# Leiden-frost Nipping at Your Toes

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)!

Heat rises, boats float, clouds hang listlessly in the sky, and icebergs aimlessly bob around the ocean. All of these things happen because of the same scientific property: density!

Density is a rather simple property. It depends on two things, mass and volume. Mass is basically how much something weighs, but something still has the same amount of mass weather it is on Earth, Jupiter, or out in space where its weight would change dramatically. Volume doesn’t have anything to do with how loud something is, but rather with how much space it takes up. Mathematically, an object’s density is equal to its mass divided by its volume.

The demonstration here using the pipette in a bottle of water is a great way to buoy your own understanding of density. The pipette is carefully balanced to barely float in the water. However, by squeezing the bottle, water is forced up into the pipette. This makes the pipette heavier, which raises its density. Releasing the bottle down the opposite. For another cool example of density, click here!

By simple comparing the density of different things, we can tell if they would float or sink in water or air or anything else that has a known density. This is incredibly useful and can lead to some fun facts. For example, Saturn is less dense than water. That is to say it would float in a bathtub, but it might leave some rings! Red giant stars, like the famous Betelgeuse, are actually less dense than air! They are incredibly heavy–Betelgeuse weighs in at about 18 suns worth of mass–but they take up so much space that they are essentially GIANT balloons!

The sun would not float like a balloon now, in fact it is currently much more dense than water. However, given 5 billion years it will enter the red giant phase of its own life and grow in volume by about 800 million times! This will decrease its density so much that it goes from 40% higher than water to lower than air! As you can clearly see, density is not necessarily a constant property of something, it is actually something that can change.

One of the most commonly accepted consequences of density is that heat rises, but that isn’t technically true. It would be more correct to say that heat rises on Earth. This is because as things warm up, their volume increases which lowers their density. However, if we leave the friendly confines of Earth, this is no longer true! In the microgravity environment aboard the International Space Station, there isn’t really an “up” or “down”, gravitationally speaking. That makes it hard to decide what “heat rises” even means! Fire gets equally confused. Check out this comparison between fire on Earth and aboard the ISS from NASA.

# DIY: Fascinating Properties of Dihydrogen Monoxide

Humans are approximately 60% dihydrogen monoxide. If this is alarming, it might be helpful to know that this is just waterWhile 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.

# What’s the Matter: Is Fire a Plasma?

Is fire a plasma? Turns out it’s not a trivial question! The answer depends on how you define the parameters of the fourth state of matter. Descriptions of plasma commonly include the following points: plasma is what happens when a gas is subjected to lots of ionizing energy. Although thoroughly ionized, it is quasi-neutral. Its molecules display collective dynamics and respond as a group to electromagnetic influence.

The sun as seen by NASA’s IRIS orbiter. Ultraviolet image translated into false color for human consumption. Stars, including our sun, are made of plasma.

Most of the observable universe is made up of plasma! Astrophysical plasmas are mind-blowingly hot. On Earth, too, plasma is created by copiously applying heat or otherwise energizing a gas, although plasmas can also be created in laboratory scenarios that are cold by human standards.

So, which state of matter does fire belong to? Depending on who you ask, a flame is either a low-level plasma or a lightly ionized gas. A flame is a heated volume of air in which some electrons have broken free from their nuclei, but it’s not hot enough (or ionized completely enough) to enable cohesive electrodynamic behavior on the level of, say, an arc welder.

Plasma or not, the gas within a flame contains enough ions to make it a decent electrical conductor! Here, electricity arcs from a generator to a candle flame.

# Collisions!

Newton said that for every action there is an equal and opposite reaction.  Collisions are the thing that happens when two objects slam into each other!  But what does that mean for science?  Well, depending on the object’s material(such as using silly putty vs using marbles, skee balls, or shots), mass, and vector (magnitude and direction) it can mean a few things.  There are two different types of collisions that we can witness on a daily basis.  Inelastic and elastic collisions.  An inelastic collision is a collision that has a conservation of momentum, but not kinetic energy.  Whereas an elastic collision conserves both kinetic energy and momentum.  There are different types of energies.  Kinetic energy can be thought of as “moving” energy.  There is also potential energy, rotational, thermal, gravitational, chemical…the list goes on.

