CAUTION:Antifreeze is a very powerful chemical that, if ingested, can cause serious illness or death. Do not attempt to use it without adult supervision. All appropriate safety precautions have been taken for the filming of this video.
If you are from a colder part of the world, then you know how important antifreeze is. It is mainly used for pipes in homes and cars. But it no longer becomes useful if it itself freezes. Can that happen?
Antifreeze is a substance that lowers the freezing point of water, protecting a system from the ill effects of ice formation. The purpose of antifreeze is to prevent a rigid enclosure from bursting due to expansion when water freezes. Water usually freezes at about 0˚C or 32˚F, but when antifreeze is added to it that changes to being able to freeze at about -50˚F.
Knowing this, we wanted to see the affects if we poured some into liquid nitrogen and pour liquid nitrogen into antifreeze.
It turns out that it freezes, but in a weird way. It actually takes a long time for the antifreeze to freeze. The -321˚F liquid nitrogen does the trick, but will take more than a minute to freeze it all the way through, compared to water which takes a few seconds. The solid antifreeze is not uniform, and does not look like the liquid. It is opaque compared to the clearish liquid, and almost cloud like in shape!
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!
It wouldn’t be surprising if nitrogen was your favorite elements. N2 is the most common molecule found in our atmosphere, making up roughly 78% of it. But here at camp, we have a different reason for why it is one of our favorite things to have around. We have a ton of liquid Nitrogen on camp and love using it to freeze things. We wanted to see what would happen when an LED (Light Emitting Diode) was submerged in the -321˚F liquid.
It turns out that something pretty cool happens… it changes colors! But why would cooling it down, taking energy away from the LED allow the color to change in a more energetic direction?
To answer that we need to know how LEDs work. They aretwo-lead semiconductor light sources that emit light when activated. When a suitable voltage is applied to the leads, electrons are able to recombine with electron holes on a positive or negative band within the device, releasing energy in the form of photons.
When an atom is at rest it’s electrons are at the lowest energy state possible. With LEDs, an electron is shot in, hits another electron which increases its energy, hopping up to the opposite band. When it starts to rest enough, it falls, giving off a photon (light particle). The bigger the hop in energy state, the greater the fall will be, and therefore the more energetic the photon will be.
The electrons start off with a bit of thermal energy, but when submerged in the liquid Nitrogen some of the thermal energy is removed. When the thermal energy is removed it allows the distance between the bands (the band gap) to physically increase which in turn will increase the fall of the electron, increasing the frequency of light!
Liquid nitrogen is super cold, -320 degrees Fahrenheit, but what if we could cool it down further or even freeze it into nitrogen ice? Watch this video and read more to find out!
The solution lies in a summer day at the pool, sweat, or at least something tying them: evaporative cooling. When you get out of a pool and the water evaporates off of you, it is actually taking heat away from you because evaporation is something called an endothermic process, or something that takes heat energy away from a system. That’s actually the entire point of sweating; your sweat evaporates, cooling your skin.
Now, liquid nitrogen boils and evaporates at room temperature, but that process is too slow to cool it enough to freeze. We need to use evaporative cooling to bring it down from -320 to -346 degrees Fahrenheit, which means we need a lot more evaporation in a shorter period of time. For this, we turn to our vacuum chamber.
Inside the vacuum chamber, air pressure is dropping to nearly zero, so the liquid nitrogen boils away faster due to the ideal gas law. When pressure of a system decreases but temperature remains the same, volume must increase; this means more liquid is transitioning to the higher-volume gas. As the liquid nitrogen boils away faster and faster, it cools down the remaining liquid nitrogen until it eventually reaches the freezing point of -346.
This solid nitrogen can’t stay, however. Once we equalize pressure inside the vacuum chamber with the outside, it reverts back to its liquid state. This method of producing solid nitrogen is actually the primary way of creating it in laboratories here on Earth. Out in space, solid nitrogen can be found on the surface of Pluto and Triton, one of Neptune’s moons.
