physics-air pressure

Air pressure inside the tube prevents water form entering the tube. Once the water level rises above the loop of the tube water pressure becomes greater than the air pressure inside the tube. At this point, water flows into the tube and creates a siphon.

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Magic water bottle
A bottle that gives twenty times more water than you put in. Wow! this will surely solve Melbourne's water shortage problem. Construct the bottle as shown on the right. You will need: -40cm of rubber tubing -2 litre plastic bottle -araldite glue or sealant	Explanation
	Cut a hole in the side of the bottle approximately 5 cm from the bottom. Insert the rubber tubing through the hole and loop it as shown in the picture on the left and in the diagram above.
	Use sealant or Araldite to seal the hole.
	Fill the bottle with water. The level of the water should be just below the loop of the tube as shown on the left. You may wish to paint the outside of the bottle to add more mystery to the exercise. Now add 100ml of water with a small beaker and ask a student to collect the water that comes out from the tube. Ask the student to select a beaker with which to collect the water. Invariably students select a beaker of similar size to the one you used to add water. Keep a larger beaker handy as this will come in very handy, much to the surprise of the students. Click to see a 120 kb video.