Momentum is defined as the strength or force that something has when it is moving. Most ordinary collisions that you witness are considered inelastic because of the sounds you hear (sound=type of energy -> total kinetic energy – sound =loss of kinetic energy), or the heat released (same as above)..  The most elastic-like collision is when two billiard balls collide (or like in our experiment)  they are technically inelastic collisions because the loss of energy in the sound, but that energy is negligible (meaning that it doesn’t matter a whole lot).

To play around with different outcomes of mostly elastic collisions you can change a few variables such as mass, density, and velocity (speed and direction).  We used some similar sized objects, and then some extremely different sized objects to test this out.  We also changed the angle of impact to see where the different objects would end up after impact.  It turns out that a slight angle change makes a big difference due to the curvature of the balls.  This is something that professional billiards players have to take into account at every shot.  The speed of the objects just before impact makes a huge difference also. If you try to collide the two objects with a slow enough velocity then the objects may just travel together.  On the other hand if you slam them into each other you might see that there is a nearly complete transfer of the kinetic energy from the first object to the second.

# Recycling: Turning Styrofoam to Glue

Today is America Recycles Day, which you can learn more about recycling here. We wanted to take this opportunity to learn something cool about one of the most heinous landfill residents: styrofoam. This lightweight convenient insulating material has found many uses, from takeout containers to disposable coolers. Unfortunately, to go along with all of its good qualities, it has one bad one: it doesn’t degrade naturally. This means that when it goes in the trash, it will stay there for a very long time. In addition, styrofoam is about 95% air, each pound that is disposed of will be taking up a lot of space–possibly up to 30% of the total volume–in our garbage for the foreseeable future.

Fortunately, not everyone is resigned to this fate. Instead, people have been trying to come up with a better way to deal with this. One of these ways uses acetone. Acetone is an organic molecule made up of carbon, hydrogen, and oxygen, and is the simplest member of the ketone family. On the right is a picture of acetone at the atomic level.

Most of the uses of acetone revolve around a single property: it is an excellent solvent. This means that it does a great job of dissolving many different kinds of molecules, making it useful as a cleaning agent in chemistry labs and a remover of nail polish.

Styrofoam is made of polystyrene, which in itself means a chain of styrene. Styrene is a relatively simple organic molecule that can easily bind with itself. When it comes in contact with acetone, the polystyrene chains fall apart. However, the acetone doesn’t actually dissolve the styrene molecules. If it did, all of the styrofoam would disappear into the acetone, but instead we end up with this.

Depending on your point of view, this probably looks like some combination of gross, scientific, and fun. Additionally, it is also useful. Using solvents like acetone to break down styrofoam can repurpose it to being a rather useful adhesive. Being able to use styrofoam as a glue is a terrific alternative to having it fill up or landfills.

# How Spinning Magnets Make the World Turn

We all know know what magnets are. At the very least, you’ve probably put one on the fridge. Magnets can come in all shapes and sizes, but they all work the same way. In simple terms, they have a north pole and a south pole. When two identical poles get close, they repel, and–of course–opposites attract.

Some of the many shapes, sizes, and types of magnets. Photos from coolmagnetman.

That said, many things about magnets are a lot more mysterious. Scientists explain these phenomena through something called a magnetic field, and this has some pretty wild and testable consequences. One of them is known as Faraday’s Law, which says that a changing magnetic field can generate electricity through a process known as electromagnetic induction. There isn’t a lot to be said about how this works; just as gravity pulls you down, moving magnets near wire will make electricity!

If this doesn’t seem all that interesting or important then just think for a moment about how much electricity we use. Then consider where that electricity comes from. Coal, wind, and nuclear power probably come to mind–but then how do we get the electricity out of those things? The answer is actually simple: magnets! Each of the major methods of making electricity really are just finding ways to spin a turbine which is connected to a magnet!

The amount of power that you get out of one of these generators depends on how many times the wire is wrapped around, how close it is to the magnet, and how strong the magnet is. This in turn makes the magnet harder to turn. If you look at a windmill, you will notice it has huge blades, allowing it to convert more wind into more power!

This wind farm in Palm Springs not too far from our campus employs this exact technology to generate electricity from the wind! Photo from best of the best tours!

# Refraction: How To Bend a Laser Beam

Light travels at different speeds through different media. Water slows light down more than air, for instance. Corn syrup slows it down even more than water. In this experiment, we create a gradient solution of sugar water in a tank. As a laser beam travels through the liquid, the changing concentration bends its path!

