# Paperclip Science!

Today is National Paperclip Day! Yes, even those simple bits of bent wire have their very own day. Being a science camp, we decided to celebrate in the only way that made sense: Paperclip science!

Lets start with a simple question. How can you tell if something will float? The most common and simple answer is density. Density measures how heavy something for a certain volume of it. It can be a little tricky to think about, so to make it simple, consider a two liter soda bottle. If we fill it with water, it will weigh two kilograms (about 4.4 pounds). Any substance that would make the bottle heavier than that will sink, and anything lighter will float. Paperclips are made of steel wire. If we filled the bottle with steel, it would weight a little north of 15 kilograms (or just over 34 pounds!). Paperclips should not float!

These two metal spheres have the same mass, but very different volumes, resulting in very different densities. The larger one is hollow.

But we see them floating at the top of the water when carefully placed. As Eric mentioned in the video, this has to do with surface tension. We talked a fair amount about surface tension in our Teacher Appreciation Day post. For a more in depth discussion of this, check out that post here. In short, water molecules hold onto each other tightly. Its what pulls water into droplets, allows you to slightly overfill a glass of water, or pile drops of water on a penny.

Water on a penny. The last drop is just too much for the surface tension to hold.

When the paperclip is carefully placed on the water, the surface tension bends and cradles it. The paperclip is still made out of steel, so it still should sink if you think about its density. However, there is another way to think about buoyancy. It’s called Archimedes’ Principle and has to do with displacement.

If you have a full bathtub, and then you get in it, the water will spill over the rim. This is displacement. When something goes into the water, it moves this water out of the way. The water doesn’t compress. Instead, it is lifted up. When you put something in the water, the force pushing up on it is the weight of the water that it pushed out of the way.

The less dense ball, when pushed underwater, displaces a mass of water greater than its own. Since buoyancy is stronger than gravity for this object, it is launched out into the air!

This fits perfectly with the density explanation as well. If we put the bottle of steel in the water from before, it will displace 2 kilograms of water, but weigh over 15 kilograms! As it weighs much more than the water it is displacing, it will sink.

However, the surface tension changes things for the paperclip. Above is a picture from beneath the floating paper clips. This is also how water striders walk on the water. The water bends, and displaces more water than the paperclip normally would.

A paper clip weighs about half of a gram. With the surface tension bending the water, it displaces more than half of a gram of water, allowing the paperclip to float, delicately, on the surface.

Soap is a surfactant. It greatly reduces the surface tension of the water. With the surface Note that another object like a ping pong ball would still float. It is held up by the fact that it is less dense than water, and does not require the aid of surface tension.

This same phenomenon is what causes this to happen when soap is added to some milk and food coloring!

# Electricity & Magnetism Belong Together

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!

# 2015 Space Tech Expo: Space Exploration

The 2015 Space Tech Expo is in full swing! Over 2000 people are attending the conference and festivities in Long Beach this week, including some of the biggest players in the industry like SpaceX and Boeing. With such a focus on the newest technology and ideas for space flight, we thought this would be a great time to take a look back at this exciting year in space exploration!

The past year has been an especially exciting time for those of us always looking skywards!

NASA had its first test launch of the long-awaited Orion Spacecraft back in December. The world watched as Orion sat on the launch pad, and then watched again as its launch was rescheduled due to a faulty valve. The second launch went off without a hitch and NASA scientists are still going through the data after the successful test flight.

Orion launches into the early morning sky on December 5th. Credit: NASA, Kennedy Space Center

There were also a couple of notable firsts. The ESA succeeded in the incredibly delicate task of landing Philae on the surface of a comet. As the Rosetta spacecraft stayed in orbit around the comet, it unearthed new information about their makeup and origins.

Rosetta takes a selfie with Comet 67P and its Philae lander somewhere below. Credit ESA, Philae, Rosetta, CIVA

The first orbit of a dwarf planet when NASA’s Dawn spacecraft settled in above Ceres. In doing so, it revealed the now-famous mysterious white spots.