CAUTION! Do not try this at home. This experiment uses liquid nitrogen which is EXTREMELY cold. Safety precautions were taken in the filming of this video.
Many know that liquid nitrogen is extremely cold, at -321ºF. When it is exposed to extreme temperature differences, you can observe something called the Leidenfrost Effect. To learn more about the Leidenfrost Effect click here. Once the insulating barrier from the Leidenfrost Effect goes away, then the liquid nitrogen will boil.
Due to the liquid nitrogen boiling, it will produce a lot of gas. Gaseous nitrogen has a lot more energy than liquid nitrogen resulting in a rapid expansion and pressurizing of the gas. While the bottle is right side up, the gas can easily expand and escape the bottle through the nozzle. However, when flipped upside down, the gas has nowhere to expand to which pressurizes the bottle, forcing the water down and out of the bottle.
Newton’s’ Third Law says that for every action there is an equal and opposite reaction. The water being forced to travel downward results in sending the bottle skyrocketing upwards! How high do you think this rocket launched?
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.
Where do stars come from? The short answer is: gravity. All objects with mass experience gravitational attraction to each other. That includes you & the Earth, you & me, every person on our planet, and every star in the cosmos. So, why aren’t we pulled in all directions? Gravity depends on two things: mass and distance. The bigger an object is, the stronger its influence. The farther it is from you, the less you’re affected by its pull. Stars have plenty of mass, but they’re so far away that their gravitational effect on us is negligible. You and I could stand next to each other, but we just aren’t massive enough to pull significantly on each other compared to the much stronger attractive force Earth exerts on our bodies.
The Great Orion Nebula, visible to the naked eye as part of Orion’s dagger, is a massive space-cloud system and a productive stellar nursery. Image credit: UMass/2MASS/IPAC
In deep space, it’s a different story. In the absence of larger gravitational influences, even dust particles pull each other closer. It’s this quiet, dark, and delicate dance that gives rise to the stars we see in the night sky. Nebulae are massive space clouds of gas and dust. Within these clouds, turbulence makes some areas denser than others. When a dense knot of dust reaches critical mass, it collapses under its own gravitational pull, heating up and becoming a protostar. This spinning collection of hot, dense debris drags nearby particles along with its rotation, and an embryonic solar system is formed.
Einstein’s theory of relativity describes spacetime as a three-dimensional fabric that can be stretched in a fourth dimension. The way that massive objects stretch the fabric of spacetime explains their gravitational pull on each other. That’s tough to visualize, but a two-dimensional model that stretches in 3D helps us to wrap our heads around the idea.
Particles of water vapor model the behavior of dust in a nebula.
When we place a heavy sphere in the center of a sheet of stretchy fabric, it pulls the surface down. Drop marbles or BBs onto the fabric and they spiral around and around before coming to rest at the lowest point. The same thing happens with water vapor: it spirals to the spot where the gravitational potential is lowest– the heavy object in the middle.
This model of spacetime provides a simple, fairly accurate illustration of the way individual stars form in nebulae.
Why does water form lakes and oceans underneath a vast expanse of airy sky? The answer to that, and many more questions, is density! Density is most easily described mathematically by the following equation: This means that density depends on only these two quantities: Mass, or the amount of matter that something is made up of, and volume, a measure of how much space it takes up.
Most of us have heard of density in relation to things floating in water, but it also works for air. Seeing whether or not something floats in another thing is a great way to compare the density of two substances. Here, we can see that a balloon filled with nitrogen is more dense than air. Air is mostly made up of nitrogen, so it is mostly the additional weight of the balloon itself that causes it to fall to the ground. Alternatively, the helium balloon floats upwards as it is so much less dense than the surrounding air that the comparatively heavy rubber balloon is dragged up along with it. These two objects have the same volume, but their densities differ because of their mass.