The solution at the bottom of the tank is about 80 percent sugar by volume. As a siphon slowly transfers liquid into the aquarium, we add more and more water to the top container, diluting the mixture. The last layers to be added contain almost no sugar.

Sugar water is denser than pure water. This property keeps the heavier, more concentrated solution on the bottom of the tank. Lighter mixtures float above in order of density. We chose a siphon system to stack our liquids because it transfers the fluid slowly and gently, without creating too much turbulence. This method allows a relatively smooth density gradient to form.

Our variable solution of sugar water also has a gradient index of refraction, meaning that light travels faster in some parts than others. Namely, light is slowed down the most in the heavy 80% region towards the bottom. It travels faster as the mixture becomes more dilute near the top of the volume of fluid.

Imagine a line of children holding hands and running across a field. If they all run at the same speed, the line stays straight. What happens if they’re not all identical athletes, and you place them in order of running speed? The line bends. One end of the chain ends up ahead of the other. This is a bit like what we’ve done to the laser beam.

Written By: Caela Barry

# Diffraction of Light

What is light? It seems like a simple question, but many people struggle to answer it. That’s okay! The famous Albert Einstein received the Nobel prize for his work in answering that exact question. As you might expect, the answer isn’t all that simple.

Light is a part of the electromagnetic spectrum, which is made up of electromagnetic waves. As the name suggests, this means that light is made up of small changes in electric and magnetic fields, like this!

These electromagnetic waves can carry drastically varied amounts of energy. In fact, when you look at different colors, your eye is separating out the energies for you. The only difference between red and blue light is the energy of the light! To understand color as energy, let’s look at one of the most revealing properties of an electromagnetic wave: its wavelength.

The energy of the wave depends on this factor alone. The longer the distance between the wave crests, the lower the energy of the waves. The closer together they are, the higher the energy. Across the electromagnetic spectrum, wavelengths vary tremendously, from low energy radio waves the length of a school bus to high energy gamma rays even shorter than an atom! There is nothing particularly special about visible light. It’s just another electromagnetic wave. One wavelength of visible light is about half the size of a small bacteria. That just happens to be what human eyes can detect!

The image above shows different kinds of electromagnetic waves and their wavelengths. In gray, you can see how much of each kind of wave is blocked by the atmosphere.

Diffraction gratings are a great way to separate wavelengths. When used to filter white light, the diffraction grating splits up the different energies into a rainbow! When applied to various gases in the video, it shows a unique pattern of light for each one. Since each element produces a different pattern of light, scientists can determine what something is made of just by looking at the spectrum from that object!

This is how scientists know what the sun is made out of. It would be difficult to go retrieve a sample from the surface of the sun for fairly obvious reasons. Similarly, astronomers have been able to use this knowledge to find out what makes up other stars, galaxies, nebulae, and even other planets! Every bit of knowledge that we have about everything outside of our solar system comes directly from observing and analyzing light.

# From Apples to Inertia

One day, Isaac Newton was sitting underneath a tree, and an apple falls and bonks him on the head. In a stroke of genius and coincidence, Isaac comes up with the theory of gravity and the rest is history…or so the story goes. This simple anecdote actually does a disservice to just how much of a contribution Isaac Newton made to the core of science. While there are many subjects to pick from, today, we are going to focus on the first of Newton’s Three Laws of Motion.

As many of us learned from another famous scientist, Bill Nye, inertia is a property of matter. This is also Newton’s First Law of Motion, and it is actually a very simple concept: an object at rest or in motion will remain at rest or in motion unless acted upon unless something makes it move or stop. So why did it take someone like Isaac Newton–the guy who invented Calculus just to help him understand gravity–to come up with it for us?

The main reason is that in our experience, the law seems wrong. If you throw a ball, it doesn’t keep going forever. It hits the ground and stops rolling after a bit. If you start walking, you don’t just glide on forever. This does not break Newton’s first law though, and that is because there are little forces like the air and the friction of rolling a ball that slow them down. These outside forces are exactly what the law is talking about! If instead you were to throw a ball out in space, it would keep on going forever until it hit something or got pulled in by gravity!

In these demonstrations, we are showing that an object at rest remains at rest. The little metal hex nuts sitting on top of the orange ring are stationary directly above the small opening of the bottle. When the ring is pulled out, the hex nuts do not move horizontally, and instead fall straight down due to gravity!

This idea can be expanded to the table cloth magic trick that you may have seen, but  you have to get it just right!