Water is usually pretty predictable. At standard pressures it will boil at 100˚C and freeze at 0˚C. However, under special circumstances it might surprise you. Dihydrogen monoxide can become supercooled, dropping below 0˚C while maintaining the liquid phase of matter.
Acquire distilled or purified water.
Fill an empty bottle with tap water (this is your control).
Place all three bottles in the freezer at the same time
Leave them in for roughly 2 hours (if all of the water was originally at room temperature)
The timing of this will vary with each freezer. After the first hour, check on the bottles periodically to check for signs of freezing.
The bottle filled will freeze before the purified water. At this point you will know that the purified water is below zero, and is ready to be removed from the freezer.
Take it out, give it a hard slam on the table, and watch the H2O turn from liquid to a solid right in front of your eyes!
The liquid will flash freeze into a solid. By hitting it on the table, the water molecules are bumped into alignment in a more crystalline structure, typical in solid ice. This induces a chain reaction that you can follow all the way down the bottle!
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.
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!
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!
You come into contact with nitrogen every day; it makes up 78% of our atmosphere. While it is very common to find nitrogen in its gaseous state, it is much more difficult to find it in its liquid state. That is because liquid nitrogen is very cold. If it gets warmer than -321°F it turns back into a gas.
Liquid nitrogen is made by compressing and expanding regular air. The air is first compressed, which makes the air warm. The compressed air is then cooled to room temperature and then released into a larger container. This transition from high pressure to low pressure results in a cooling of the air based on the ideal gas law, which you can learn morea bout here. It’s the same principle used in refrigerators or air conditioners, but is repeated many more times, allowing the nitrogen to cool off even more and separate from the other gasses in the air. We use liquid nitrogen in many of our experiments, which you can check out here!
One problem is that liquid nitrogen will slowly boil away in storage, so in the month between our fall and spring seasons, any leftover liquid nitrogen will just boil away and be wasted. Instead, we took ours to the pool!
At 86°F, the water is much warmer than the -321°F liquid nitrogen. As a result, the liquid nitrogen begins to turn into an invisible gas, which is not the interesting thing the video shows. The growing white cloud that you see is condensed water vapour from the moist humid air above the warm pool water. As the intensely cold liquid nitrogen is added, the moist, humid air almost immediately condenses, and as the cold spreads out, the cloud follows suit.
Warning: Please note this experiment should not be done with people in the pool. This is not because of the cold (it’s very hard to change the temperature of water), but because of the layer of nitrogen hovering above the pool. The nitrogen pushes the oxygen out of the way. So any swimmers will feel like they’re breathing regular air, but will not be getting vital oxygen. In fact, the room that we dispense liquid nitrogen in has to be large enough and have adequate ventilation to prevent this from happening to people standing nearby.
Have you ever played air hockey? There is something strangely satisfying about how the puck slides effortlessly across the table, before finally coming to rest. This same thing happens naturally as well, and it’s actually some pretty cool science. Lets check out how it works!
When things of different temperatures interact, the warmer object loses its heat to the cooler object. This simultaneously warms up the colder thing, and cools down the warmer thing. This shouldn’t be surprising. It’s the reason that snow melts in your hands and make your hands feel cold. However, when things are of vastly different temperatures, it can get a little strange.
In the video, we are dripping water onto a stovetop that is around 500℉. The water is only about 50℉, but the important part is that the boiling point of water is around 200℉ (technically 212℉ but AstroCamp is at an elevation of about 5600’, which actually lowers the boiling point to about 202℉) which is much lower than the temperature of the stove.
When the drops of water hit the stove, the part that hits first is immediately vaporized because of the difference in temperature. This means that the little droplet of water now has a little barrier of water vapor between itself and the stovetop, which it can float around on. The water droplets seem to bounce and skitter around without boiling away. This is what we call the Leidenfrost Effect. For water, this seems to occur at temperatures of at least 400℉.
It is the same thing that allows a person to pour liquid nitrogen over their hand unharmed (Don’t try this at home, but you can see it below), or dip their hand in water and then dip it in boiling hot lead (DEFINITELY don’t try this at home)!
