The atomic bomb

We did a whole unit on Nuclear Energy a few years ago. It was one of our favorite units! You can find all the posts about that unit aggregated here.

The Nuclear Museum in Albuquerque.

Hydrogen bombs vs. atom bombs

Great article on why we dropped the atomic bomb. And some more good resources on the same subject. Definitely worth watching and teaching. I found a real lack of good information on this subject elsewhere, as most children's books and other modern resources have a sort of glib "we all know better now" sensibility on the subject.

Abe and I LOVED this book, Bomb, by one of our favorite authors, Steve Sheinkin. There is SO MUCH intrigue and so many behind-the-scenes details I had never before heard about. It reads like a mystery novel.

I can also recommend this book (for adults and older children), Hiroshima Diary, which is a journal written by a doctor in Hiroshima in the weeks immediately following the Hiroshima bomb. It is fascinating, sad, and surprisingly good-humored as well. The author seems like a pretty amazing man.

Videos about Nuclear Energy

There's a lot of good information about nuclear energy to be had. Along with a lot of bad information, naturally. :) Here are some of my favorite resources:

This a good video explaining pressurized water reactors

We thought this movie was great---a really good introduction to nuclear energy, how it works, and its benefits as a source of power. It's about an hour long and the older boys and I were fascinated the whole time. The Heritage Foundation does good work.

This is a pretty good list of links related to nuclear energy and its history

This is a good video by Ontario Power Generation. The Canadian accents are a bonus. The video briefly overviews nuclear, hydro, and coal-powered plants, so it's a good look at how similarly they work.

Another look at an Ontario power plant.

I think we watched all of these videos. We especially liked the one about mining, but they're all good. We (Abe and Seb and I, especially, though Ky watched some too) just couldn't get enough of this stuff. One afternoon after we watched the Heritage Foundation video, we started watching through all these other links, and before we knew it, five hours had passed and Sam was driving in from work and there was no dinner ready. We just love this type of thing.

Here's a tour of San Onofre power plant. We hope to visit this one someday, since I think it's relatively near my brother in California. I read that it's not running right now, though. Hopefully it will be again soon.

Here's a lady talking about her career as a nuclear reactors engineer for the Navy. It sounds fun.

This is really cool. It shows how they recycle spent nuclear fuel.

Some reactors under construction in Georgia.

We wish we could find out more about the current status of this project.

Nuclear Fusion

So many of our books couldn't get over the idea that Fusion! is the Energy! of the Future!  I found their reasoning pretty simplistic and I'm not so convinced (nor am I sure the massive expenditures will pay off), but, regardless, it sure is interesting to learn about! I found what I think is the best activity EVER to demonstrate fusion. It's described here, but basically, when you apply heat and pressure to mini-marshmallows, they will "fuse" together. It's like magic! We loved it.

It's also helpful to show a chart of electromagnetic energy when you talk about the energy fusion releases; this is from here

We had our periodic tables handy, and we would choose two elements and get marshmallows to represent the number of protons in each one. For the simplest example, you take two atoms of hydrogen (one proton each; so you take one marshmallow in each hand)---add heat and pressure (roll them together between your palms very fast)---and they fuse to form a new element, Helium (2 protons)! At the same time they release lots of energy (represented by the lentils).

This happens at very high temperatures, in a plasma in fact, so the electrons are free and we don't even have to worry about them. :) If you really rub your hands together hard, the marshmallows fuse so completely, they look like one marshmallow again! Which is cool, but it's more helpful to see the individual "protons," so we backed off and didn't rub so hard. Still: magic!

I let the children create as many elements through fusion as they wished, as long as they told me which elements they started with, and their atomic numbers, and then figured out which new elements they were creating (also based on atomic number). They had so much fun, and the fused nuclei were truly amazing. They gained a lot of familiarity with the periodic table as well.