The other quantity that we can look at is volume. If the volume becomes smaller, but contains the same mass, the density will increase. Alternatively, increasing the volume will decrease the density. In this demonstration, we take advantage of a property of gases described by Charles’s Law, which states that if we change the temperature of a gas, its volume will change proportionally. By lowering the temperature of the helium balloon with liquid nitrogen, we decrease its volume. This raises its density to be above that of air…until it warms up and expands back to a low enough density to again take flight!
This concept can help to explain many things, even if they seem odd at first. Clouds are made of water, but hang in the sky! It might seem like this is just because clouds are light, but the average cumulus cloud weighs over 1 million pounds! That is definitely not light, but they are light for how big they are, and they are big. Clouds are made up of water, but this water is very spread out. The volume is so big that this 1 million pounds of cloud actually weighs less than an equal amount of air would, even though we always think of air as being pretty light!
However, as this air rises it cools and gets closer together just like the balloon dunked in liquid nitrogen. Eventually, these water molecules band together as they get cold. When enough of the molecules stick together, they get to be more dense than the cloud around it, and plummet back to earth as precipitation.
By the way, the average person is a little less than a thousand times more dense than air. This means if you were 10 times taller, wider, and thicker but not any heavier, you would float like a balloon! Please don’t try this at home.
Every step you take is a tiny study in rocket science! Lift one foot and push backwards on the floor with the other. The floor exerts an equal and opposite (forward) force on the planted foot, and your body moves ahead.
Equal and opposite force pairs are everywhere. Stand on an ice rink and push against the wall; the wall pushes back, and you slide away. Sit in a chair, and your body pushes down against the seat, which pushes up with precisely the same force– if it didn’t, you’d fall! Birds push down on the air with their wings, and that air pushes their bodies upward.
Image credit: NASA
The same process propels a rocket in motion. Thrusters shove fuel out behind a spacecraft. The fuel pushes back, equally and oppositely, and the rocket moves forward. Actual rocket fuel is accelerated backwards by explosive chemistry. We can model spaceflight in the lab with any expanding fuel whose flow can be directed.
Liquid nitrogen boils into gaseous form at -321 degrees Fahrenheit. This means if it is warmer than that, it will turn from a liquid to a gas that takes up 694 times as much space. We trapped this nitrogen in a ping pong ball with two very small holes on the sides. When the nitrogen expands, this is the only way out! The holes are positioned in opposite directions on opposite sides, and as the gas is directed out of these makeshift nozzles, the equal and opposite force due to Newton’s Third Law accelerates it to truly incredible speeds!
Actual rockets are meticulously designed for optimum aerodynamics and equipped with fins for stability. Ping pong balls are pretty much the opposite of that! Our tabletop rocket is all over the place. With some structural modifications, more stable motion might be possible. For now, though, we’re just having fun with this nitrogen-powered turbo top!
Glow sticks are chemical reactions waiting to happen! Most are made of an outer plastic casing with a small glass capsule inside. The outer tube is filled with dye, which determines the color of the glow stick, and a chemical called diphenyl oxalate. The glass within contains hydrogen peroxide, the same thing you might use to clean out a cut or scrape.
When you crack a glow stick, you break the glass inside. Its ingredients are then free to mix and react, releasing carbon dioxide and chemical energy, which is converted to visible light. The reaction takes some time, which is why the glow lasts a while. The ratio of compounds in a glow stick determines whether it shines brightly and briefly or more dimly for a long time.
Temperature is another great way to control chemical reaction speed. When we add energy by heating up the glow stick reactants, the molecules move faster and interact more often. Cooling the system takes energy away, literally slowing things down at a microscopic level. Clear containers of cold, warm, and boiling water give a great view of this chemical property!
The fourth flask, on the far left, contains liquid nitrogen. At -321 degrees Fahrenheit, this cryogenic substance is so cold that it actually stops the luminescent reaction, making the glow sticks go dark. We can bring them back to life by allowing them to absorb energy in a warmer environment.
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