Magic Water Cup Science Experiment
What do you think will happen if you turn a cup full of water upside down? You may think all the water will come spilling out! In this fun and easy science experiment, we’re going to show you how to turn a cup full of water upside down and magically keep the water inside. Being able to do this seemingly impossible task may appear magical but we will show you it’s just science.
- A small plastic cup. A 9oz size works well.
- Sink or outside area that can get wet.
- Playing card or index card
- Optional – Little foam balls or something that will float. This adds to the magical illusion of the experiment.
- Fill the cup about three quarters of the way full with water.
- Optional – Add your floating items.
- Place the playing card over the top of the cup making sure the card covers the entire top of the cup.
- Press gently against the card as you rotate the cup upside down. Be sure to do so over a sink in case of any accidental spills.
- After a few moments, remove your hand. The water will appear to magically stay in the cup!
How it Works:
When you place the card on the cup of water, the air pressure inside and outside the cup is the same. As you turn the cup over, a tiny amount of water will escape. This seemingly insignificant amount of water causes the volume of air in the cup to increase. While the volume of air in the cup stays the same, this causes the air pressure inside the cup to decrease. The card will now stay in place even though the cup is upside down because the air pressure outside the cup in now higher than the air pressure inside the cup.
Make This A Science Project:
Try scaling this magic science experiment up. Use larger cups and larger amounts of water. Does the magic water cup experiment continuing working as the size of the experiment increases?