As we learned more about fusion we became curious about the transuranic elements: that is, the elements PAST Uranium on the Periodic Table that are man-made. How did they make them? None of our books seemed to mention this; they just said they were man-made and didn't occur naturally.

So, we asked Karl (my brother the physicist). Here's what we learned.

(our questions in black; Karl's answers in blue):

Now we have another question: how do they create the transuranic elements, and why is it not fusion when they do so? We read that they can be made in particle accelerators, but we thought that's what what's-her-name--Lise Meitner---was TRYING to do when she discovered fission. And she discovered that bombarding the nuclei DIDN'T add particles, but split the nucleus instead. I know some things are more fissionable (?) than others, like U-235, but they were using U-238 in those original experiments and that still split instead of adding protons.

Fission happens because very few configurations of protons/neutrons are stable.  When you send two nuclei together, they will most likely create an unstable nucleus which will then split into two more-stable elements, not necessarily the two that collided in the first place.  You might get lucky and find that one of the resulting elements is more massive than either target.  

And, even if they do have a way of making the protons "stick" and add themselves to the nucleus, why doesn't that create tons of energy like fusion? And if they can hardly even make Hydrogens fuse, how on earth could they make heavier elements fuse---which seems like it would be harder? 

To get excess energy from fusion, you need to have the mass of the combined nucleus be less that the mass of the separate nuclei by more than the amount of energy it takes to shove them together.  Larger nuclei are harder to shove together, and the mass difference is smaller, so no excess energy.  Yes, they are very hard to get to fuse, it takes huge accelerators.  Think of trying to push the N poles of two magnets together vs. trying to push 100 magnets together. 

The problem with H fusion (Deuterium, actually), is not getting them to fuse (they do it all the time).  The problem is getting it to be self-sustaining and not energy-consuming.  I just read an article by a high school science teacher claiming he had calculated that even D fusion could never be a net energy producer.  I was skeptical given that thousands of scientists clearly think it can be.  (But you might say they have a conflict of interest because they want funding.)  Hmmm. 

I bet it will take 100 years of a fusion generator to make back all the energy spent on fusion so far. 

Karl.

Interesting, eh?

Nuclear Submarines and Nuclear Rocket Propulsion

We were very interested in other uses of nuclear fission technology (besides in power plants). There are two areas in particular we learned about: nuclear submarines and nuclear-powered rockets.

Submarines are now powered by nuclear reactors almost exclusively, we learned, as they allow the subs to stay underwater for such long periods (the fuel doesn't require oxygen as a combustion engine would!) and thus allow great stealth. This site has a great video on the subject; we also had a couple books.

It was funny, a couple weeks later: I was reading the children a book about dolphins, and it said they used high-pitched sounds to bounce off objects to help them navigate, a technique called echolocation. As we'd talked about this before with our Night unit, I asked, "What other animal uses echolocation?" Seb immediately shot his hand in the air and stopped me almost mid-sentence. "Nuclear submarines!" he said. "Oh, and bats." Yes, Sebby thinks nuclear submarines are animals. How sweet. :)

The information we had on nuclear rockets was sketchier. We read about the Orion project, after WWII, which explored the idea of using nuclear bombs to propel rockets. It was eventually scrapped in favor of the Saturn rocket series (chemically propelled) but we kept finding references to the fact that "nuclear technology is also used in rockets today." However, we couldn't find many details about this, even on the NASA site!  Luckily I have a physicist brother that I can turn to. Hooray for Karl! I reproduce our conversation here, not because I think it will be particularly interesting to most, but in case someone who doesn't have a physicist brother is searching for the same information.

Karl's answers appear in blue:

Karl, 

Is there an easy way to explain our current nuclear rocket technology? We learned about the Orion project in the 1950s-70s, which proposed using tiny fission bombs to propel a rocket. After that project was cancelled, we learned, nuclear rocket propulsion was mostly abandoned---but then we read that the Russians have been using nuclear power for their rockets for some time, and that the New Horizons spacecraft also uses nuclear power for some things. But we can't find details. We assume it's not the tiny nuclear bomb thing, and the boys surmised that maybe it was a mini nuclear reactor, like they use in nuclear submarines. Do any rockets use this, and if so, how? (They don't have propellers for the turbines to turn, do they?)

