My PBL Project

1) Gather materials.

2) Using a pair of scissors, cut a circle about the size of the opening of the jar out of the screen.

3) Unscrew the rim of the jar. Replace the tin circle that goes under the rim with the screen circle and screw the rim back on.

4) Using a faucet or a pitcher, fill the mason jar all the way with water. Hold the jar over a sink or a big tub so that in case the water spills, it won't get all over the floor.

5) Hold the jar in your left hand and place the laminated card over the opening of the jar.

*note: If you do not have a laminated card, you can easily make one. Take an empty cereal or cake mix box and cut a square (with scissors) that is big enough to cover the opening of the mason jar. Take a roll of clear scotch tape (the wide-width packaging tape works best) and cut as many strips as you need to cover one side of the square. Tape the strips to the cardboard square. Fold any access over to the other side of the square. Now you have a laminated card! :)

6) Using both hands, slowly turn the jar upside down. Make sure you don't tip the jar! Slowly and carefully slide the laminated card from under the opening of the jar. Removing it slowly will keep the inside of the jar air tight, which will suspend the water.

The water might drip at first, but it should not spill; the water should stay inside the jar.

Yay! You are now witnessing water suspension! :D

7) Now, tip the jar a little. The water should come gushing out. This is because air has been let into the jar, therefore the inside of the jar is no longer air tight and can't hold the water anymore.

8) This demonstration can be performed as many times as you'd like. Once you're done, dry the jar, place the original lid back on it,

dispose of the water from the tub or sink, and put away any non-disposable materials used.

SCIENTIFIC PRINCIPLE

The scientific principle behind my project is adhesion, the properties of air, air pressure and surface tension. Adhesion is when particles of different substances stick together. In this case, the water molecules are attracted to the screen I placed over the opening of the mason jar. So, the water molecules stick to and fill in the gaps of the screen. This creates surface tension. Surface tension is the force that pushes water molecules together and forms a seal. This seal keeps the water from spilling out of the jar.

Air Pressure: The atmosphere exerts about 15 pounds of pressure per square inch of surface at sea level. Because it's a gas, air not only pushes down, but also upwards and sideways. The card remains in place because the pressure of the air molecules pushing up on the card is greater than the weight of the water pushing down. But how does the water stay in the jar when the card is removed? The answer is surface tension.