The hypothesis for the tornado in a bottle experiment should be that: It is likely that the water will transfer faster from the top bottle to the bottom bottle when the water is swirled to create a tornado compared to it just bubbling through.
This is because the tornado means that air can escape the bottom bottle allowing the water to flow through more easily. Creating this vortex also uses gravity to pull the water through to the second bottle.
This can be proven with a stop watch and you can see how much faster you can get the tornado to go! So, you will normally need to work in pairs. Make sure you record all of your findings to either prove or disprove you hypothesis.
After proving this, variants that could be changed in the experiment to see which speeds the water up the most could be; making the bottle sizes bigger, wider or longer, and making the hole between them smaller or bigger.
There are a couple of ways of making this very popular fourth grade science project; the first one involves one bottle, for the other one you will need two bottles, so you can decide which to do depending on how many bottles you have available.
To make a tornado in a bottle using just one bottle (or even a large glass jar), fill it with water until is three quarters full. You can be as imaginative as you like at this stage and add things like food coloring, dish soap, glitter or even toy figures of people, animals and houses so the effect of the tornado can be seen properly.
Once you have put the items that you have decided upon into the bottle or jar, put the lid back on to it, and close it tightly so no water can leak out of it.
Shake the bottle or jar vigorously for a few seconds and then rotate it quickly in a swirling motion. A tornado will appear inside the bottle and you will be able to see it lengthening and contracting.
To make a tornado using two bottles (two liter bottles are a good size to use), you half fill one of the bottles and leave the other one empty. Again, add food colorings and any other bits that you think will add to the effect, glitter is a good addition.
Turn the empty bottle upside down and join the two together by the necks. Keep them in place by using duct tape or electrical tape, making sure that they hold and that no water will be able to leak out from them. Once you are sure the two bottles will hold, turn them over, and quickly swirl them so the water spins. Put them down with the empty one on the bottom and watch the tornado travel into the bottom bottle.
The reason for getting the tornado to work in the bottles is the displacement of air when the water flows through the small area in the neck of the bottles. This rush of water and the displacement of the air produces the tornado.