioxide and water using carbon and hydrogen from the match or paper. The number and type of atoms inside the bottle remains the same.
    • The volume of the bottle (V) remains constant, so the decrease in pressure creates a partial vacuum inside the bottle.

Result:

  • The lower pressure inside the bottle (P2​) compared to the atmospheric pressure outside causes the higher external pressure to push the egg into the bottle to equalize the pressure difference.

Method 2: Using Hot and Cold Water

  1. Initial State (with the bottle in hot water):
    • Heating the bottle in hot water increases the temperature (T1​) of the air inside the bottle.
    • The increased temperature causes the air to expand, and some air escapes the bottle, slightly increasing the volume temporarily.
  2. Final State (with the bottle in cold water):
    • Placing the bottle in cold water cools the air inside, decreasing the temperature (T2​).
    • As the temperature decreases, the pressure (P2​) inside the bottle decreases.
    • The volume of the bottle (V) is effectively constant after the initial escape of some air, so the decrease in pressure creates a partial vacuum inside the bottle.

Result:

  • The lower pressure inside the bottle (P2​) compared to the atmospheric pressure outside causes the higher external pressure to push the egg into the bottle to equalize the pressure difference.

References

  • Castka, Joseph F.; Metcalfe, H. Clark; Davis, Raymond E.; Williams, John E. (2002). Modern Chemistry. Holt, Rinehart and Winston. ISBN 978-0-03-056537-3.
  • Clausius, R. (1857). “Ueber die Art der Bewegung, welche wir Wärme nennen”. Annalen der Physik und Chemie (in German). 176 (3): 353–79. doi:10.1002/andp.18571760302
  • Raff, Lionel M. (2001) Principles of Physical Chemistry (1st ed.). Pearson College Div. ISBN:  978-0130278050.