Rotation of Ceres from pictures taken by the Dawn spacecraft showing the mysterious white spots. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

SpaceX continued to really push the limits, including their attempt to reuse the Falcon 9 rocket. This was closely followed by its “Rapid Unscheduled Disassembly”….perhaps one of the best phrases for such an event ever used.

The Falcon 9 recovery ends in a “Rapid Unscheduled Disassembly”. Photos from Elon Musk

2015 has more to offer as well, with New Horizons, the fastest spacecraft ever launched, closing in on Pluto having already sent back the best pictures of it to date! New Horizons will continue its mission, making the first ever flyby of Pluto on July 14 before heading further into the Kuiper Belt in search of a new target.

This animation of Pluto from New Horizons shows a light region that might indicate the presence of an ice cap! The animation makes it look as though Pluto stays still, but in reality it wobbles due to its relatively large moon. Credit NASA, New Horizons

We also had the start of the Year in Space. Astronaut Scott Kelly went back to the ISS for his second stint. This time, he will stay for a whole year. His twin brother, Mark Kelly who was also an astronaut, will remain on the ground. After this year, they will be examined back on Earth to try to get a better idea of how space affects the human body.

Astronauts Terry Virtz and Scott Kelly show off their space suits in the Quest Airlock. Credit NASA TV

The Orion Spacecraft and Scott Kelly’s year in space have generated a lot of excitement about Mars in people from AstroCamp staff and students, to President Obama himself. Whatever happens, the future of spaceflight isn’t set in stone. It’s set among the stars.

# What does Liquid Nitrogen do to Balloons

Liquid Nitrogen is a cryogenic liquid. It seems exotic because its extremely low temperatures cause it to affect things differently than we see in everyday life. To understand it a bit better, lets look at where it comes from.

Nitrogen is a very common element. It makes up about 78% of the atmosphere, so you are quite literally surrounded by it constantly. This can be surprising to some people, as we know that people need to breath oxygen. However, of every breath you take, only about one fifth of it is actually oxygen!

Image from M7 Science.

Liquid nitrogen is simply this same gas, but cooled down until it became a liquid. There are three primary states of matter: Solid, liquid, and gas. Most elements can be found at any of these three states of matter. Which state of matter you find depends on two things: pressure and temperature. In chemistry, we have something called a phase diagram to help us visualize this idea. Lets look at one that is a bit more familiar. Here is the phase diagram for water.

Image from Pearson Education.

This diagram contains a huge amount of information. First of all, at sea level, we experience 1 atm of pressure. At that pressure, water freezes at 0℃ or 32℉ and boils at 100℃ or 212℉ as expected. However, large changes in pressure can change that a bunch! One unique characteristic of water is that at higher pressure, the freezing temperature actually gets lower. This is very important, as it means that our oceans and lakes will freeze on the tops and not at the bottoms! Another interesting feature of the diagram is the triple point. At this exact temperature and pressure, all three phases of matter can exist equally.

The phrase diagram for nitrogen is similar, except the temperatures are very different! At the same pressure of 1 atm, nitrogen freezes at -210℃ or -346℉ and boils at -196℃ or -320℉!

Image from CHEMIX Chemistry Software.

As the balloons are dipped into the bowl of liquid nitrogen, they shrink rapidly. We have seen this before in several of our other blogs, where we talk about how temperature and volume are related. To summarize, when gases get colder, they take up less space. However, this is more dramatic than we have seen before!

This is because we are taking a balloon filled with atmospheric air and subjecting them to liquid nitrogen. The nitrogen in the air gets cold enough that it starts to turn into a liquid! Liquids take up far less space than gases because the molecules are closer together. For nitrogen at room temperature, the same amount of gas takes up 694 times as much space as a liquid! Want another example? Here we pour hot water into liquid nitrogen. As the nitrogen instantly evaporates, it pushes around the water vapour to fill almost the entire room!

