# DIY Screaming Balloon Experiment

Try out this easy DIY science experiment at home. All you need is a balloon, a penny, and a hex nut. Place the penny or hex nut in the balloon, blow it up and then tie it off. It’s as simple at that! Now give your balloon a good spin and make some observations. Try using many of your senses for this one, but maybe avoid tasting it.

The penny races around and around with little sound, and it takes a really long time to stop spinning. This is due to something called the centripetal force and the conservation of momentum. Centripetal force is the force that makes something continue spinning if it is already in a circular path. It is a force that constantly pulls an object towards the center of its path. Newton’s first law states that an object in motion tends to stay in motion and an object at rest tends to stay at rest unless acted upon by an outside force. In the case of the penny that is constantly spinning in the inside of the balloon, it wants to continue moving. However, if the centripetal force did not exist then the penny would want to travel in a straight line and slam into the inside of the balloon, causing it to come to a crashing halt of motion.

The hex nut also has a centripetal force on it, however the biggest difference between it and the penny is that the hex nut makes a ton of noise. The noise actually comes from the fact the the hex nut has sides. Those sides attribute to more friction which causes vibrations on the balloon. Those vibrations are turned into sound waves, which is the noise that you here. What do you notice as you increase or decrease the rate of rotation of the hex nut? You should be able to notice a definite difference in volume level as well as pitch. If you spin it faster it should get much louder and at a higher pitch. This is also true for other things like vocal chords. The faster that you pass air along them, the higher the pitch will get. What other things can you think of to put inside of your screaming balloon? What differences can you observe?

# DIY Soda Battery

Elementary school students the world over are familiar with potato batteries or lemon batteries, but did you know you can make a battery from soda? With just some wire, two different kinds of metals, and your favorite soda, you can build your own battery!

All you need to do is connect your metal plates to one another with a wire (or connect them to a multimeter as well to measure the battery’s voltage like we did) and place your plates into the soda. Make sure your plates aren’t touching during this experiment because if they touch, the electrons won’t flow through the wire and you won’t see a voltage register on the multimeter.

With our battery, the two metals we’re using are zinc and copper, as zinc is more reactive with the soda than the copper is; leading to a more significant voltage produced by the battery. You could also use the aluminum of the soda can, but you would need to remove the coating from the can with steel wool, as it is designed to prevent the aluminum and soda from reacting with one another. You need two different metals because if both plates are reacting with the soda the same amount, there’s no need for electrons to flow between them and therefor very little voltage produced like you see below when we try making a battery with two copper bars.

To understand how the voltage is generated, let’s take a look at the soda itself for a second. Within the soda is phosphoric acid; the key ingredient to this whole process. That phosphoric acid is breaking up into positive hydrogen ions and negative phosphate ions. Those phosphate ions are attracting the positive nuclei of the zinc and copper atoms, but copper holds its atoms together a little better than the zinc. As a result, a lot of electrons from the now separated zinc atoms are left over in the bar, some of which flow through the wire into the copper bar and establish an equilibrium.

The zinc bar is now fairly close to neutral, but the copper is more negative, so it attracts the positive hydrogen ions which remove some of the excess electrons and combine to form hydrogen gas. That gas floats up through the soda and out of the system. This process is happening in a continuous, rapid cycle so electrons are always flowing from the zinc to the copper.

Over time, the copper bar will start to become slightly positive and will repel some of its positive ions into the soda, some of which will encounter the excess electrons on the zinc bar and form a black coating of copper and copper oxide around the zinc. When that has gone on long enough, the zinc in the soda will be completely coated in copper and the voltage will look like our attempt with two copper plates above, eventually killing the battery.
When we tried with a different soda, Sprite, the voltage produced was roughly the same, but the battery lasted a lot longer because of the stronger acid in the Sprite. Grab your favorite soda and see how much voltage you can generate!

# How it works: Pyrex Glass vs. Vegetable Oil

There isn’t much that comes to mind when we try to compare the similarities of pyrex glass and vegetable oil. No, we are not baking or cooking, we are simply doing an awesome at-home science experiment. It turns out that these two things have something very fundamentally in common: they have the same index of refraction of light!

