Tornadoes: Making a violent vortex
Purpose/Hypothesis
Tornadoes occur when air masses clash and result in a spinning vortex. The air in the vortex becomes stretched and narrower with time. As the shape of the funnel gradually narrows, it creates an increase in the rotation speed, resulting in a twist similar to that of a spinning skater.
In this experiment you will observe the relationship between the intensity of a vortex and its shape. You will create a vortex using water; a vortex of fluids behaves similar to that of air. A whirlpool and the water in a draining bathtub are examples of a vortex in liquids. The vortex forms when spinning water, or air, is pulled downwards, in this case by gravity. The funnel of water narrows as it is pulled down.
You will fill two bottles with water, create a vortex, and observe the water movement from one bottle to another. You will control the narrowness of the vortex by placing two different size holes between the two bottles. Observing small colored materials placed in the water will provide a way to measure the speed of the water's rotation.
Before you begin, make an educated guess about the outcome of this experiment based on your knowledge of tornadoes and vortexes. This educated guess, or prediction, is your hypothesis. A hypothesis should explain:
- the topic of the experiment
- the variable you will change
- the variable you will measure
- what you expect to happen
A hypothesis should be brief, specific, and measurable. It must be something you can test through further investigation. Your experiment will prove or disprove whether your hypothesis is correct. Here is one possible hypothesis for this experiment: "The speed of the water will increase as the vortex becomes increasingly narrow. "
In this case, the variable you will change is the size of the vortex hole, and the variable you will measure is the speed of the water.
Conducting a control experiment will help you isolate each variable and measure the changes in the dependent variable. Only one variable will change between the control and each of your vortexes. For the control, you will observe the water's speed without narrowing the hole. At the end of the experiment you will compare the intensity of the control with each of the experimental vortexes.
What Are the Variables?
Variables are anything that might affect the results of an experiment. Here are the main variables in this experiment:
- the size of the hole
- the shape of the bottles
- the size of the bottles
- the temperature of the liquid
- the type of liquid
In other words, the variables in this experiment are everything that might affect the vortex. If you change more than one variable at the same time, you will not be able to tell which variable had the most effect on the water's speed.
Level of Difficulty
Easy.
Materials Needed
- two identical 2-liter clear plastic soda bottles
- scissors
- duct tape or electrical tape
- water
- sparkles or any other small visible material that does not dissolve in water, such as oregano
- two washers the same outside diameter as the mouth of the bottles, one with a small center hole and one with a larger center hole
- marking pen
Approximate Budget
$5.
Timetable
30 minutes.
How to Experiment Safely
There are no safety hazards in this experiment.
Step-by-Step Instructions
- Label one bottle "A" and the other "B."
- For your control: Fill Bottle A about two-thirds full of water.
- Sprinkle in some of the sparkles or other visible material.
- Place bottle B upside down on top of bottle A.
- Tape the mouths of the two bottles tightly together with the tape, aligning the openings up exactly. Test for leakage by carefully tilting the bottles.
- Turn the bottles over so that bottle A (with the water in it) is on top of bottle B, and quickly swirl the bottles several times, just like you would spin a hula-hoop. Set the bottles down and observe the water, noting the shape and speed of the swirling water.
- Untape the bottles and tape the washer with the larger hole to the mouth of bottle A. Do not cover the washer hole with tape.
- Again, tape the two bottles tightly together, lining up the mouths exactly. Quickly turn the bottles over and swirl. Note the description of the shape and speed of the vortex.
- Repeat Steps 7 and 8, taping the washer with the smaller hole to bottle A. Note the results.
Summary of Results
Evaluate your results. Was your hypothesis correct? How does the water relate to the actions of a tornado? Compare the results of the two experimental trials with the control experiment. Write a summary of the experiment that explains your results. You may want to include drawings of the shape and speed of each vortex.
Troubleshooter's Guide
Below are problems that may arise during this experiment, some possible causes, and some ways to remedy the problems.
Problem: There was no vortex.
Possible cause: You may not have lined up the washer exactly with the mouths of the bottles, or the tape may have covered some of the circular opening. Repeat the experiment, making sure the opening is clear.
Problem: It was difficult to gauge the speed of the vortex.
Possible cause: Determining the speed of the water is an estimate based on how quickly the sparkles are swirling. You may need to place less sparkles in the bottle. Select the same point on the bottle for every experiment to focus on the swirl.
Change the Variables
To alter this experiment you can change several of the variables, one at a time, and again observe the flow pattern of the water. You can use bottles of different shapes and sizes. You can also try changing the type of liquid you use and the temperature of the liquid. Would the experiment give the same results with a thick liquid substance as opposed to one that has greater flow? Different swirling techniques may also provide interesting results.