Not your usual experiment, this is a book: “The League of Scientists” is a young adult fiction book by Andy Kaiser (the creator of Digital Bits Science Lab).

Equipment needed:

The League of Scientists is available here: http://www.LeagueOfScientists.com

The Digital Bits Science Lab Experiment:

The League of Scientists is a group of smart kids who love science. They use their knowledge and critical thinking skills to solve seemingly-supernatural mysteries.

One of the components of the book is the mystery aspect, and not just the “main” mystery. In most chapters, there is a puzzle. The solution to the puzzle involves the application of science or critical thinking. The book is intended to give science education (and scientific applications – something you don’t always get from such fiction) while still giving kids a good story and characters.

A simple experiment with a piece of paper shows an interesting aspect of how air pressure works.

Equipment needed:

Paper (Standard letter-size paper will work fine, though heavier paper stock like resume paper or construction paper will work better.)

The Digital Bits Science Lab Experiment:

Fold the piece of paper in half. Then place it on the very edge of a table, so that the paper “tunnel” points off the edge of the table:

Next, stick your face down near the opening to the paper tunnel. Blow a steady stream of air through the tunnel. Try to aim so you’re blowing down by the table surface, in the center of the paper (indicated by the blue arrow).

The paper will bend down towards the table! If the paper is stiff, it’ll bounce back up when you stop blowing. If the paper is flimsy (like regular printer or writing paper), then it’ll flatten down to touch the table surface, and will stay there.

What’s happening here? When you blow air through the paper tunnel, you’re changing the air pressure inside the tunnel. The air pressure between the inside and outside of the tunnel was previously the same. But when you blow air, the air pressure inside the tunnel drops – it’s now lower than the outside air pressure. The outside pressure pushes down on the paper (as indicated by the red arrows), and the paper flattens.

One of the classic fun things to do with a balloon is to “squeak” it. This easy game is the result of some interesting science – air pressure and sound at the molecular level. This is also very similar to the way we use our vocal cords to speak.

Equipment needed:

Balloons

The Digital Bits Science Lab Experiment:

Blow up a balloon. Hold the mouth of the balloon in both hands. Stretch the mouth, pinching your fingers on the balloon while pulling them apart, as in the picture below.

As the air flows out of the balloon, you’ll hear a high-pitched, loud squeaking noise. You can adjust the tension on the balloon mouth, and the pitch and volume of the squeaking will change.

What’s happening here? Why does a balloon squeak when you stretch the mouth?

Stretching the mouth of the balloon makes a very tiny space for the air to flow out of the balloon. The air pressure of the balloon itself forces the air out the mouth, but because of the stretching, that space is limited. The airflow causes the balloon mouth (the stretched part) to vibrate. The vibration makes the noise.

Put your hand on your upper neck – right under your jaw – and hum. You’ll be able to feel a vibration, similar to the vibration at the mouth of the balloon. This is air being forced over your tightly-stretched vocal cords. Remember how tightening or loosening the balloon mouth changed the sound of the squeaking? Hum in a high pitch and feel your neck. Hum in a low pitch, and the vibration will change.

You talk using a similar method to the way the balloon squeaks. But the balloon experiment is a simple demonstration, capable of just a few annoying noises. Your body is a highly-developed machine. You can make noises a lot more impressive than any balloon.

Equipment needed:

Plastic drinking straws

Scissors

The Digital Bits Science Lab Experiment:

What we’re trying to do is to create a simple musical instrument out of a plastic straw. It’s pretty easy. First, cut the top of a straw into what looks like a triangle. (It may help if you squish the straw end first before cutting it – this ensures the cut is the same for the top and bottom of the straw.) When you’re done, one end of your straw should look like this:

Next, blow into the straw. You’ll need to blow pretty hard, and your lips will seal firmly around the straw right at the point where you first made the cut. You may have to move the straw back and forth a bit until you find the right place. The parts of the straw should be flat, and parallel with your tongue – don’t rotate the straw, or the noisemaking will get very difficult or impossible. When you’ve got the right technique, you’ll be rewarded with a buzzing noise coming from the end of the straw.

This is it – we’re making sound! This is the same noise-making concept as reeded musical instruments, like the clarinet and oboe: blowing air over a reed (in this case, our cut straw end) makes that reed vibrate. When it vibrates at the right speed, it makes a noise. A similar technique also allows you to talk. Your vocal cords are just like this straw: you blow air over your vocal cords, and your vocal cords vibrate, and this makes noise come out of your mouth. The difference is that in speaking, your mouth, tongue and many other factors work together. They change various parts of how the air flows and how fast your vocal cords vibrate. This control allows us to form words, sing, and make many other interesting noises.

