Tag Archives: Pressure

Crush Your Cans With Science and Recycle!

September 27th is Crush A Can Day and it’s a day to serve as a reminder that we CAN recycle our aluminum CANS! We love recycling and we’ve got a hot way to do it, with the help of science. 

how to crush a can and recycle

This is an experiment we recommend doing at home! All you need is a can, water, something hot like a stove, and tongs to keep you safe. First, scoop a little water into the can. By heating up the can, water expands into steam. This steam starts taking up all the room in the can, pushing out air.

recycle steam pushes out air

Seal the can with water. This causes two things: 

  1. The water cools down the steam, condensing it back into water. 
  2. Air can’t get back in the can.

seal the can

If air can’t get back in the can, and the steam is now taking up a lot less room because it’s cooler and condensed, you’ve created a can with nothing much in it- a vacuum! Our atmosphere exerts pressure on us all day every day. Up in Idyllwild, around 5000 feet in elevation, our atmosphere pushes about 12 pounds on every square inch of us (AKA 12 PSI). We typically don’t notice this pressure because it’s everywhere and usually evened out. But, not the case with our vacuum-can! And so, the can gets crushed by the pressure of our atmosphere that’s always there. 

crushed with pressure

We hope we’ve inspired you to recycle, and maybe experiment along the way!

Written By: Amanda Williams 

 

Bernoulli’s Principle

Daniel Bernoulli was a Swiss mathematician and physicist in the mid-1700s. He excelled in the fields of statistics and probability, but also was influential in applying mathematics to physical mechanics. Particularly, he is known for his work in fluid dynamics, now known as Bernoulli’s Principle.

bernoulliMost simply, Bernoulli’s Principle is a derivation of the conservation of energy. The sum of all the energies in a steady flow of a fluid (a gas or a liquid) must remain constant. So, if the fluid is forced to move faster, it creates an area of low pressure to compensate.

This principle may seem simple, but it led to the development of two very important machines in the 1900s: the carburetor and the airplane.

The carburetor is the precursor to modern automobile and aircraft engines. Using Bernoulli’s Principle to control the flow of fuel and air, it allowed automobiles and airplanes to control their speed and acceleration with relatively high precision. More efficient methods have since been designed, but without the basis of Bernoulli’s Principle, these machines would never have been developed in the first place.

bernoulli 1Additionally, Bernoulli’s Principle is critical in the design of airplane wings and allowing them to generate lift. The bottom of the wing is flat, while the top part is rounded. As the wing cuts through the air, the gas going over the top has a longer path to take, which requires it to move faster than the air underneath the wing. This creates a low pressure area on the top of the wing. The pressure difference between the top and bottom causes an upwards force to be exerted on the wing, allowing the airplane to fly. While this is not the only source of lift, it is an important factor that allows airplanes to work the way that they do!

Exploring Water

CAUTION: DO NOT ATTEMPT THIS AT HOME

Here is an experiment that even the professionals at AstroCamp will not dare to perform. Water can become superheated in a closed system, like that in a microwave, and become extremely dangerous. Superheated water is liquid water under pressure at temperatures between the usual boiling point, 100 °C, and the critical temperature, 374 °C.

Water

Superheated water can be stable because the liquid water is in equilibrium with the vapor. However, if water becomes superheated due to this equilibrium and a lack of bubbles or impurities, then it will all of a sudden boil if there is a change in the system. This could be a simple as jostling the liquid, introducing something like a spoon, tea bag, or even a tiny piece of dust!

water 1

Smooth containers do not have bubbles of air clinging to their sides. Rough or scratched containers may hold microscopic bubbles in their cracks, becoming nuclei for boiling. These nuclei provide a source for the water to release heat and energy in a safe way. But with a smooth container, when a nuclei is added, the superheated water will explode!

Written by: Mimi Garai

DIY Chemistry: Coca-Cola and Milk

Mixing different liquids together to see what they taste like seems like a part of human nature. But have you ever mixed your favorite drinks together just to see if a chemical reaction will occur? This is an experiment that you can easily DIY, but we do not recommend drinking it. All you need is a bottle of coke and a bit of whole milk.

chemistry 2

Pour the the milk into the full bottle of coke to top it off and then put the cap back on. Mix gently and then keep an eye on it for about an hour.

chemistry

There is a chemical reaction that occurs between the Phosphoric Acid in the coca-cola and the calcium in the milk.