Light interacts with most things around it. It can travel through things, bounce off of them, and even bend. Reflections are those images that we see in the mirror, it is when light hits a different medium and then bounces off of it. Refraction is when light hits a different medium and instead of completely bouncing off, some light will bounce off of the medium and some of it will bend. To learn more about how we can bend light, click here.

Different mediums can bend light in different ways due to how much they are able to slow it down, referred to as its index of refraction. Water, for instance has an index of refraction of 1.33. Pyrex and vegetable oil both have refractive indexes of 1.47 and air is at about 1.00. If we combine substances with different refractive indexes, we can see some interesting effects.

If you place a small pyrex beaker full of air into a larger pyrex beaker full of vegetable oil you will be able to see the smaller beaker due to the different indexes of refraction of air and pyrex. However, if you let the smaller beaker fill with the oil, it will seemingly disappear because pyrex and vegetable oil have basically the same index of refraction.

# Hiding from Thermal Vision

Thermal cameras operate by looking at objects in a different band of light called infrared, which is the way heat transmits. Ordinarily, you could see a person from behind a wall or other solid object by looking in the infrared, as their heat still passes through that object somewhat, like with the garbage bag (DO NOT TRY THAT AT HOME).

In the case of plexiglass and glass, however, infrared light is not able to pass through, resulting in a blank spot where Jacob’s head and hand used to be. You can even see it with Jacob’s glasses, as they are cooler than most of his face in the infrared.

We actually use this property of plexiglass here at AstroCamp for several solar-powered devices. The inside of our solar ovens are black so they absorb visible light, heating up, and have a plexiglass door covering them so that heat can’t escape. We also use this for a solar water heating system where visible light strikes a black metal tube, which heats up and conducts heat well, then that heat is trapped by a plexiglass covering. Our IR camera is a great source of learning, but it’s also just a lot of fun.

# Anti-Bubbles DIY!

We have all experienced bubbles in our day to day lives, whether its blowing bubbles outside on a summer day, seeing bubbles in the soda that you drink, or blowing through your straw. It’s just a thin sphere of liquid enclosing air or some other type of gas, but what is an anti-bubble?

As you might guess, it is basically just the exact opposite of a regular bubble: a thin sphere of air or other gas that encloses a liquid. Surprisingly, you have probably seen these before without having realized it. Want to make some anti-bubbles? Here is a great DIY experiment that you should definitely try at home. All you will need is some dish soap, water, a pipette, food coloring, two cups and maybe some corn syrup to see even cooler results.

Mix some of the dish soap with water in cup #1 without forming suds. In cup #2, make the same mixture and then add some food coloring. With the pipette, take some of the colored mixture from cup #2 and squeeze it into cup #1 without touching the surface of the liquid in cup #1.  If you do it slowly you should be able to see spheres of liquid resting on top of the surface and then disappearing quickly.  If you squeeze it quickly, the stream of liquid will pull some of the air from above down into the cup, forming an anti-bubble!

To see anti-bubbles in a different way you can use some milk, food coloring, dish soap and a cotton swab. Pour some milk on a plate and drip some food coloring in the middle. With a cotton swab saturated in dish soap, touch the food coloring. You should see an awesome explosion of color from the dish soap repelling from the milk. Now take the cotton swab and gently flick the milk. You might be able to observe some spheres bouncing along the surface. If you did, congratulations, you just made more anti-bubbles!

### WELCOME TO OUR ASTROCAMP BLOG

We would like to thank you for visiting our blog. AstroCamp is a hands-on physical science program with an emphasis on astronomy and space exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and astronomical happenings. This blog has been created by our staff who have at least a Bachelors Degree in Physics or Astronomy, however it is not uncommon for them to have a Masters Degree or PhD. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science, space and astronomy information. Feel free to leave comments, questions, or share our blog with others. Please visit www.astrocampschool.org for additional information. Happy Reading!