Background

  • PK – grade 3 students

At this grade, students know that solids, liquids, and gases have different properties and that the properties of substances can change when the substances are mixed, cooled, or heated. Have you ever used a straw to try to pick up a ping pong ball by breathing in through the straw or shot out a paper wad using a straw? When we breathe in through a straw, we create a suction at the end of the straw that can hold a ping pong ball onto the straw and when we blow out through the straw, we create a pressure at the end of the straw. A similar thing happens in this activity. When the flaming cotton ball is inside the bottle, it heats up and expands the air inside forcing the air out of the bottle. Placing the egg on top of the bottle makes the flame go out and the air inside the bottle cools. The air outside is pushing down on the egg and the inside of the bottle there is a suction. Because there is higher pressure outside the bottle, the egg  is pulled inside the bottle. If we turn the container upside down and heat the container with a hair dryer or flame, the gas inside the container heats up and creates a pressure inside the container that can push the egg out again.

  • Grade 4 – 6 students

At this grade level, kids will know that there are solids, liquids, and gases. Solids have a defined volume and shape, liquids have a defined volume but no defined shape, and gases have neither a defined volume or shape. When the flaming cotton ball is inside the bottle, it heats up and expands the air inside forcing the air out of the bottle. Placing the egg on top of the bottle makes the flame go out and the air inside the bottle cools. The air outside is pushing down on the egg making the air outside and inside unbalanced. This causes the egg to be pulled inside the bottle. To get the egg out of the bottle, there has to be higher pressure inside the bottle to push the egg out. If we turn the container upside down and heat the container with a hair dryer or flame, the gas inside the container heats up and creates a pressure inside the container that can push the egg out again.

  • Middle school students

The pressure outside and inside the bottle is equal. When burning the alcohol on the cotton ball is inside the bottle, it heats up and expands the air inside forcing the air out of the bottle. Placing the egg on top of the bottle creates a seal, extinguishes the flame due to lack of oxygen, and the air inside the bottle cools. The cooler air molecules move slower, create less collision between molecules, and results in a lower air pressure inside the bottle than outside. The air outside is pushing down on the egg making the air outside and inside unbalanced. Due to the higher pressure outside the bottle, the egg is pulled inside the bottle. To get the egg out of the bottle, there has to be higher pressure inside the bottle to push the egg out. This can be done by blocking the mouth of the upside down bottle with the egg and then heating the air inside the bottle in order to make the air molecules move rapidly and make more collision between molecules resulting in a higher pressure.

  • College-level/ scientific description

The pressure outside and inside the bottle is equal. Combustion of the isopropyl alcohol in air creates carbon dioxide and water and, in the process, heats the air inside the bottle. Placing the egg on top of the bottle creates a seal, extinguishes the flame due to lack of oxygen, and the gas inside the bottle cools. The cooler gas molecules move slower, create less collision between molecules, and results in a lower air pressure. The air pressure outside the bottle is higher and is pushing down on the egg making the air outside and inside unbalanced. Due to the higher pressure outside the bottle, the egg  is pulled inside the bottle. To get the egg out of the bottle, there has to be higher pressure inside the bottle to push the egg out. This can be done by the reaction between baking soda and vinegar or by turning the container upside down and heating the container with a hair dryer or flame. In the case of the vinegar and baking soda approach, the pressure of the carbon dioxide gas created by the reaction pushes the egg out of the bottle because of the gas molecules moving more rapidly and colliding with each other increasing the gas pressure inside the bottle. In the case of heating, as gas inside the container heats up the rapid movement of the gas molecules creates a pressure inside the container that can push the egg out again.

Combustion:

alcohol + oxygen —–> carbon dioxide + water

C2H5OH + O2 —-> CO2 + H2O + heat

 

baking soda + vinegar ——-> carbon dioxide + sodium acetate + water

Na(HCO3) + H(C2H3O2)—–> CO2 + Na(C2H3O2) +H2O