1. Cut a hole in the top of a twist-off soda bottle cap. I used a Dremel tool to cut mine. The hole needs to pretty much remove the entire cap to give room for the Mentos to drop down into the bottle.
2. Glue the bottle cap into the 1″ side of a 1″ slip to 3/4″ thread PVC adapter. I used gorilla glue, as it foams up and seals it in nicely.
3. Cut an 8″-10″ length of 3/4″ PVC pipe.
4. Next you need to make a trigger mechanism. I used a nail (a 1 1/2 x 16 wire nail from a different project) tied to a piece of string.
5. Drill a hole about 1″ from one end of the PVC pipe in the center of the pipe that is just big enough to allow the nail to slide through easily. Note that some of the soda will come out the holes, so you don’t want them to be too big.
6. To the end with the hole in it, attach a 3/4″ thread to 3/4″ slip PVC adapter.
7. Twist the two adapters together. Why did I use two adapters? I couldn’t find a 1″ slip to 3/4″ slip adapter at my local hardware store.

How to Make It Work:

1. Put the nail through the hole.
2. Add Mentos into the pipe
3. Tighten the unit onto a soda bottle
4. Stand back
5. Pull the string! (make sure to get out of the way of the soda coming out the nail holes)

You may have some questions that relate to the other videos in the series, like:

• Why does the geyser spray out? Check out Episodes 2 and 3 (coming soon)
• What kind of soda works best? Check out Episode 4 (coming soon)
• How many Mentos should I use? Check out Episode 5 (coming soon)
• Does the soda temperature matter? Check out Episode 6 (coming soon)
• What’s the world record for highest soda geyser? Check out Episode 7 (coming soon)

NOTE: A final addition I did after we shot the video was to add a nozzle. This was done by buying a sweeper nozzle for a garden hose, attaching it to a 3/4″ thread to 3/4″ slip PVC adapter, and then putting that onto the other end of the PVC pipe after loading in the Mentos. This greatly increases the height of the spray!

Step one is to build the test apparatus:

1. Attach a hose with two female ends to the end of your garden hose. This is the same kind of hose used for clothes washers and hot water heaters.
2. To the other end of the hose you just attached to the garden hose, hook up a 3/4″ thread-to-slip PVC adapter.
3. Drill a hole into a PVC cap. Mark the size of the hole on the cap so you don’t get them confused. PLEASE make sure to have an adult help you with this part.
4. Put the cap on tight to a 8″-12″ piece of PVC pipe.
5. Repeat 3-4 for each size hole you want to test. I STRONGLY recommend you actually change out the whole cap-and-pipe assembly for each test, as you really want to have the cap on tight. For some of the smaller holes, the pressure can build up to the point that the cap will pop off if not on tight enough.

Now you’re ready to test!

1. Slide a PVC pipe and cap into the PVC adapter attached to the hose.
2. Mount the assembly in place. I used a plastic sawhorse, but a table, chair, or stool will do. The key is to know the exact position from where the water spray begins.
3. Turn on the water.
4. Place a marker at the furthest point the water reaches.
5. Turn off the water.
6. Measure the distance from the test assembly to your marker.
7. Repeat steps 3-6 two more times so you can get an average distance.
8. Remove the pipe and cap.
9. Repeat steps 1-8 above for each additional diameter hole you plan to test

Check your data. Which hole sprayed the furthest?

In my video, we only tested 3 holes. The data we show was our average. But you may find something interesting happens when you get to really small holes – the distance starts to decrease! Why? Well, water experiences friction just like everything else. Friction is a force that opposes motion and makes things slow down, like a baseball player sliding to a stop. In the case of the hose, if the holes get too small, even with all the pressure behind it, there is so little water coming through that friction has a much greater effect and so the water spray doesn’t go as far. You can see this just by going back to the start of this and placing your thumb over the end of a garden hose: there is a “sweet spot” where you get the best distance. If you cover the hose any more or less with your thumb, the spray doesn’t go as far.

1. Get a bamboo skewer (available at most supermarkets) and cut off the pointed end. You can also use a 1/8″ wooden dowel cut to about 12 inches.
2. Duct tape a rubber band to one end of the skewer. I do suggest duct tape, as masking and scotch tape won’t hold as well
3. Cut a drinking straw in half.
4. Thread the other end of the skewer (the one without the rubber band) through one piece of the straw
5. Duct tape the other end of the rubber band to the straw
6. Place the un-taped end of the skewer onto a table, pull the straw down, and then let go. It should go flying!

CAUTION: Do not point it at anyone including yourself when you let go.

What’s Happening?

A stretched rubber band has potential energy. Potential energy means energy that is stored until ready to be transformed into a different type of energy. In this case, the stretched rubber band wants to return to its original shape, so that is what creates the potential energy.

When you let go of the toy, the rubber band snaps back, transforming the potential energy into kinetic energy (energy in motion). That kinetic energy generates the force needed to lift the toy off the table. The more you stretch the rubber band, the more potential energy is available to transform into kinetic energy.

Now some people may say that the potential energy didn’t come from anything, so wasn’t it created? Nope, sorry! That potential energy came from the kinetic energy you used to stretch the rubber band in the first place. And that energy came from the chemical energy stored in the food you ate. And so forth and so on…

Thanks to Eneergcam for his Fun Jumpers Instructable that inspired this video!

