Have you ever wondered what electric lighters and Wint-o-green Lifesavers have in common? No? Well we here at AstroCamp wondered exactly that and the answer is a surprising one: they both involve energy released from crystals!
Electric lighters like this piezo ignitor don’t use the normal flint and steel ignition method of a normal lighter, and they don’t have a gas reservoir. Instead, they use a spark produced from a piezoelectric crystal (a crystal that releases a small electric charge when compressed, warped, or otherwise physically manipulated) to light a stream of gas coming from a stovetop or grill. When you press the button, a hammer strikes the crystal, releasing an electric charge that travels along the lighter until it lights the gas.
However, a different process is happening within the mints: triboluminescence. When you bite into the Lifesaver, you break apart the sugar crystals, which release small amounts of ultraviolet light. Ordinarily, this would be unobservable, as our eyes can’t see UV light, but the wintergreen oil inside the mints fluoresces under UV light. As a result, whenever one of those small pops of UV light are released, the oil absorbs that light and re-emits it in the form of visible light. It may look like sparks are being released, but unlike the piezoelectric ignitor, no electricity is being produced.
The ides of energy released from crystals may seem like something out of science fiction, but grab some mints and see how real it is.
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.
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)!
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!
Electric generators change mechanical energy into electrical energy. An electric motor does the opposite: it changes electrical energy into physical motion. This conversion is possible because of the Lorentz force.
Electricity is just the movement of electrons through a loop, called a circuit. Ever notice how magnets can repel or attract objects without touching them? When a circuit carries electrons near a magnet, the magnetic field pushes those electrons sideways.
The Lorentz force is strongest when the magnetic field and current-carrying wire are perpendicular to each other. Electric motors use this arrangement to turn electrical energy into mechanical motion efficiently. It’s easy to see for yourself, too! All you need is a magnetic field and a circuit that’s free to move. In today’s experiment, we’ll show the Lorentz force in action with a magnet, a battery, and a length of wire.
Start by setting the negative end of an AA battery on a strong magnet. Magnetic field, check; power source, check. Mold a length of wire into any shape that can balance on the positive end of the battery while also touching the magnet, completing a loop of conducting materials. Given a circuit to flow through, electrons begin to move, and voila! You’ve got a current flowing through a magnetic field. The current and the field are nearly perpendicular to each other where they intersect. The Lorentz force pushes the electrons, and the conductor they flow through, off to the side.
Shape the wire so that it can balance and spin on the positive terminal, and the electromagnetic push induces rotation for as long as the battery’s charge lasts. Electrical energy becomes physical motion. Congratulations– you’ve just created a motor!
Thomas Edison famously invented the incandescent light bulb. These light bulbs are pretty simple things. They are really just a glass casing around a tiny metal resistor called the filament. As electricity runs through it, the filament heats up until it produces light. But how much does it have to heat up? It turns out to be a pretty interesting question.
Incandescent light bulb. The filament is the horizontal piece in the center of the bulb. Image credit: Encyclopædia Britannica
Everything gives off light based on its temperature, but not all light is the kind we can see. That part, known as the visible spectrum, is a tiny part of the larger electromagnetic spectrum. These different kinds of light are separated by their energies, which can be described with wavelength.
Where is a simple equation that allows us to find out what wavelength is given off by an object at a given temperature. It’s called Wien’s Displacement Law.
Humans are about 90 degrees Fahrenheit, which is about 305K. To find the wavelength emitted by humans, all we have to do is divide .002898 by 305. This gives about 9500 nanometers (nm) which is what we measure wavelength in for visible light. Visible light is between 400nm and 700nm, so 9500nm is pretty far away from that. This puts it squarely in the infrared.
The full electromagnetic spectrum, including the very small visible light portion. Credit NASA
So how hot does that filament need to be to give off visible light? Lets aim for 500nm, which is definitely in the visible light range. By using algebra, Wien’s Displacement Law can be rearranged to T=b/. Dividing b by 500nm gives a temperature of 9973℉, which is about the temperature of the surface of the sun!