First, I'd never heard of the Orion project.  It sounds dangerous!  I'm not surprised it never came to fruition.

We tried to read about the New Horizon spacecraft, and it talked about radioisotope technology, but very vaguely. Does this mean they AREN'T using a reactor, but instead just using the natural radioactive decay of plutonium to create heat? And then what is the heat used for? And wouldn't that be too slow/weak of a power source to fuel a rocket? There was a bunch of stuff on the NASA site about how safe! and not scary! this technology is, but not much about how it actually worked.

Every use of radioisotopes harnesses their heat.  In a fission reactor, you get a lot of Pu and a lot of heat, and you superheat steam with it and drive a turbine which turns an electric generator.  You are correct, there are no turbines on spacecraft.

If no steam and no turbines, what is left?  There are thermopiles and thermovoltaics.

Thermopiles are multiple thermocouples in series and parallel to generate the needed voltage and current (Seebeck effect).  An example of a thermopile is in your gas fireplace if you have one.  The little rod poking into your pilot light is a thermopile, and it generates enough electricity to open the gas valve.  Your fireplace will run even with the power out. 

A thermovoltaic works like a photovoltaic (photocell) where the "light" is very long wavelength (IR) light from the hot radioisotope.  These are less common. 

Some spacecraft that use thermopiles: Cassini, New Horizons, Curiosity. 

When we say the spacecraft are powered by these devices, we refer to generating electricity for the on-board systems: communication, navigation, attitude control, etc.  Not propulsion.  They are sent on their way using conventional rocket propulsion.  The entire future trajectory is set in the first few minutes of flight!  It does use small jets of hydrazine for attitude correction. 

The boys also wanted to know, are there any plans to use the "tiny bomb" type of rocket in the future? Or to use a fission reactor, if they aren't already using them?  

No plans that I know of, and I'd be surprised to ever see it. 

Karl.

Next we wondered:

Thank you! Very helpful. We are disappointed there is no nuclear propulsion method. Wouldn't that be able to get us much farther into space, if it could be done?

And Karl answered:

I don't really know how much better that would work.  Propulsion is all about Newton's 2nd law: action, reaction.  The only way you can go forward in space is to send some mass backward.  An explosion sends some mass backward, very fast.  But not all the energy coming from the explosion can be turned into motion.  A more spectacular explosion does not result in any more motion. 

If you want to get the most bang for the buck, so to speak, I believe you want to be gentle.  That is, you want to get the maximum eventual speed for a given amount of propellant since you can only take a finite amount of propellant with you.  I believe the best engine in that sense is the ion engine.  A heavy gas atom is ionized and accelerated through a potential.  As it exits the engine, an electron is added to the ion to make it neutral again, and therefore not attracted back to the spacecraft.  Therefore, the entire mass of the gas atom minus the tiny fraction that is the electron mass is converted into forward momentum. 

It takes years for these to accelerate to an appreciable speed, but they will get us farthest into space because of the efficient use of the propellant.  (To get away from earth's gravity, you do need to do something violent to create enough acceleration at first.) 

Karl.

So! There you have it. Thank you Karl, for a concise explanation of nuclear-powered rockets that anyone can understand! After all, it's not rocket science! (Ha ha! Sorry, I can't help myself. We kept that joke going for several days. We had a book called This is Rocket Science that set us off.)

Here is a bit more information, from the NASA site.

And an interesting video about a small reactor for deep space exploration.

