Curious about how air pressure works? Complete this fun and engaging experiment to see how fascinating water can really be as it shows you air pressure in action!
Materials
- 1 Large bowl or container
- Water
- 1 Small clear drinking glass
- Food colouring
- Spoon
How to Do the Air Pressure Experiment
Step 1
Fill the bowl almost to the rim with water.
Step 2
Add a few drops of food colouring to the bowl of water and mix so that it is a constant colour throughout.
Step 3
Submerge your clear glass cup right-side-up into the bowl of water.
Step 4
Turn the glass upside down in the bowl while keeping it fully submerged so that it is now upside down under the water.
Step 5
Make a prediction! What do you think will happen when you first start to lift the glass up from the bowl of colourful water?
Slowly lift the glass up, without letting the top rim of the glass rise past the surface of the water.
Step 6
Make a prediction! What do you think will happen when you lift the glass fully above the surface of the water?
Try lifting the glass fully above the bowl, past the surface of the coloured water.
Where Your Predictions Right?
Did the water do what you thought it would?
When you lifted the glass up slowly, the water should have “magically” stayed inside the glass cup even though it was upside down.
Then, as you lifted the glass, the coloured water should have begun to seep out.
Air Pressure is the Force Behind the "Magic"
Are you wondering why was the water was able to stay in the glass even though it was upside down?
The water is able to stay in the glass (even as it is being lifted up!) because of air pressure pushing down on the water’s surface.
The downward force of the air pressure on the water’s surface causes the water to flow up inside of the cup.
But, as you slowly lift the glass above the surface, it begins to lose air pressure and the water begins to fall out.
Why does the water fall out of the glass as it is lifted above the surface of the water? . . . Once the glass gets lifted out past a certain point (the surface of the water) the force of gravity outweighs the force of the air pressure causing the water to all come out.
Gravity vs. Air Pressure
So why does the water fall out of the glass as it is lifted above the surface of the water?
Once the glass gets lifted out past a certain point (the surface of the water) the force of gravity outweighs the force of the air pressure causing the water to all come out.
What is Gravity?
Gravity is a force of attraction between any two masses. In this case, it would be the water and the air. It is a force that pulls things back to Earth’s surface. For example, a ball that has been thrown into the air returns back to the Earth because the force of gravity pulls it back down.
Next Time, Try This!
Next time you complete this experiment try using two clear glasses at once and see what differences you notice in the water as you pull the glasses out.