3Ca + 2H3PO4 ///\\\ Ca3(PO4)2 + 3H2

The reaction creates a precipitate, or solid matter, that is more dense than the liquids, therefore sinking to the bottom of the bottle. This precipitate is mostly just milk that has curdled, or become a solid.

chemistry 5

Now that you have separated the liquid and precipitate, try mixing them back together. A simple way to do this is by simply removing the bottle cap. There was a build of pressure in the bottle due to the chemical reactions. Once the bottle cap is removed the change in pressure allows the mixture to recombine. Enjoy!

Written By: Mimi Garai

How Do You Melt Dry Ice?

Dry ice is the solid state of carbon dioxide, the gas we all breathe out, but have you ever seen it in liquid form? When left at room temperature, dry ice doesn’t actually melt; it sublimates, changing directly from a solid to a gas. To understand why, let’s take a look at its phase diagram, a plot of the states of CO2 relative to temperature and pressure.

At standard pressure of one atmosphere, liquid CO2 is unsustainable and any solid carbon dioxide above -109℉, or -78℃, directly converts to a gas. In order for liquid CO2 to exist, the pressure needs to be increased to at least 5.11 atmospheres; which is where our pressure syringe comes in.

Substances tend to condense as pressure increases, changing down in state from gas to liquid or liquid to solid or at least making that state change easier. As the plunger of the pressure syringe drops, the pressure increases to the point where dry ice melts rather than sublimating and CO2 can be held in liquid form.

Just as increasing pressure aids substances in changing down in state, decreasing pressure facilitates changing up in state. At sea level, the boiling point of water is 212 degrees Fahrenheit, but if you live at 5500 feet like those of us at AstroCamp, that boiling point is decreased to 201.5 degrees. This 10.5 degree difference may not seem significant, but that’s the result of a change of less than 0.2 atm. In a vacuum chamber, water will actually boil at room temperature because of the immense drop in pressure.

 

Bernoulli’s Principle Will Leave You Breathless!

What sorcery is this!? Science it turns out! This is a great example of Bernoulli’s Principle! In short, this states that moving air has a lower pressure. Imagine trying to dig a hole in a pool of water: as soon as some of the water gets moved out of the way, the surrounding water rushes in to take its place. Air does the same thing: whenever it moves, the lower pressure draws air in around it!

The cup and straw demonstration shows this nicely, and it’s also a great experiment to try at home! By taking each apparatus and blowing into it, we can see there is a pretty huge difference.

difference

Inside the cup, air is moving quickly. This causes a lower pressure inside the cup than outside, and air that tries to fill up the space suctions the balloon in place. Alternatively, the cup with holes in the sides allows the surrounding air to help out. Very similar to the Bernoulli Bag, nearby air joins in creating a larger column of air that can lift, and even suspend, the balloon.

bernoulli-loop

We know this looks like a trick, because it’s hard to tell from watching that he is exhaling vigorously in both cases. If you don’t believe us, definitely try it yourself!  Of course, it is possible to hold the balloon into the cup by inhaling, but it’s actually more difficult to suck up the balloon from a short distance away! The difference in pressure from blowing fast moving air into the cup is more effective at sucking up the balloon.

While Bernoulli’s Principle can be tricky to understand, it is very important! The fact that fast moving air has a lower pressure is one of the primary ways that airplanes are able to generate lift! The air going over the wing actually goes faster than the air below, which you can see in this very cool shot from a wind tunnel!

wing-wind-tunnel

Credit: Holger Babinsky, University of Cambridge

How do Geysers Erupt to Over 300 Feet?

Note: This experiment shoots boiling water into the air, and should not be attempted at home without proper training and safety equipment!

Geysers are one of nature’s most incredible spectacles. In the most powerful eruptions, water can be shot over 300 feet–or the length of a football field–into the air!

Steam_Phase_eruption_of_Castle_geyser_with_double_rainbow

The Castle Geyser in Yellowstone National Park erupts. Water droplets in the air produce a picturesque rainbow against the blue sky. Photo credit: Brocken Inaglory

But just how do these things work? Geysers require some very specific conditions, which means that they only exist in certain locations. In fact, over half of the world’s geysers live in Yellowstone National Park. To find out why, let’s look at how one of these actually work!

When a geyser erupts, it is going through something known as a hydrothermal explosion, which sounds awesome, if a little complex. Luckily for us, the key to this is something familiar: boiling water. Even more fortunate, most of us have never seen a violent eruption of steam from the stovetop while cooking dinner.