This actually makes total sense too! This means that the sun’s primary light emission is smack dab in the middle of our visible spectrum. It definitely makes sense that if we were to gain the ability to see, it would be to see the kind of light that was the most common. However, pretty much everything in the sun is a plasma due to the immense heat. There is no way that a light bulb could survive such insane temperatures.
Light bulb filament comes in at a relatively cool to the sun but still insanely hot 4500℉. Throwing this back into the equation, we get 1052nm, which is much closer to the 400nm to 700nm range. The primary emission is still in the infrared. However, this only gives the peak wavelength of light given off. The actual light is a mix of light more like this:
For a light bulb, only about 5% of the energy is given off as light that we can see. The rest of it is mostly given off as infrared light, or heat which is why these bulbs feel hot. The reason they don’t feel like 4500℉ is that the inside of the light bulb is a vacuum–meaning it contains no air–and the heat thankfully doesn’t conduct through it very well. They actually use this vacuum insulation for water bottles, thermoses, and even the Dewars that hold things like liquid nitrogen!
This inefficiency is the reason behind moving to much more eco-friendly fluorescent light bulbs. These bulbs don’t use Wien’s Displacement Law to produce light, but instead are filled with atoms that naturally release light when hit with a bit of electricity. Even many new bulbs that look like incandescent bulbs actually contain several small Light Emitting Diodes, or LED’s inside which share the energy efficient qualities of fluorescent bulbs. What a bright idea!
WARNING: Handle dishes with a potholder, and be aware that they may break if left in the microwave too long. Always keep a fire extinguisher on hand when experimenting with high-energy science.
What do lightning, the aurora, neon signs, and grapes have in common? Plasma! It might be the least familiar of the four states of matter (solid, liquid, and gas are the other three), but it’s actually the most common form of matter in the universe. It’s what stars are made of!
This 2002 coronal mass ejection (CME) on our sun blasted plasma out into space at millions of kilometers per hour! During periods of high solar activity, it’s not uncommon for scientists to observe 2 or 3 CMEs per day. Image credit: NASA
Plasma is what we get when we apply enough energy to a gas to strip molecules of their electrons. This energy typically comes in the form of heat or a strong electromagnetic field like lightning. If you have access to a microwave, you have a great source of electromagnetic waves to work with! Normal microwave use doesn’t produce plasma, though– it takes an antenna to create a strong, steady field.
A microwave heats food by barraging it with electromagnetic waves, causing the molecules inside to vibrate (see previous post for more in-depth microwave science). In this experiment, we’re interested in the waves themselves. A typical microwave oven radiation wavelength is about 12cm, or just under five inches. A line of four grapes is about five inches long. Thanks to this ratio, a grape makes a great antenna for our DIY plasma project!
Here’s why it works: a half-wave dipole antenna is an antenna made of two matching parts, each about ¼ the length of the wave the antenna is supposed to receive. This style of antenna does its job so well that it’s the standard in radar technology and other fields. You may even have seen it in your living room as “rabbit ears” on a television! Conveniently, grapes conduct electricity well, and a typical grape diameter is about ¼ the size of a microwave oven wavelength. This makes two grapes next to each other (or one halved grape) an ideal antenna for concentrating the waves inside the oven. The grape antenna creates a strong, uniform electromagnetic field… exactly what we need to strip gas molecules of their electrons. Give the field a little time to gain intensity, and BZZZT! Plasma! DIY style!
Have you ever felt pressure on your body– especially in your ears– as you swim deep underwater? The deeper you go, the more pressure you feel. This is the core of a principle called buoyancy. Buoyancy explains why, in a liquid, what goes down just might come up!
Let’s think about how water affects this metal sphere. Pressure increases with depth, so the water at the bottom of the sphere pushes it up more than the water at the top pushes it down. The same goes for you – when you float vertically in the water, the pressure is always greatest at your feet. This unbalanced force, called buoyancy, is illustrated here:
Photo courtesy of http://hyperphysics.phy-astr.gsu.edu/hbase/pbuoy.html.
