"The atoms of our bodies are traceable to stars that manufactured them in their cores and exploded these enriched ingredients across our galaxy, billions of years ago. For this reason, we are biologically connected to every other living thing in the world. We are chemically connected to all molecules on Earth. And we are atomically connected to all atoms in the universe. We are not figuratively, but literally stardust.” Neil deGrasse Tyson
Introduction
Obviously, particle physics need to be dumbbed down (a lot), but it's the basis for all chemistry, so it's worth getting them seeing the world in these terms. Kids are naturally curious about "the smallest thing ever" as my 5-year old puts it.
Lesson plan
[Take something that is rippable or dividable like a piece of paper or bread-alternatively, show space in between fingers and keep dividing it in half--space is more relevant for Planck length, elementary particles for sizes of massed objects]. Let’s rip this in half once, then let’s rip it in half again. If my fingers were able to take a hold of it, do you think we could keep ripping this in half forever?Or is there a limit to how small something can go?
There is a limit to how small something can go called the Planck length. We don't know much about that really small, small world. Maybe you'll be the scientist that discovers what it's like down there. If something is one Planck length, then one end of it will always be in the same place as the other end. That is the smallest that you can get.
For us to be able to see a planck length though, we would need a microscope [particle accelerator] the size of our entire galaxy!
Much bigger than a Planck length are little pieces that cannot be broken down to any smaller pieces. These are called "elementary particles." As far as we know, you can't break these things into even smaller pieces, they are just there.
There are 17 of these that we know of, and we think there is an 18th and have even given it a name (graviton) but haven't found it yet; maybe you'll be the one that discovers it. Light is made up of one called photons. Another one is called a quark, and three quarks together make what is called a neutron or a proton. Another elementary particle called an electron combines with the neutrons and protons to make what is called an atom.
Atoms are mostly empty space though. If the atom was a stadium, the protons and neutrons together would be a bowling ball in the middle of the stadium, and the electrons would be flies buzzing about at the edge of the stadium. However, they're buzzing around so fast that it’s like a solid wall of flies that
don’t let anybody in. The flies can also be two places at once and jump
from one place to another.
Atoms usually stick together in groups called molecules.
[Draw graph of different particle structures with arrows, show them how big one is compared to the other, although briefly mention Bose-Einstein condensate as a special atom that is so big you can see it with a microscope]
If you were to tear a piece of paper in half, the smallest piece of paper that you would have while it was still a piece of paper would be a molecule. If you were to keep tearing a piece of aluminum foil in half, the smallest piece of foil you could have and have it still be aluminum would be an atom. If you were to keep tearing it, it would stop being like paper/aluminum foil.
An atom is the smallest piece of something that you can have and it is still like that thing.
In
the past, the Ancient Greeks thought that everything was made out of
air, fire, dirt and rocks, and water. Later, scientists decided that
some of the dirt and rocks were different, and thought that everything
was made out of 33 different things (they started calling them
elements). One scientist found out that there was a pattern in these
different elements and he predicted that there were more elements. There are 118 different kinds of atoms that we know about. Everything in this world is made up of 118 different types of stuff, not just the four the ancient Greeks thought.
Everything in the universe (almost) on this one sheet of paper. Really neat. Basic building blocks. They think that there may be other types in the darkest parts of space, but we don't know a lot about them.
They are different because of how many protons they have. [Show them the periodic table]. Hydrogen, which is what stars and our sun are made out of, has only one proton. Every proton wants one electron, so it has one proton and one electron. They also have neutrons, but the number of neutrons doesn't matter for changing the element, but it can make the element a little different, we call atoms of an element with a different number of neutrons an isotope, an isotope is like the flavor of an atom.
Protons are what determines how heavy something is. Can of aluminum is not very heavy, but a can of gold would be [kids like talking about gold], this is because gold atoms have more protons. This is why balloons filled with helium float. [Point to periodic table]. The air around us mostly nitrogen, oxygen, and carbon with their protons, but helium has only two protons, so it's lighter. [Note-not necessary at this point to introduce technical terms like atomic number, goal is to get them to grasp it conceptually and be interested in it at this stage].
