Watch as I attempt to use air pressure to get an egg in a glass bottle…It doesn’t go too well, but you can try it at home to see if it works!
Air expands when it is heated. If air is heated in a container that prevents expansion, the pressure of the gas increases. When the heat source is removed, the air will contract and decrease in pressure. In a container, this causes the outside air particles to push into the container to equalize the pressure inside and out. Air always flows from a high-pressure system to a low-pressure system (“air flows from high to low”).
In this demonstration, the lit matches heat the air inside the bottle. When air is heated it expands and some of it escapes out the bottle. When the matches go out, the air inside the bottle cools and contracts (takes up less space), thus creating a lower air pressure area inside the bottle than outside. Normally, the higher-pressure air outside the bottle would come rushing in to equalize the lower-pressure air in the bottle. The problem is that the egg is in the way. The air molecules on the outside of the bottle push the egg into the bottle.