You can use this concept with our “straw clarinet”, too: cut the straw at the other end (the end you don’t blow into). Shorten it. Make more “straw clarinets”, and cut them to several different lengths. When you blow into these, you’ll find the noise is different from each one. Finally, if you’re really talented, try blowing while changing the tightness of your lips, or varying the amount of air you’re blowing – you’ll find that the noise will change as well.

A leaky bottle can teach how air pressure works, and how strong air pressure is – It can stop water from flowing!

Equipment needed:

One clear, plastic bottle with an airtight top (a two-liter pop bottle with a screw-on cap works great)

A large bowl (something big enough to hold all the water that may be in the plastic bottle)

The Digital Bits Science Lab Experiment:

Punch very small holes (less than a quarter-inch diameter) in the bottom of the plastic bottle. Three holes works well.

Fill the bottle with water. The holes will start draining the water, so you may have to turn the water on full blast to fill, or use one hand to cover the holes.

When the bottle is full, screw the top on tight. If you lift the bottle up, there may be a few drips, but after a few seconds no water should flow out. (If water still glugs out of the bottle at this point, you’ve made the holes too big.)

Unscrew the cap.

The water will start pouring out the holes in the bottom.

If you screw the cap back on before the water drains, the water flow will stop.

What’s happening here? Many things, but one big one is air pressure. With the cap screwed on, the water stays in the bottle. This is because the water needs more air to take the space at the top of the bottle, to replace the space previously filled by the water. Gravity is pulling on the water, and the water tries to flow out, but needs the air to expand and take up more space to do so. The air pressure isn’t changed – the air won’t expand or contract from the very small pull of the water. The air pressure is stronger than the pull of gravity. So the water stays in place.

If the cap is screwed on, there is nothing to replace any space used by the water. So the water doesn’t move. Unscrewing the cap allows air to flow into the bottle, which allows the water to pour out from the bottom, and the air takes up more and more space at the top.

A hovercraft works because of air pressure: it uses a motor to create a cushion of air. The hovercraft floats on this cushion, allowing it to move over land and water.

Build your own balloon-powered mini-hovercraft. It’s a great way to demonstrate the basics of how a hovercraft works. It also demonstrates the concept of air pressure.

Here’s what we’ll build: our balloon-powered hovercraft, all ready for launch:

Equipment needed:

Balloons

Duct tape

A plastic plate with raised edges. The edges themselves should be smooth if possible, not ridged. (Notice that the plate used in the pictures below has ridged edges. It works, but not as well as one with smooth edges.)

A straw

A sharp knife

The Digital Bits Science Lab Experiment:

Cut a straw in half. Stick the straw into the balloon. Duct tape around where the straw meets the balloon mouth. Test for air-tightness: you should be able to inflate the balloon by blowing into the straw. After you inflate the balloon, pinch the straw closed. If you hear the hiss of air, there’s still a leak – add more duct tape or pinch around the seal to close all leaks.

Cut a hole in the middle of the plate. It should be no bigger than the straw.

Turn the plate upside-down. Place the straw/balloon part into the hole in the plate. The straw can extend into the other side of the plate, but shouldn’t be lower than the plate’s edges. (When the plate is sitting upside-down, it should rest evenly on its edges. The straw should NOT be pushing the plate into the air.) Here’s a shot of the bottom of the hovercraft:

Use duct tape to make a seal where the straw enters the plate.

Your final product looks like this:

Here’s detail of the bottom of the hovercraft (which is actually the top side of the plate):

Get another straw. This will be our removable inflater for the balloon.

Crimp the end of the inflater straw. It should look similar to this:

Shove the crimped straw into the balloon-attached straw. If you push firmly, you’ll have a pretty good air seal between the two straws. Blow to inflate the balloon. When you’ve inflated it, you can pinch the straw/balloon part to hold the air in until you’re ready to run the hovercraft.

Here’s a shot of me pinching the hovercraft straw to keep air in the balloon. The inflater straw is still inserted:

Place the hovercraft on a very flat surface, like a table or counter-top, and release the pinch.

The balloon will start pushing air under the plate. The air pressure under the plate will build until the plate floats on a cushion of air. When that happens, the plate will skitter back and forth by itself, until the balloon runs out of air. When the balloon is empty, you can “refill” it again with your inflater straw.

Try different things when you launch the hovercraft: Try spinning it. Try putting it on a hill. Put it in water. Try building hovercrafts with different balloons, and enjoy the results!