The key to this is something called superheating. Most of us are familiar with the phases of matter. In everyday life, many of the things we see exist solely in a liquid, gaseous, or solid state. However, any material can be in any of these states depending on its heat and pressure. Below is the phase diagram for water. On the left is pressure which gets higher as we move up the diagram, and on the bottom is temperature, which increases as we move right.

Phase-Diagram-Water

Phase diagram for water. In geysers, high pressure can push water’s boiling temperature from 212℉ to almost 500℉, well above the temperature required to burn wood! Image from Pearson Education.

To make a geyser, we need to have superheated water, which simply means water that is boiling at higher than the normal boiling point. You can see on the diagram, increasing the pressure–moving up on the diagram from the normal boiling point–means that water stays in a liquid state until a higher temperature. Bingo! I think we just found out how geysers work!

 

Boiling

There is one more piece of the puzzle: How do we increase the pressure? By capping the boiling vessel, we don’t allow the air out. Capping the flask doesn’t instantly increase the pressure. Instead, as the water boils at the original pressure, liquid water turns into water vapor, which takes up about 1500 times as much space as in ts normal form. To fit in the fixed volume available to it (thanks to the cap) it has to become more tightly packed, which increases the boiling point slightly. This process repeats, causing the pressure to continue to rise and pushing the boiling point higher and higher!

As soon as the flask is open to the air again, we get our hydrothermal explosion: all of the compressed water vapor expands to its normal size flinging the surrounding water into the air, and water above the boiling point follows suit!

Water geyser 2

Levitate a Soda Can

Did you know that Bernoulli’s principle is a statement of conservation of energy? The sum of kinetic and potential energy is constant in every closed system. In fluid dynamics, potential energy is an expression of the pressure within a volume of liquid or gas. When a fluid moves faster (its kinetic energy increases), pressure (potential energy) must decrease to compensate.

uOregonBernoulli

Image credit: University of Oregon

This coupling of behaviors creates fun scientific results! We’ve explained before how to levitate a beach ball with a leaf blower. Today, we’re scaling Bernoulli’s principle down to tabletop size for a super-doable DIY experiment. All you need is an empty soda can and a mug big enough to contain it.

CokeJump

Place the can inside the mug and blow air into the gap between the two containers. Your breath moves faster than the surrounding air, so it creates an area of low pressure around the sides of the can. Stagnant air trapped underneath the can expands to fill the partial vacuum, pushing the can upwards. With a little practice, you’ll be able to jump the can from one mug to another!

Written By: Caela Barry  

Make Your Own Cloud Chamber

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.

StJohnFisherCollege contrail 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. RochesterDecayThis 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!

CloudChamberGif

Written By: Caela Barry

The Magic of Wind & Science!

What sorcery is this!? Science it turns out! This is a great example of Bernoulli’s Principle! In short, this states that moving air has a lower pressure. Imagine trying to dig a hole in a pool of water: as soon as some of the water gets moved out of the way, the surrounding water rushes in to take its place. Air does the same thing!

IMG_9574The cup and straw demonstration shows this nicely, and it’s also a great experiment to try at home! By taking each apparatus and blowing into it, we can see there is a pretty huge difference.

The cup without any holes in the sides actually holds onto the balloon, which is weird, but makes sense. Inside the cup, air is moving quickly. This causes a lower pressure inside the cup than outside, and air that tries to fill up the space suctions the balloon in place. Alternatively, the cup with holes in the sides allows the surrounding air to help out. Very similar to the Bernoulli Bag, nearby air joins in creating a larger column of air that can lift, and even suspend, the balloon.

WizardrySmall2We know this looks like a trick, because it’s hard to tell from watching that he is exhaling vigorously in both cases. If you don’t believe us, definitely try it yourself!

Blowing air through a straw makes a small amount of air move pretty fast. A leaf blower makes a lot of air go really fast! When we add the beach ball, this air rushes around it at high speeds, making a low pressure. Surrounding air is then drawn in from all sides, which holds the ball in place.

 

DiagramWhile it might look like this is just well balanced on a spout of air, this idea falls flat when the angle of the leaf blower is changed. In moving to this orientation, the science stays the same–rushing air still causes the surrounding molecules to rush in and offer support on all sides–despite it looking like magic to the untrained eye!SorcerySmall

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!

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