We have these 118 things, but you usually only see maybe 10 throughout the day. Many of them would kill you if you touched them, many would explode and burn you, so they only play with them in laboratories.
These 118 things can be solids, liquids, or gasses though. They are a solid if the atoms go really slow and are close together [use arms to show motion as well as images], when they get really fast, they melt, and when they get really, really fast, they turn into gas. But some things turn into gas faster. Some things are naturally gas at room temperature like the air we breathe, somethings are naturally solid at room temperature.
When something gets so cold that the atoms stop completely, this is called absolute zero, and it is the coldest that anything can be. It is negative 460 degrees. Scientists have gotten very, very close to this, but they haven't quite reached it.
These different 118 things combine into molecules, but some of them combine with others better. For example, the atoms in this column [point to halogen column] combine a lot with the atoms in this column [point to alkali metals column]. This is because electrons are negatively charged and protons are positively charged, so each atom wants a certain number of electrons depending on how many protons they have. The ones in this column [Halogen] want one more electron, while the ones in this column [Alkali metals] have one electron too many that they're trying to get rid of, so they get together, and when they exchange that electron they stick together and become a molecule. This is where salt comes from (sodium chloride).
This sometimes makes it difficult to find certain pure elements in the earth, since some of them have already stuck to other elements.
For example, aluminum usually sticks to other atoms. Because of this, it was very, very rare. Even rarer and more expensive than gold! The Washington monument had an aluminum top because they wanted it to be made out of the most expensive metal ever. Now we throw aluminum cans away after we're done. Can you imagine throwing a gold can away? We do this because a scientist found out how to separate the aluminum atoms from the other atoms it had stuck to.
(By the way, diamonds and gold are precious because they are so rare; all the gold ever mined would only make a cube about 60 feet high, wide, and long, but the rarest element that earth makes is astatine, there's only one ounce of it in the entire earth!)
The first element they did this with was phosphorous. It was an accident, since the scientist was trying to create the "philosopher's stone," a stone they had heard about in legend that could turn lead into gold. He didn't invent that, but he discovered phosphorous.
Another atom that likes to stick to other elements is iridium. Because it likes to stick to iron, most iridium is stuck to iron, and most iron on earth is in the middle of the earth. However, there's a lot of iridium in comets that don't have iron. Scientists found a layer in iridium in the part of the earth that was at the surface during the time of the dinosaurs, so since iridium is found in comets, and since the dirt during the time of the dinosaurs was covered in iridium, a lot of scientists think that a big comet hit the earth and that that's what killed the dinosaurs.
Some elements have enough electrons though, it's like they are full and don't want anymore, but don't want to give anymore away. These are the "noble gasses," and they rarely ever combine with other elements. On element called mercury only likes to stick to itself, so if you spill it on the floor it forms into little balls, since it only wants to be by mercury.
Carbon wants four electrons, that's a lot! Since it wants so many it can combine with a lot of other atoms. It can also combine with carbon, that's one reason why we are made out of carbon, it can combine to make all sorts of animals and other living things, and it's how carbon can make both diamonds and us. Carbon names end in ly, scientists made it that way so that you know what kind of an element something is just by looking at the name. If you remember that then you've learned thousands of new words.
Silicon wants four atoms too, but it's so big and heavy that it's hard for it to form so many different shapes.
Hydrogen is what most of the stuff in the universe is. After the big bang, almost everything was hydrogen. This hydrogen formed stars that started to burn this hydrogen and turn it into helium, the next heaviest element on the scale. Stars burn hydrogen for billions of years. After all the hydrogen is burned up, the stars start to burn helium for a couple hundred million years. The helium is turned into an even heavier element--lithium and berylium [show them the periodic table in sequence]. This is turned into carbon, the star burns carbon for a couple hundred thousand years and creates neon, it burns neon and turns it into oxygen for a few years, then it burns the oxygen and turns it into silicon for a few more years. Finally, in about one day the silicon is burned and turned into iron.