Nuclear Power Plant Model

image from here

Nuclear power plants work almost exactly like hydroelectric power plants, except they use controlled fission to make steam which turns the turbines, rather than using gravity and water to turn the turbines. Once we understood the nuclear reactor, it was easy to visualize because we'd already talked so much about hydroelectric power during our water unit.

To help us visualize the fuel rods (small pellets of enriched uranium, arranged in a row inside metal rods), we put black beans into straws to make our own "fuel rods."

They bundle up bunches of these rods to make a fuel assembly for the reactor. In between them is a moderator (a liquid that slows the free neutrons down, such as "heavy water" [large percentage of deuterium in the Hydrogen]) and some control rods that can be raised or lowered to absorb neutrons and slow the chain reaction as needed. It's really such an ingenious method; I don't know how they figured it out!

Anyway, once we had our control rods made, the older boys would not rest until we had finished modeling the entire power plant, including the reactor. It was really fun finding things around the house that we thought were good representations of the various parts.

I don't know if you can read the labels very well (maybe if you click to enlarge this) but at left we have the containment dome, holding fuel rods (where fission occurs) and control rods. The superheated water generated here rises into the steam tank, where it turns that water into steam. The steam goes out through a steam line and turns the turbine, which in turn spins the generator (magnets + wire to create electrical current). The electricity then goes through a transformer (represented here by a Transformer, ha ha; the boys thought they were SO funny) and from there into the power lines where it lights up the flashlight at the end of the paper. Meanwhile, the steam goes into the cooling towers (vases) and much of it escapes out the top as water vapor. As it cools it flows back to the condenser, which turns the rest of it back into cool water so it can re-enter the steam tank to be heated again. There's also a reservoir of cool water nearby to add more water to the system as needed.

Pretty cool, eh? The boys were so proud of themselves. They wanted to keep their model around forever, but it was on the floor, so, with Junie and Daisy walking around, it had a very short life. (Half-life?) :)

Nuclear Power Plant worksheet

I think you should be able to print these out if you download the images. (Originally from here.) Just make sure you print them both at the same scale so the labels are the right size for the blank spaces. (Oh, and the answers are here.)

This was a fun worksheet for the children to fill out. Because we'd spent so much time talking about it, and had read so many books showing similar diagrams, even Malachi was able to tell me which label went where, once I read him what they said.

Daisy enjoyed doing hers too, as you can see:

Seb is in his element here. He LOVES diagrams and if I don't provide him with any, he draws his own. 

The Atomic Bomb and WWII

My explanation of the famous equation. That's what it all comes down to, right? Anything x Very Big = also Very Big? :)

Every single day of this unit, the boys were saying, "Is TODAY the atomic bomb? Is TODAY the atomic bomb?" Finally we got to it. Having lived in Los Alamos while my dad worked at the lab there, I've always had a special interest in the Manhattan Project and the people who worked on it. My mom has lots of good books on the subject from our time in Los Alamos---just the portraits of their daily lives there (even the wives and children who were there with their physicist husbands) are really fascinating. I have pictures of me at the Trinity site when I was 3, but I don't remember it. I think I have some trinitite too. (I used to think my Uncle Hale worked on the Manhattan Project, but he didn't. He helped develop Radar, though.)

Anyway, I don't know what's more interesting, the history or the science! We had a unit on the Holocaust earlier this year, but we didn't cover the war with Japan at all, so we needed a brief recap of the timeline of World War II and an overview of Pearl Harbor, etc. This site has some interesting before and after pictures of Hiroshima and Nagasaki (before and after the bombs were dropped). I wouldn't get too far into this page with kids as there are some very disturbing pictures of people and their injuries; we stayed away from those. (They are behind a link at the bottom of the page, though, so you shouldn't run into them by accident.) Whatever your feelings on the bomb (another reason I wouldn't get too far into that site), it's very sobering to see the pictures and think about the destruction caused. 