Humans are approximately 60% dihydrogen monoxide. If this is alarming, it might be helpful to know that this is just water. While water is certainly something quite familiar, it has a lot of properties that are very important and they all come from its famous chemical formula, H2O. Let’s take a look and try to understand a few.
Water molecules−which you can see an illustration of on the right−are made up of one Oxygen atom and two Hydrogen atoms. When atoms are bonded together, they do so because of electric charges. In this case, each hydrogen atom has one electron that it shares with the oxygen atom. Electrons carry a negative charge, and are held closer to the oxygen atom. This gives the oxygen atom a negative charge while leaving the hydrogen atom slightly positive. As you have almost certainly hear, opposites attract. These opposite charges pull on one another which keeps the water molecule together amidst a microscopic sea of atoms.
Due to this and the shape of the water molecule, each has a negative part where the oxygen is and a positive part where the hydrogen is. Scientists call molecules like this polar, and it is this polarity that gives rise to many of water’s unique and important properties!
The polar water molecules orient to one another and are held together by the electric attraction of opposite charges, which you can see in the illustration above.. This is important for us: If this were not the case, water would not be a liquid at room temperature at all! The relatively light water molecules would fly off as a gas because the molecules would have no attraction between them. Without this very important property, there would be no life as we know it. This attraction of water molecules to one another is called cohesion. They can also stick to many other objects by the same process, a property known as adhesion.
These two properties come together in the video above. The water molecules stick to the string, but also to one another. This allows the water to be poured at strange angles, and none of it would happen if it wasn’t for that fascinating little molecule, dihydrogen monoxide.
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!
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 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!
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!
We soaked this $5 bill in flammable rubbing alcohol and then lit it on fire. So how did it survive? Does it have something to do with the bill itself?
This demonstration is impressive with money, but we haven’t been able to find an example of it using other materials. Many people have asked us what would happen to regular paper in the same situation. This opened up the chance for us to do some real science! We repeated our experiment, replacing the dollar bill with standard white paper and a brown paper napkin. Neither of these caught fire either.
The key to this trick is the part that stayed the same in all three experiments: a solution of rubbing alcohol and water. Water has a high specific heat, so changing its temperature takes a lot of energy, as we’ve seen before. Unlike water, rubbing alcohol is very flammable. It easily burns away until most if it is gone, leaving behind a mixture consisting primarily of water.
By lighting pools of alcohol on our fireproof table tops, we measured the temperature of the water left behind after burning off as much of the alcohol as we could. Here are the results:
Despite being literally covered in fire for thirty seconds, the water temperature only climbed by 11.8 degrees Fahrenheit! The water in the rubbing alcohol mixture is protecting the money with its high specific heat, preventing the paper in all of the above examples from getting hot enough to burn. As such, when performing this experiment, it’s very important that we completely soak the money (or other experiment subject). If any surface is exposed, it will catch on fire! After the flame has gone out, the paper doesn’t even feel warm to the touch.
Only try this at home with adult permission and a fire extinguisher!
Light travels incredibly fast. In a vacuum, it speeds along at nearly six trillion miles per hour. Ever notice how your feet look distorted when you wade in the water, or how a straw seems to be cut in half where it enters a full glass? When light travels through a medium, it slows down. When a collection of light rays crosses from one material to another (from water into air, for instance), the change in speed warps the image.
This warping effect can appear random, as in the case of rippling water, or it can be well-organized. We often take advantage of light’s transition between air and glass, for example, to bend images in a useful way. A magnifying glass works by taking a small image and spreading it out over a large area. What happens when you use it backwards– put a large cross-section of light in, then focus it down to a tiny point?
Try this with the sun as a light source on a warm day, and you’ll find that the visible light and heat at the focus point are intense enough to burn wood!
As far as we can tell, the ocean has been slightly basic for hundreds of millions of years. However, that seems to be changing, and the culprit may surprise you. Everyone has heard of carbon dioxide. It’s the thing we breathe out, what plants crave, and there’s this thing called the greenhouse effect which you’ve probably heard of by now.
