Tornado in a Bottle - Tornado Tube You'll amaze your dinner guests with this cool trick. email to friend
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1. Remove any label from the soda bottle so you have a clear view of the inside. 
2. Fill the soda bottle to the top with water. If you do not have access to a sink nearby or you don't want to move the dinner party to the kitchen, use a large pitcher to fill the bottle.
3. Here's the challenge: How long will it take to empty all of the water in the bottle into the pitcher on the table? Record your prediction on a piece of paper.
4. Without squeezing the sides of the bottle, turn it over and time how long it takes to empty all of the water. You might want to repeat this several times to validate your results. Do the test 3 times and average the results. Keep a table of your results and call this method the Glug-Glug Method. Be sure to use the same amount of water for each of the trials.
5. Fill the bottle to the top with water just as you did before. However, this time swirl the water by moving the bottle in a clockwise or counter-clockwise motion while the water is pouring out. Keep swirling the water until you see the formation of what looks to be a tornado! The water begins to swirl in the shape of a vortex and flows out of the bottle very quickly. 
6. Time this method as you did before, only call it the Vortex Method. Repeat the test several times and average the results. Which method allows the water to exit the bottle more quickly?

The Tornado Tube is a very popular science toy that connects two soda bottles, one filled with water, the other filled with air. Simply swirl the liquid in the bottles and in seconds a twisting, turning, spiraling vortex appears.

Twist of Color - Try adding 2 ounces of colored lamp oil to the water. Lamp oil is available at most department stores where oil lamps are sold. The oil will float on the surface of the water since oil is less dense than water. When the oil and water swirl together, the less dense oil travels down the vortex first and creates a "colored tornado" effect.

How does it work?

If you've ever seen a dust devil on a windy day or watched the water drain from the bathtub, you've seen a vortex. A vortex is a type of motion that causes liquids and gases to travel in spirals around a center line. A vortex is created when a rotating liquid falls through an opening. Gravity is the force that pulls the liquid into the hole and a continuous vortex develops.

Swirling the water in the bottle while pouring it out causes the formation of a vortex. The vortex looks like a tornado in the bottle. The formation of the vortex makes it easier for air to come into the bottle and allows the water to pour out faster. If you look carefully, you will be able to see the hole in the middle of the vortex that allows the air to come up inside the bottle. If you do not swirl the water and just allow it to flow out on its own, then the air and water have to essentially take turns passing through the mouth of the bottle, thus the glug-glug sound.