# Fire Suction

Physics allows us to manipulate the world around us in fun and creative ways.  The fire suction experiment is a good example.  We want to grab a penny from a plate that is covered in water, but we don’t want to touch the water.  At our disposal we have an empty soda can, some matches, and a glass.  What do we do? Well, we light the matches and put them inside of the coke can (cut in half) and cover the water and can with the glass as seen in the video.  As if by magic the water gets sucked up into the glass leaving the penny exposed to the air!  Walah!

So what was actually happening?  We are taking advantage of a principle called the Ideal Gas Law: PV=nRT.  Since the volume of the glass won’t change, the important part for this experiment is that the pressure exerted by a gas is proportional to its temperature.  So as the gas gets hotter it exerts more pressure.  The glass separates our system so that there are two different sources of air pressing on the water covering the penny: the air inside the glass and the air outside the glass. The match heats up the air on the inside.

As the temperature of the air inside the glass drops, the pressure it exerts on the water also decreases.  That decrease in pressure causes the water outside the glass to get pushed into the glass by the air outside the glass.  Eventually the system balances with all of the water sucked into the glass.  That’s pretty cool!

# DIY Project on Teacher Appreciation Day!

What a great holiday! Teachers are incredibly important in a child’s life, and their influence doesn’t stop when the school year ends. Their experiences, ideas, and memories will stay with their students for years to come. In addition, most kids decide whether or not they are interested in science or math at a very young age. As these STEM fields become more important than ever, this becomes a real issue.

At AstroCamp, we are science enthusiasts. This probably comes from the fact that we get to see awesome science demonstrations and experiment with amazing materials every day. However, we understand that this isn’t the background of every teacher. Trying to teach something that you aren’t familiar with can be a very tall task. As such, we wanted to give back with an easy but incredibly cool DIY science project!

One of the reasons this is a great demonstration is that the materials are easy to procure. All you need is a plate, dish soap, food coloring, whole milk, and a cotton swab.

To perform the demonstration, simply pour some milk into the plate. Add food coloring drops on top. It doesn’t really matter where you put the food coloring so feel free to get creative!

Once you are satisfied with your food coloring artistry, add a bit of soap to the cotton swab. Simply dip it into the milk. Enjoy!

Wow! One of the other great things about this demonstration is that it can be used to teach more than one thing! For younger kids, you can add certain colors and use it as an experiment where the goal is to learn about how colors mix together.

For more advanced or older students, it can be used to illustrate quite a bit. It all starts with something called “surface tension”. Water molecules (H2O) are highly polar, meaning one side is positively charged, while the other is more negative. These opposite charges attract. The oxygen parts of one molecule will be attracted to the hydrogen portions of nearby water molecules creating a tightly attracted tangled mess.

Inside the water, this pull occurs in all directions. At the surface, the water is pulled down, as it is not attracted to the air in the same way. This attraction causes the surface to hold together. With small amounts of water, this is what causes droplets to form. However, if some other molecules get in the way of this attraction, the surface tension will change.

Milk is mostly water with some dissolved fat molecules and other stuff in it. Soap molecules have two parts: A polar head that interacts nicely with water, and a hydrocarbon tail that doesn’t get along with water at all! When the soap is introduced, it quickly begins to surround the fat molecules in the milk. This disrupts the surface tension in the center of the plate, leading to the rest of the surface being pulled away by the remaining surface tension further from the soap.

It all happens very quickly, but can be re-initiated by adding another bit of soap! After enough soap is added, all of the fat will be surrounded by soap, and the surface tension will be irreparably changed. At this point, adding soap won’t do anything further.

At this point, this fun activity is a great teaching tool and demonstration. To make the activity more inquisitive and experimental, feel free to try doing it with other liquids (water, half-and-half, different kinds of milk, juice, coffee etc.) or other kinds of soap and see how the results change!

### 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!