CO2 concentrations have certainly changed in the past based on our examinations of ice core samples. However, they are certainly on the rise now. Credit: NASA, UCR, RUSD
What we do know for sure, is that carbon dioxide is on the rise. While the most often talked about consequence of this is a trend of increasing global temperature, there is another important concern, and it has to do with our water. There are many ways that we can measure water including temperature, pollutant content, clarity, and salinity, but this particular issue focuses on acidity.
Water is made up of two parts hydrogen and one part oxygen, leading the the chemical formula H2O. In pure water, these molecules occasionally break apart due to the following reaction:
On the left side, we’ve got our old pal water. In the middle, the double sided arrow means that this reaction can go both ways, depending on the ratio of water to its parts. Pure water is neutral, meaning that this reaction is the only source of H+ and OH– ions1 in the water. If anything throws this balance out of whack, the water will become basic if more OH– ions are added, or acidic if more H+ ions2 are added.
So what does all of this have to do with carbon dioxide (CO2)? When the CO2 gets in contact with water–which covers most of the Earth–it combines with the H2O by the following reaction.
This forms Carbonic acid, which then donates its extra hydrogen to the water like this:
In the previous paragraph, we talked about how anything that can add H+ to the water will cause it to become acidic. The resulting molecule above is known as carbonic acid because it has these extra hydrogen ions to donate.
While this all seems pretty abstract, you can watch it happed below. This water is poured over dry ice or solid carbon dioxide. Solid carbon dioxide turns directly into a gas at room temperature. The water also has an indicator solution that will cause it to turn from neutral green to red if it is acidic, and blue to deep purple if it is basic.
We measure this using the PH scale, which runs from zero to 14 with low numbers indicating higher acidity. It is also a logarithmic scale, which means that changing from a seven to a six on the scale corresponds to an increase of ten times to the acidity! For the past 300 million years, the ocean has been at a steady–and slightly basic–PH of 8.2. Over the past 200 years, it has dropped to about 8.1, which doesn’t seem like much on this scale, but corresponds to an increase of about 30% to the number of acidic ions in water. Even without further increase to atmospheric CO2, this trend should accelerate to a PH of 7.8 by the year 2100, an increase in acidic ions of 126%!
What does all of this mean for us living on Earth? No one is quite sure. Most organisms can only tolerate a narrow range of acidity, and there are many species that live in the ocean. Simulating these conditions in a lab is pretty easy, so we can identify some at risk species right away. Coral reefs, in particular, are known to be very sensitive to acidification.
Dissolved carbon dioxide can interfere with the calcification process that allows shells and exoskeletons to grow. Over the course of 45 days, this sea butterfly slowly dissolves in a lab simulation of acidic ocean water. Courtesy of David Littschwager/National Geographic Society. Similar research continues today.
Ions are just atoms or groups of atoms with a net charge, meaning they have an extra electron if negative, or lack an electron if positive. Ions are much easier to dissolve in water than neutral molecules.
Note: The freed hydrogen ions will actually combine with surrounding water molecules, forming Hydronium (H3OH+) which is usually denoted H+.
With things heating up this summer, we wanted to just play in the snow! The stuff you just saw is called sodium polyacrylate. It is also known as waterlock, which shouldn’t be surprising considering what you just witnessed! Its ability to absorb an incredible amount of water makes it useful for certain purposes–like diapers and thickening agents–but it can also make for a super fun science project!.
We used about 30 grams of sodium polyacrylate, and poured about 1000 grams of water into it! Since all of the water was absorbed, the 30 grams of sodium polyacrylate became about 34 times heavier! The average adult in the US is about 180 lbs. For them, this would be the equivalent of going swimming and coming out at over 3 tons, which is about the size of a small adult Orca!
Even after absorbing all of that, the snowy substance felt damp, but still could have absorbed more! Sodium polyacrylate has been called a super absorber for the fact that it has been known to absorb up to 300 times its own mass!
An interesting chemistry note: adding salt to the water and snow mix changes the properties of sodium polyacrylate immensely. Check it out below as the salk breaks down the mixture, resulting in truly wintery pile of wet, sloppy slush.
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!