I liked the story of Lise Meitner, one of the discoverers of fission and a very interesting woman. I've always liked Marie Curie but I'd never even heard of Lise Meitner before. There's an element named after her now (Meitnerium)! (I liked this whole book, though it wasn't all pertinent to this unit: serendipitous discoveries are so cool!)

Of course we also listened to Manhattan Project, one of the best Rush songs ever. :) This one made a deep impression on me as a teenager and I've liked it ever since.

There are videos all over online that show atomic bomb explosions. The boys loved those. They are pretty awe-inspiring! This video was one of the most interesting, about the largest thermonuclear bomb ever detonated.

Chain reactions; Enriching Uranium

When we started talking about fission, we needed to understand chain reactions, and of course the obvious example is with dominoes. We tried several different configurations and experimented with putting rulers in to simulate control rods.

Here's how I demonstrated the enrichment process for Uranium. This was all new to me, although naturally I'd heard of "enriched Uranium." Here's a good explanation of how the Uranium centrifuge works. By the way, there were some really terrible books about nuclear power at the library. I feel that Atoms and Molecules by Molly Aloian deserves special dishonorable mention for its reversal of U-235 and U-238 (it repeatedly referred to U-235 as the most abundant isotope, and U-238 as the one you need for fission----which is exactly WRONG), spelling errors (e.g. "canon" for "cannon"), and general hysterical tone (YOU DECIDE: "Is radioactive waste going to KILL US ALL?"). I really hate pseudo-scientific books like that. Nuclear energy seems to be a hot subject for it, unfortunately. But generally, I could get what information we needed from the books and leave out the other stuff, so it was okay.

Anyway, here's how it works with getting Uranium ready for fission.

First, the Uranium ore is in deposits all over the world. The yellow beads represent U-235, the rarer isotope, and the wood beads are U-238, the most abundant natural source. (U-235 is disproportionately represented here, actually. I think it's only 1-2% of the world's uranium.)

They mine the ore and gather it. (Um, this is a simplified explanation of the process. :))

Then they add chemicals to make it into a gas. The U-235 is sliiiiightly lighter, but gravity alone won't separate the two isotopes. They have to use a strong centrifugal force, which they do by spinning the gas in a centrifuge. The lighter U-235 tends to stay in the middle while the heavier 238 spins to the outer edges. You actually have to do this thousands of times before the separation becomes pronounced enough, so the gas goes from centrifuge to centrifuge, becoming more concentrated in U-235 each time.

Finally you have a solution that is mostly (or, MORE than before) composed of U-235. This is the enriched uranium----the pile of yellow beads. And you also have depleted Uranium, the U-238 left over. Both have their uses, but the enriched Uranium is what's used for nuclear power plants and for nuclear weapons.

And this video from The Onion is just for your enjoyment. :)

Radiology Field Trip

When I called the Hospital to schedule a tour, I asked if we could specifically see the radiology department, as that was what we were studying. I also told the lady the ages of the kids, but evidently she didn't remember them, because when we got there, the radiologist's face kind of fell and she said, "Oh, I wish someone had TOLD me they'd be so young!" So it was sad, because they ARE young, but people underestimate them, because they are also smart. And we'd been learning about this stuff already, so they had a lot of background and would have been ready to learn probably a lot more in-depth than she imagined. I tried saying, "It's okay, just try us, we'll stop you if we don't understand!"---but some people just don't think kids are capable of much, I guess.

So, it was a great field trip, and we loved what we did get to see, but we felt like it was way more dumbed-down than it needed to be. The lady talked in this high, kind of babyish voice and said things like "And THIS is the X-RAY machine! It's like a big . . . CAMERA! Like your mom and dad's CAMERA that takes cute pictures of you! Only pictures of your INSIDES!" I could see the kids kind of tapping their feet and thinking, "Okay, when are we going to get to the ionizing radiation?"

