CAUTION: This experiment uses a hot plate. Please use adult supervision if attempting to recreate.
Bubbles are a great resource for fun and physics. They provide interesting insight for optimization and can even be used as models for atmospheres. Scientists are able to use bubbles as models for the atmosphere because they are very thin compared to the sphere they enclose, just like Earth and it’s atmosphere!
To show this, you can do a very simple experiment, but be sure to have supervision since there is a risk of burn. All you’ll need is a stove top, a metal dish, soap, and a straw. Heat up the metal dish, pour a soap solution on top and blow a bubble into it, using the straw so as to not burn yourself.
You will be able to see vortices form in the film of the bubble. These vortices mimic those of how hurricanes and cyclones form. As the soap film is heated up from the bottom the vortices are formed. The strength of the vortices intensify then die in a uniform way. This is due to convection currents.
Convection currents are the transfer of heat by the mass movement of heated particles into an area of cooler ones. Convection currents on Earth is what causes things like weather and storm patterns. The hotter the planet gets, from geothermal heating and climate change, the more intense weather we will experience.
The same phenomenon can be clearly seen in our bubble hurricanes. The hotter the soap solution becomes, the more intense the vortices will be, but they also die out much more rapidly.
CAUTION: This experiment uses dry ice (-109˚F) and liquid nitrogen (-321˚F). Proper safety equipment should always be used when handling these substances.
Physics tells us that pressure, volume and temperature are all linked when talking about gases. So what does this have to do with solid carbon dioxide (dry ice) and liquid nitrogen? When dry ice is placed into a balloon at room temperature, which is then tied off, it will start to warm up.
Since the ambient air temperature is roughly 65˚F, the air that surrounds the balloon is more than 150 degrees warmer than the dry ice! This hug difference adds energy to the dry ice turning it into gaseous carbon dioxide through the process of sublimation. Sublimation is the phase transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase.
Now that there is a balloon full of carbon dioxide gas we can cool it down with something colder than dry ice. This is where liquid nitrogen comes in. The balloon gets dunked into a bowl full of the -321˚F liquid! Cooling the gas in the balloon down means that it loses energy making the molecules start to clump, making the balloon lose volume. It will turn the carbon dioxide gas back into a solid through the process of deposition. Deposition is basically the opposite of sublimation, turning the gas directly into a solid.
This process of cooling and warming to change the balloon’s volume can be repeated over and over again. Or, with the inflated balloon, dunk it in the bowl of liquid nitrogen, take it out, and before it can expand again, rip it open to see the solid carbon dioxide for yourself!
Can you solve this mystery? There are three balloons, each filled with a different gas. One is nitrogen, one is helium and one is hydrogen. Without knowing which is which, we can conduct a couple different experiments that lets us gain information to determine which gas is in which balloon. But before performing the experiments, we need to know a few things about these gases.
Most of us have seen a Periodic Table of Elements like this one before and while it may seem daunting, it is fairly easy to read. For our purposes, there are only a few things about it that you need to know.
Find what nitrogen, helium, and hydrogen have in common. If you are looking at this periodic table you might notice that these elements are all written in the same color; red. In fact, all of the elements that exist as a gas at room temperature are written in red.
It is important to know that our atmosphere, that is the air we breathe, is made up of about 78% nitrogen gas, 21% oxygen gas, and a trace amount of other gases making up the last 1%.
We need to look at the atomic weight of each of our gases in the balloons and compare them to the atomic weights of the atmospheric gases. The atomic weight of each element can be found in the upper righthand corner of the elements box. For the most part, the periodic table has the elements organized in ascending weight from left to right and top to bottom.
You will need to determine how likely our gases are to react to the oxygen in the atmosphere when introduced to a catalyst, or something that speeds up a reaction. You can find this information by looking at which column each gas is in. Column 1 and 17 are the most reactive. 2 and 16 are second most, 3 and 15 are third, and so on and so forth. But column 18 consists of the Noble Gases, which are extremely stable, and non-reactive.
Now that we have all of that information down, we can use two experiments to isolate which gas is which. First, let’s do a float test. Hydrogen and helium are the two lightest elements, and therefore should float in our atmosphere. Nitrogen is the gas that our atmosphere is mostly made of and therefore should either be neutrally buoyant, or sink in the air. So from experiment #1 we can determine which balloon has nitrogen in it.
All that is left to do is determine which of our floating balloons has hydrogen in it and which has helium. Helium is one of the Noble Gases and should not reacts when in the presence of a catalyst. However, hydrogen is extremely reactive with oxygen, which is why H2O or water is so readily available. So now we need a catalyst. Let’s use fire! It is now extremely easy to tell the difference between helium and hydrogen. When the fire touches the balloon with helium in it, it will pop but not cause a chemical reaction. In contrast, when the fire touches the balloon with hydrogen in it, it will cause an explosion! The explosion is evidence of a chemical reaction occurring. Were you able to solve the mystery of these gases?
WARNING: DO NOT ATTEMPT THIS AT HOME. AstroCamp has a fireproof room and uses the appropriate safety equipment when performing this experiment.
Clouds usually form when water molecules clump together on small particles of dust in the air. These particles are called condensation nuclei. In clean air, they’re hard to come by, so clouds don’t form easily. If conditions are very humid, the air can become supersaturated, or rich with water molecules that would form a cloud if condensation nuclei were available. With nothing to grab on to, though, the molecules stay suspended and invisible… that is, until something disturbs the system.
Image courtesy of St. John Fisher College.
You’ve probably seen this happen before! Jet planes leave contrails, or condensation trails, when they introduce exhaust into supersaturated areas of Earth’s upper atmosphere. This is a common example of foreign particles triggering condensation. Air molecules themselves can also act as condensation nuclei if they’re electrically charged. One way that air molecules become ionized (or charged) is by colliding with radiation from outer space.
Earth receives a constant shower of cosmic rays. Most primary radiation that reaches our atmosphere comes in the form of ultra-high-energy protons, followed in frequency by helium ions and a smattering of other particles. These decay in the upper atmosphere into elementary particles, which go on to ionize thin streaks of the lower atmosphere as they continue hurtling Earthwards. In a supersaturated environment, the newly charged air molecules act as condensation nuclei, leaving a cloudy trail in the wake of the decayed cosmic radiation. The image at left (courtesy of the PARTICLE program at Rochester University) shows primary rays decaying into pions, muons, neutrinos, and gamma rays.
Below, a streak of mist reveals cosmic radiation as it travels through our tabletop cloud chamber. To see cosmic rays for yourself, you’ll need a contained, supersaturated vapor and a bright light source to highlight cloud trails. Science Friday has an excellent step-by-step instruction set that helped us a lot in our DIY design process– check it out!
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!