Buoyancy doesn’t care how heavy things are, just how much space they take up in the water. The buoyant force lifting an object up is always the same as the weight of the liquid that would normally occupy that space. If you push a beach ball underwater, the buoyant force pushes back with the weight of the water that the beach ball has shoved out of the way. Push a yoga ball under, and you’ll feel a push back equal to– you guessed it– the weight of a yoga ball full of water!
So, why do some things float and others sink? We can think of the answer as a battle between the forces of buoyancy and gravity. A rock is heavier than the amount of water it pushes out of the way. Gravity pulls down more than buoyancy pushes up, so the rock sinks to the bottom. A beach ball, on the other hand, is much lighter than a beach-ball-sized blob of water, so in this case buoyancy beats gravity. It floats! In general, if an object is less dense than water, it floats. If it’s more dense, it sinks.
In our Coke can experiment, we see that regular Coke is denser than diet. The sugar in the red can drags it to the bottom of the tank.
Buoyancy works in other substances, too. A helium balloon floats in air for the same reason a beach ball floats in the pool. Water stays in the pool because it’s more dense than air– if it wasn’t, it would float to the ceiling!
How does this balloon stay intact? It’s got everything to do with our angle of attack.
Latex, the stretchy material most balloons are made of, is a polymer. Polymers are made of macromolecules, or long chains of repeated small parts. When a balloon inflates, the long molecule chains in its surface stretch out & make room for the air collecting inside.
The balloon isn’t stretched equally in all directions, though. It experiences less tension in two places: the knot at the bottom, and the point directly opposite the knot. You can usually see this point as a dark spot on the top of the balloon. These areas of least stress are ideal targets if we want to stretch the latex out even more…by stabbing it with a skewer, for instance!
Once the surface has been punctured, the polymer stretches tight around the skewer, keeping the air trapped inside the balloon. We coated our skewer with dish soap to make it more slippery and to help seal the gap between skewer and latex.
It’s important to be gentle during the stabbing process– stretching the polymer too much will cause those long molecule chains to tear, popping the balloon! It also helps to twist the skewer slowly as you break each surface (remember to aim for the dark spot at the top of the balloon on your second puncture). A careful touch, a little patience, and, you, too, can have a balloon kebab!
Electricity is one element of physics that we encounter on a daily basis. It powers our televisions and our computers and keeps the lights on at home. Magnets are something we think of as less common, only using them when we need to navigate using a compass or stick something to our fridge. But electricity and magnetism are really just two pieces of the same thing! Let’s shed some light on this idea.
We can see some examples of this relationship using the induction coil. There are really two parts, so lets tackle them one at a time. First, whenever electricity runs through a wire, it creates a magnetic field. If the wire is in a circle, the magnetic field will be the strongest through the middle. By stacking up several loops of wire to make a coil, then we can create an electromagnet.
Diagram of an electromagnet. Credit P. Wormer.
Electromagnet at AstroCamp. Pressing the button sends electricity through the wire solenoid which is coiled around a nail to create a magnetic field.
Not only can electricity be used to create a magnet, but magnetism can be used to create electricity. When a conductor, like a metal wire, feels a changing magnetic field, an electric current is created. We can even use this electricity to power a lightbulb! This process is called induction, and it is the basic principle by which electricity is generated in almost all power plants.
Strong neodymium magnets are rotated inside a coil of copper wire, producing a current. The needle moves back and forth, indicating the the current produced in this way is alternating, or AC current.
Combining both of these ideas, we can now see why the small metal ring hovers. Turning on electricity through the coil of wire creates a magnetic field that is felt by the metal ring. Then, through the process of induction, electricity is created in the ring. The ring is now an electromagnet with electricity running through it! The magnetic field from the ring and from the coil are pointed in opposite directions, so they repel, causing the ring to hover in midair. By submerging the ring in liquid nitrogen, we can lower its resistance and increase the electric current. A stronger current creates a stronger electromagnet and the ring shoots up to the ceiling!
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!