We did get to see a bunch of interesting x-ray pictures showing swallowed objects and nails that had gone through people's feet and so forth, and everyone liked that, despite heavy moralizing from the radiologist ("And so THAT'S why you should always let your mommy put you in your CARSEAT!"). A little moralizing never hurt anyone where broken bones are concerned, I suppose---the children were duly sobered and impressed. :)

One funny moment came when Malachi raised his hand and asked why the cords and tubing above the machine were so large. The lady began to explain ("You see, there's something called ELECTRICITY in there, like a plug in the wall---you know there are plugs for your TV in the wall, and you must NEVER stick your finger in because you might get a SHOCK? . . . ") and then Malachi understood what she was trying to say and kind of cut her off: "Oh, it's extra insulated because of the large current. Okay." She seemed rather taken aback, but at that point the tour was nearly over so it didn't do any good. :)

Naturally, in the days that followed, Sebby made several of his own x-rays (each one a cautionary tale) showing horribly fractured arms and legs, as well as people who had swallowed saws, staplers and open safety pins.

Radioactivity

Radioactivity is such an interesting phenomenon. We loved learning more about it. I highly recommend this book, not for reading aloud (it's way too long and on more of a high-school level) but just for a fascinating (and unbiased) overview of the subject. I learned so much from reading this.

Here's a nice little animation to demonstrate half-life and radioactive decay.

This is a really interesting chart showing radiation dosages for various things. The children thought this was the most hilarious sentence in the world:

"Using a cell phone* does not produce ionizing radiation and does not cause cancer. (*Unless it's a bananaphone)"

Bananas, you see, contain potassium and thus give a small dose of radiation (more than a cell phone, evidently). Now the children are obsessed with holding bananas to their ears and saying, "Hello?" They think it is THE FUNNIEST JOKE.

No, actually, I take that back. They think this video contains the funniest joke: when Robert Krampf says, "Does radioactivity turn you into some horrible monster?" and then suddenly appears wearing a big bunny suit. We love The Happy Scientist! This is a good, concise explanation of radioactivity and the cloud chamber looks like a really cool project to try. We didn't attempt it this time because it seemed like it would be so much better with a radioactive source, and we didn't have one. :) But it's really amazing to see the "trails" left by alpha and beta radiation!

Along with naturally occurring radiation, we learned about the uses of radiation in medicine. We had a field trip to the Radiology department of the hospital planned, so in preparation for that we learned how X-ray machines and CT Scans work, and about radiation therapy for cancer. We also really enjoyed this picture gallery of interesting x-ray pictures. The photographer took x-ray photos of unusual things like jet airplanes and football players in uniform. So cool!

Here is a video about CT scanners
And here's one about radiation therapy for prostate cancer

Paper plate atom models

I thought of various ways we could build models of the atom, and finally decided on this one as the simplest. I saw some instructions for doing this with M&Ms, but as you were supposed to be gluing them to the plate, this promised to be either wasteful or futile. So we used beads. The main point of making a model, in my mind, was to cement the concept of which subatomic particles go where, and which ones determine the properties of an element---and this accomplishes that sufficiently.

I told the children they could choose any element to model. I helped Malachi and Daisy, of course (it was a good counting exercise for both of them---Malachi chose Gold, so he had to go up to 118 for the neutrons) and Abe and Seb were able to do this on their own.

Here's a simple, printable periodic table if you need one. I remember when I was in 6th or 7th grade, my dad brought home a periodic table for me that was colored and detailed (with the full mass numbers and such), printed on heavy paper. I was so proud of it and felt like I was SO lucky compared to everyone else in class that had to make do with their ugly Xerox copies. I kept it in my binder for years and always felt special when I brought it out during classes. It was such a simple little thing, I'm not sure why I loved it so much, but I think I just loved that my dad gave it to me. Anyway! This one isn't as nice, but it will do. :)

Abe wanted to do the lightest and the heaviest naturally-occurring elements.