1. Flatten one end of a straw, about 1/3″. You can use your fingers or teeth
2. Cut on a diagonal the sides of the flattened portion of the straw to create your “reeds” or the part that will vibrate to create the sound
3. Place your new oboe in your mouth with the reeds parallel to the top and bottom of your mouth.
4. Tighten your lips and blow through the straw. If you don’t hear a sound, adjust your lip tension, slowly loosening and tightening. It takes a little practice to get the hang of it.
5. Once you hear a sound, try shortening your straw length by cutting off pieces. What happens to the sound?
6. Try other kinds of straws that are wider, longer, etc. What happens to the sound?

What’s Happening?

The straw oboe is a tube instrument, which means its length directly correlates to the wavelength of the sound being made. A longer straw has a longer wavelength. Because sound travels at a constant speed, the longer wavelength causes fewer sound waves to pass a point in a second, so it has a lower pitch. But, short tube has a higher wavelength which therefore produces a higher pitch! You can also stop by the Children’s Museum of Houston’s How Does It Work? gallery and explore pitch with strings with Play That Pitch.

1. Place a whole effervescent tablet (like Alka-Seltzer®) into an empty cup.
2. Crush up a second effervescent tablet. I suggest putting it into a folded piece of paper and using a rubber mallet – it makes it much easier to crush and to pour out the crushed matter.
3. Pour the crushed material into a second cup
4. Pour an equal amount of water into each and watch what happens

What’s Happening?

A whole effervescent tablet has a relatively low surface area to volume ration with a great deal of the tablet waiting to react on the inside. But, the higher ratio crushed tablet has exposed a great deal more of the inside to the outside, thereby allowing more of it to react simultaneously.

This same idea is one of the core strengths of nanotechnology. Remember that nanotechnology involves the manipulation of materials at the nanoscale to take advantage of these unusual properties, with the nanoscale involving materials around a billionth of meter. For perspective, your DNA is about 2.5 nanometers (nm) wide and your fingernails grow at the rate of about 1nm per second. Yeah, its really, really, really, really small.

But, being really, really, etc. small has benefits in regards to reaction rate, as they have a VERY high surface area to volume ratio. So, the entire substance can react at a much faster pace. If you want to learn more about nanotechnology, make sure to stop by the Super Small Matter Lab in Matter Factory at the Children’s Museum of Houston or visit http://www.nisenet.org/public.

By the way, thanks to my friends at OMSI and the NISE Network for the experiment that inspired this video!

1. Inflate one 12″ balloon with just air and tie it off.
2. Add water to a second 12″ balloon so it is full when uninflated.
3. Now, blow up the balloon with the water in it and tie it off. Be careful not to let it go unless you want a face full of water.
4. Light a candle (kids, get a parent to help you!)
5. Place the balloon with just air in it over the candle. What happens?
6. Now, place the balloon with the water over the candle. Make sure the water is in the section of the balloon sitting on top of the candle flame.

What’s Happening?

In the balloon with just air, the heat from the candle is pretty much absorbed only by the latex of the balloon, causing it to melt and pop. But, water has a very high heat capacity, which means that the heat energy from the candle that went into the latex was transferred into the water. So, the latex never got hot enough to melt and pop the balloon.

So it is very important for us to sweat, as the water in our sweat absorbs the heat from our skin and our surroundings, helping to keep us cool. In order to sweat, we must be hydrated, which means drinking water at a rate of at least a cup an hour when out in the Houston heat doing anything strenuous (like playing in FlowWorks at the Children’s Museum of Houston). AVOID soft drinks and sugary fruit drinks as both will dehydrate you rather than hydrate you. Sports drinks are okay, but try to get the ones without a lot of sugar.

1. Cool some water down to about 32° F (0°C) using your freezer or extra ice.
2. Measure around a cup of water and find the weight (you’ll see why in a moment).
3. Pour it into a pot on the stove and turn the temperature to high.
4. Time how long it takes to boil.
5. Take the pot off, pour out the water, and let the pot cool down to room temperature.
6. Raise the temperature of some ice to 32° F (0°C) by placing it out at room temperature. Note that some will melt, so you will need to make sure you only use unmelted ice.
7. Measure out equal weight of ice as the water you used earlier. This way, when the ice melts, you have the same amount of water being heated.
8. Pour the ice into the pot on the stove, turn the temperature to high, and time how long it takes for the ice to melt and reach boiling.

What’s Happening?

Even though the ice and water are at the same temperature, ice has bonds that hold its molecules in a crystal pattern. In order to break the bonds and melt the ice, extra heat energy is needed. So, even though the temperature doesn’t rise, heat is absorbed to melt the ice which is why it will take longer for the ice to first melt and then boil.

1. Place about a tablespoon of water inside an empty aluminum can. No need to wrap with foil like we did. We were just covering the brand.
2. Place it on the stove and turn the heat to high.
3. While the can is heating, fill a bowl with cold water – the colder, the better.
4. When you see steam, use tongs to quickly flip the can over upside down into the water. Do NOT touch the can until it has a chance to cool!
5. If it doesn’t crush, you may have either taken too long to flip it, didn’t fully submerge the hole into the water, or pressed the can too far against the bottom. Reheat it and try it again.

What’s Happening?

What we did here was to heat up the air. Heated air expands because warmer air can exert more pressure. Think of it this way – the molecules moving inside the can move faster and faster when heated. All this motion causes them to press harder against each other and the sides of the can. BUT, due to the opening on top, some of the molecules leave the can so the pressure never really rises inside the can. If it were sealed, the pressure woudl rise until  it burst.

When the can is flipped over, we seal the hole. At the same time, the air inside cools, so the molecules aren’t pressing as hard against the sides of the can and the pressure inside drops. But, with the hole sealed, the outside air can’t get inside to equalize the pressure, so the air simply crushes the can (and shoves water up into it). Had the can just been left out to cool, it wouldn’t have crushed.