After the star is heavy with iron, it stops burning because it takes more energy to create heavier elements [continue gesturing at periodic table] than it gets back in burning them. So how do these heavier elements get made originally all the way from hydrogen? Well, a lot of stars explode at the end of their lives, and when this happen a lot of energy is shot into these atoms and they combine in all sorts of ways to form heavier and heavier elements.
This is important because you are made out of carbon. Your body was originally created in the middle of a star! And any metal you see that is heavier than iron like gold was created in an exploding star! Without this heavy, rocky stuff formed in stars we couldn't have solid ground and planets to walk on. After the stars explode, the rocks formed in the star cool down and become solid, then float around space until they all come together by gravity and form a planet.
Sometimes when there's a lot of pressure, these elements behave in really weird ways. Jupiter is made up of an ocean of black liquid metal hydrogen that would crawl up walls all by itself if it was on earth. This ocean is so deep you could fit about ten earths in it stacked on top of each other.
We've only been able to make small dots of it in labs here. Jupiter's sky is orange and creme, not blue like ours, and it has glow in the dark rain. Imagine glow in the dark rain falling into a pool of black metal with an orange sky and that's what the surface of Jupiter looks like.
Really heavy atoms are used for weapons. Because they are so heavy, they can tear into other metals like paper. Armies put uranium in bullets and tank shells.
The
first 94 elements occur naturally; the remaining 24, americium to
ununoctium (95–118, point to chart) are only made in laboratories. All of the elements heavier than einsteinium (element 99) have only been made in such small amounts that you need microscopes to see them. Some of them haven't even had pictures taken of them.
If you were to make a brick out of these elements, it would immediately kill you. Because they are so big they are unstable; when atoms are unstable and electrons and protons go flying around, it can cause heat damage to people and kill them, so it's probably good that they've only made them in small amounts in a lab.
Scientists are always trying to make brand new elements. According to the table, there are still some that they might be able to make. The newest element was discovered a few years ago [point to it and explain]. The Russians and Americans are in a race to see who can create the most elements. Some people think that the largest element that is ever possible to make is element 137, which they have called Fenymanium, but it's still a long ways to go before we get there, since we've only made it to element 118!
Activities
Do Single simple chemical reaction and explain in terms of electrons, such as baking soda and vinegar. http://scienceline.ucsb.edu/getkey.php?key=4147
Future Lesson Development
I haven't taken the time to really understand the systematic interrelations in the periodic table of elements. This will be important when the kids are older.
Brian Green's books have the most straightforward explanations of the weird aspects of quantum mechanics I've encountered. Usually when most people try to explain how weird quantum mechanics are they utterly fail ("light is a particle AND a wave!"--so it's a particle/wave hybrid, I don't get it...) Next time we come around to this lesson I'll probably introduce some of these concepts.
I have yet to find a popular press book on elementary particles (Higgs boson, etc.) that is amateur understandable. Maybe the topic is beyond amatuerizing but I'm open to any suggestions for some that I may have missed.
In the future I want to do more hands-on work with free online molecule simulators and visualizers: http://www.nyu.edu/pages/mathmol/txtbk2/topic9.htm
Reading for Parents
The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements
What If? Serious Scientific Answers to Absurd Hypothetical Question: This book has a fun chapter on what it would be like to construct a wall made out of a brick of each element.
Web Resources
https://en.m.wikipedia.org/wiki/Ununennium
https://www.ptable.com
Video Resources
"Hunting the Elements"--decent documentary, available on youtube
Bill Nye Matter, Periodic Table, Atom episodes
Magic Schoolbus atom episode
Kahn academy periodic table clip
Material Resources
Poster of periodic table