Sebby wanted his to be shaped "right" :)

Isotopes (or, as we called them, eggotopes)

Regular Hydrogen with its isotopes, deuterium and tritium

I've always thought isotopes were a little tricky to visualize. But the concept is critical to understanding radioactivity and the uranium enrichment process! Luckily I found this great idea from a junior high science teacher online. You use colored eggs to represent elements. Each isotope of an element is in the same color. Inside, you make a nucleus with beads, showing the number of protons and neutrons in each isotope. The model leaves out electrons altogether, as they aren't relevant here.

(One thing the children were SO interested in was half-life---specifically, how some elements have such a short half-life that they decay almost immediately. Protactinium, for example, would have been totally gone from the earth only hours after it first appeared. They loved that idea, for some reason.)

We really liked doing this, and we also used the eggs later on in the unit for reference. I had really small plastic eggs, so we only did some of the lighter elements, but it would have been fun to make an egg for U-235 and U-238 if we'd had one big enough to hold that many beads! I just looked up a list of common isotopes (some radioactive, some not) such as Carbon-14 and of course the three isotopes of Hydrogen. (That knowledge would be necessary for learning about nuclear fusion later!)

Here's a simple online explanation of isotopes.

Also, stringing beads is fun!

Sulfur-32 and Sulfur-35 (radioactive)

Nuclear Energy Unit Lesson Plan

We decided to plan a nuclear energy unit after we went to the Museum of Nuclear Science and History in Albuquerque a few months ago. There was so much information at the museum, and the children were curious about it all, but there was too much to really absorb in a few hours. They asked if we could study it in more depth later, and I said we could, though I wasn't really sure how it would go. I wondered if the subject was maybe too complicated for me to cover (as, alas, I'm not a physicist. If only Grandpa were still alive!). But, I forged ahead and checked out a bunch of books from the library about atoms and nuclear energy.

Luckily (as seems to happen every time!), after reading so many books and trying to absorb so many explanations, everything began to make sense and I felt like I would actually be able to teach it! Not on a college level or anything, but well enough. I have wondered if this is perhaps the only post on "Nuclear Energy Homeschool Unit for Children" in the entire world! I certainly couldn't find anything no matter how much I searched online. However, there were some good resources on the individual sections of the unit---some for older students that I could adapt for a younger audience, and some that were a bit advanced but I thought we'd try anyway. The children loved our studies about hydropower, so I knew they'd be able to understand the basic model of a nuclear power plant once we had a good basic understanding of atomic structure and radioactivity.

Okay, that meant starting with atoms. We learned some about atoms and elements in our fireworks unit, so this wasn't totally new. One activity we did was to help answer this question: how do we learn anything about atoms if we can't even see them? I gave each of the children a paper bag, stapled shut, with something inside. They had to figure out what was in there without opening the bag. They could shake their bags, throw them, crumple them, feel them, etc. to determine what was inside. They did pretty well (though only Abe actually guessed his object correctly, I think) and I think it did a good job of conveying how, by doing things to atoms, we can learn about their properties even when we don't see them.

Another thing we did that ended up being really memorable was a demonstration of just how much empty space is inside an atom! I read in one of our books that if the nucleus was the size of a golf ball, the electrons would be rotating around it about 2 miles away! I showed the children the way we usually draw atoms (the nucleus with electrons hovering nearby) and then explained how it was just a convenient representation, but didn't show the actual scale of an atom. I put a golf ball on the table and asked them, "If the protons and neutrons are here, where would the electrons be?" We then got in the car, started the odometer, and drove until we'd gone two miles. Then I stopped the car, told them to remember where the nucleus was, and said, "The electrons would be clear out here!" They were amazed. :)

I usually put up butcher paper on the windows or walls as a place I can draw examples when we're learning about something. These are some of the terms we learned about as we reviewed atomic mass, atomic number, how to read a periodic table, what ions are, etc. We also talked about the four forces in the universe and their relative strengths and influences. All this was good background for what was to come.