What's going on?
When you heat up the glass bottle with the boiling water, and then remove the water, the glass stays very hot. This heats up the air inside the bottle. Hot air rises, so a lot of the air inside the bottle rushes out the top. This creates an area of low pressure inside the bottle.
When we cool down the bottle by blowing on it, the air that remained inside the bottle contracts, taking up less space, and reducing the air pressure inside the bottle even further.
Now we have what’s called a pressure differential, where the air pressure outside the bottle is higher than the air pressure inside it. Nature likes to exist in a more even state, and so the easiest solution is to put more air into the bottle until the pressure equalises. Of course, the egg is blocking the only entrance into the bottle, and so the air pushes it into the bottle in order to get access!
Air pressure is the force of molecules of air pushing against things andcan be is a pretty powerful force. It’s responsible for a lot of the weather we see, including some of the wild weather that can cause damage to people and property. Humans also use the way air moves to power machines, and make our lives easier.
Australian Curriculum Links
Year 4 Science: Physical Sciences
Forces can be exerted by one object on another through direct contact or from a distance (ACSSU076)
Other air pressure based science experiments
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