Floating+Water


 * Floating Water**



Materials: - Garlic or onion net - Bottle - Rubber bond - Playing card/index card - Water

Procedure:


 * 1) Fill the bottle with almost full of water.
 * 2) Put the index card on top of the lid.
 * 3) While holding the index card in place, turn the bottle over.
 * 4) Wait for 3 seconds then release your hand that's holding the index card in place. The water won't spill.
 * 5) Empty the bottle.
 * 6) Then put the net on the opening of the bottle and secure it with a rubber bond.
 * 7) Fill again the bottle with almost full of water through the screen.
 * 8) Place the index card on top and turn it over.
 * 9) Slowly remove the index card and the water won't spill.

The atmosphere exerts about 14.7 pounds of pressure per square inch of surface at sea level. Since atmosphere is a gas, it does not only pushes downward, but it also pushes upward and sideways. The card remains in place because there is no air inside the bottle and the air pressure outside the bottle is pushing upward harder than the water is pushing downward.
 * Air Pressure (reason for step 4)**

It's because there's also air inside our bodies. The air outside and inside our body balances out that's why it doesn't squash us.
 * How come the Air Pressure doesn't squash me?**



Air pressure can tell us what kind of weather to expect. Barometer is used to measure the air pressure. If a high pressure system is coming, we can expect that the temperature will be cooler and we'll be getting clear skies. And if a low pressure is on its way,we will have a warmer weather, storms and rain.
 * Where do we use air pressure?**

The surface of a liquid behaves as if it has a thin membrane stretched over it.A force called cohesion, which is the attraction of like molecules causes this effect. The reason why the water remains inside the bottle is because the molecules of water joined to form this thin membrane between each opening in the screen.
 * Surface Tension (Reason for step 9)**

Surface tension may be expressed in units of energy (joules) per unit area (square meters). Water has a surface tension of 0.07275 joule per square meter at 20° C (68° F).

- If you ever noticed water drops stuck to windshield, you would know that while large droplets roll down the glass, smallest drops remain stuck.
 * Practical experiences**

- Surface tension lets small insects to walk on water without falling in the water.
 * Role in life sciences**

http://kids.earth.nasa.gov/archive/air_pressure/index.html http://web.mit.edu/nnf/education/wettability/intro.html http://www.stevespanglerscience.com/content/experiment/00000058