Tornado in a Bottle: Create a vortex to talk about extreme weather

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This one is for all the kids (and parents!) that have fun watching the water go down the bathtub drain and create a cool funnel. That, or you’re like me and enjoyed watching tornadoes form while storm chasing in Oklahoma!

This experiment is a way to demonstrate how a vortex, like water draining in the bathtub or a tornado, forms.

Let’s take this experiment for a spin!

How to make the Tornado in a Bottle science experiment

Supplies you will need

For this experiment, you’ll need the following:

Two 2-liter bottles, emptied
Water
Dish soap
Duct tape
Optional: small trinkets that the tornado can swirl around, food coloring

Before you start

The duct tape does not make the experiment completely waterproof. I found that a small amount of water made its way out while we were making a tornado. It may be best to do this experiment over a towel.

Instructions

Here is how to do the Tornado in a Bottle experiment:

Step 1: Add water to one of the bottles

You’ll want to fill the bottle up most of the way, but leave a few inches at the top.

If you want to use food coloring for a visual effect, this would be the time to add it in.

Get your child involved: If you’re using a funnel, see if your child would like to add the water in. Help them pour if they get too rambunctious!

Step 2: Add the dish soap and optional trinkets

The dish soap is for a visual and not totally necessary to see the vortex. It helps the vortex stand out more and can give the illusion of dirt kicking up around your tornado!

This experiment does not need a lot of dish soap to see the effect. In fact, if you add too much, it could result in too many bubbles and the water not flowing as efficiently.

The trinkets are simply for fun and can start the conversation about how powerful tornadoes can be.

Get your child involved: Have your child add a few pumps of dish soap to the bottle and, if you are using trinkets, have them choose the trinkets.

Step 3: Line up the openings of the bottles and tape them

Taking your time with this step is important, as it’s easy to have an accidental spill if things aren’t lined up just right.

I used my fingers to keep the bottle openings aligned as I added more tape. We still ended up with a very minor leak, but doing the experiment on a towel was enough to contain it.

Step 4: Turn the bottle upside-down and initiate the vortex

Once you turn the bottle upside-down, give the top bottle a few turns to initiate the spin for the vortex. After, just let the vortex begin and put on a show!

Get your child involved: Let your child try to initiate the vortex by showing them how to turn the top bottle. They may need help the first couple of times.

The science behind the Tornado in a Bottle earth science experiment

This experiment teaches:

What is a vortex?
How a vortex forms
What is happening inside the vortex

How it works

This experiment puts a scientific explanation behind the vortex that forms in the bathtub for your child.

What is a vortex?

A vortex is a mass of fluid with a whirling or circular motion that tends to form a cavity or vacuum in the center of the circle and to draw toward this cavity or vacuum body subject to its action (defined by Merriam-Webster).

Some examples of vortices are:

Tornadoes, dust devils, hurricanes, waterspouts
Water flowing down the bathtub drain
Galaxies
Stirring your coffee or tea

How a vortex forms

A vortex is formed when a substance circles around an axis point. You can spot them forming when you drain the water from a bathtub, in natural phenomena like tornadoes and hurricanes, and even when you add creamer to your coffee and see little spirals of creamer!

When no other force is acting on a vortex, its rotation (whether it spins clockwise or counterclockwise) is determined by the Coriolis effect.

Here is a really educational and entertaining video that goes further into depth about the rotation direction inside vortices.

In the case of a tornado, the Coriolis effect does not have a direct impact on the rotation of the tornado, since a tornado is not quite large enough for it to play a part in the rotation. Instead, the supercell that the tornado spawns from is affected by the Coriolis effect, so most tornadoes in the northern hemisphere do rotate counterclockwise.

What is happening inside a vortex

This section is going to get a little technical since it’s not easily explained otherwise!

When a vortex forms, it is moving a substance from one location to another location.

In our experiment, we are moving water from one bottle to another bottle. Since the velocity of the water is greater near the bottleneck (where it is transferring to our other bottle), there is a clear velocity difference between the top of our water and the base.

That velocity difference develops a sheer force inside the vortex, forming a vortex.

More earth science experiments to try out with your child

FAQ about the Tornado in a Bottle earth science experiment

How do you make a tornado in a bottle with only one bottle?

If you only have one bottle handy, you can still do this vortex science experiment. Using all of the same supplies (of course with just one bottle instead of two) and the bottle cap to replace the tape, you will initiate the vortex by spinning the bottle around in a giant circle several times. The effect will not last as long, but you will still see a vortex.