Messy Monday: Science Projects for Kids, Teachers, and Parent Helpers

December 27, 2012| cometary| 0 Comment | 4:44 am

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Hands-On Science

Welcome to the first official posting under this new category. In these installments, I’ll be sharing science projects developed over many years while serving as The Science Mom at my local elementary school and in a community after-school program. When my friend Jean Southland and I first started the in-class projects, the teacher invited us in on Mondays, to create a fun activity for that worst-of-days to students, the First Day of the School Week. We fooled around with ideas to give this extra science class a name and settled on Jean’s simple and inviting “Messy Monday”. Since then, Jean moved on to wider-scale education duties, from teaching to administration, and she is now head of a local charter school. In the meantime, I continued with developing classroom-scale science projects and coaching a small robotics team.

When the youngest of my kids finally moved on from elementary school and my geek needs were being satisfied by playing with robots, I felt twinges of guilt that I was leaving the next round of students in the lurch. The most-frequent comments I heard when running science project sessions could be summarized as: “I could never do that”. Sometimes it was the teacher, in which case she/he would mean “I can’t spare the time to figure out supply lists, shop for stuff, sort out materials, and test procedures.” Other times, it was another parent, in which case the meaning was either “I could do that, if only someone would explain what it’s supposed to mean” or “I understand the science, but someone needs to give me a checklist to follow.” And in these times, potential cost is always a concern, as most supplemental projects—from field trips to science experiments—end up being funded by parents or from teachers’ own pockets.

In these episodes, I’ll be having a stab at meeting both sets of needs. With any luck, the end result will be a book of “recipes” for science projects with enough information provided for teachers to slot into their curricula in order to satisfy the science standards they must meet, with clear supply lists to distribute to classroom-helper parents, and with step-by-step instructions for completing projects that any interested parent or teacher will be able to not only follow but build upon to suit their own audiences. While (like every other blog in the Known Universe) the ultimate result is to be a book of projects that a teacher or parent helper could have at hand, in the short term, there will be first, these erratic blog entries and second, a series of leaflet-style e-docs in a more readable/printable form, to be available from the usual e-book suppliers. Think of the blog entries as the beta version, the leaflets as the Basic Edition release, and the eventual book as the Portmanteau Edition, with updates, extensions, and add-on packs as needed.

To open the subject, I’ll be delivering a flurry of quick posts to get things started, but then will back off to a more regular pace. The goal is to deliver one project-worth of information in no more than two weeks.

Every Messy Monday project guide has four key components:

A set of notes for project leaders, sketching the key elements of the project and the science topic it is meant to address
A detailed supply list, structured to make it simple to purchase supplies for either a one-shot demonstration or for a classroom-sized group activity.
A set of instructions for working through the project with students, including commentary to help cope with common classroom-management issues, questions that are likely to arise, and issues to keep in mind from safety to fairness.
A rough estimate of the cost to run the project.

So, let’s get started with a truly cometary project…

You might also like to read:

Chasing CometsChasing Comets

As a re-entry activity, let’s fall right into the project which inspired the overarching theme for this so-called blog: cometary tails. That is, in this instance, we’ll be “studying” the behavior of the tails of actual comets falling along their orbits about a star. But of course, this is a “Messy Monday” project, so it involves running, arguing, and playing with scissors (not all at the same time).

So far, the only star whose comets we’ve observed have been those of our own Sun, but as our star is not particularly unusual, it’s likely that comets ply their trade throughout the cosmos. We’ll not be delving too deeply into astrophysics, instead we’ll be building fun models of comets and playing games which illustrate the apparent motion of a typical comet’s tail. If you’re running this project as part of a school science program, you can double-count the activity as a P.E. session, as the central game involves more than a bit of running, though not likely moving as fast as a comet.

Just as a reminder, what I want to give you in these “Messy Monday” project descriptions is 1) enough background on the science that you’ll be prepared for questions and have resources to draw on if your own curiosity is triggered, 2) a play-by-play description of running the project with a group, recognizing that your time and resources are limited and your participants will vary in both interest and prior knowledge, and 3) a shopping list detailed enough to help you minimize your costs as well the time you have to spend assembling supplies.

Shoemaker-Levy panoramic (courtesy NASA-NSSDC)

Fragments of Comet Shoemaker-Levy heading for Jupiter (courtesy NASA-NSSDC)

So, What Do You Want to Know?

For thousands of years, humans have wondered at the strange visitations of comets.

Natural philosophers of the middle ages studying comets.

In our time, people now understand that comets are not harbingers of doom or annunciations of the births of kings but fellow travelers in our solar system, icy bodies wheeling in towards the sun and shedding a fraction of their substance as they approach the sun. However, a key aspect of the comet’s tail remains counterintuitive to us earthbound air-dwelling creatures. The tail of a running horse flows behind her as she gallops, so we naturally expect that the tail of comet simply flies behind it as it plunges along its course. But a comet’s behavior plays tricks with such expectations.

Where do comets come from? The Solar System is a big place, but for most of us, the territory ends with Pluto, the Object Formerly Known as The Ninth Planet.

Great_Comet_of_1577 by Georgium Jacobum von Datschitz public domain

The Great Comet of 1577

However, if you’re a fan of Cosmos (either Carl Sagan’s or Neil DeGrasse Tyson’s version) or if your school is lucky enough to have new textbooks, then you’ll know about the Oort Cloud , that sphere of orbiting material from which most comets emerge. Do you realize how much farther out this region is? On a scale of one inch per 100,000 miles, in which the orbit of Pluto would be one mile across, the distance from the Sun to the Oort Cloud would be the length of the state of California. It’s even been hypothesized that the Oort clouds of neighboring stars may physically interact, exchanging comets.

The Oort cloud is a long way out, but it’s still a part of the Solar System, because the objects there are still subject to the Sun’s gravity. Occasionally, a piece of this clutter is jostled from its orbit and begins the long fall towards the sun. Depending on the path it takes as it zooms around the sun, the comet may slingshot out of the solar system entirely or it may settle into a new orbit, returning to loop around the sun on a regular schedule. For instance, Comet Halley returns every 86 years. The last time round, it actually came in ’86–1986 that is. I was lucky enough to visit New Zealand that year, so I can confirm that Comet Halley was extremely unspectacular that year–only just barely visible. Fortunately, New Zealand itself is spectacular every single day of any given year. NASA was more successful, having a noticeable advantage in telescope access.

Babylonian Astronomers Wrote Down Their Observations of Halley in BCE 164

Comet Halley’s Appearance Dooms King Harold in 1066

Comet Halley in 1910

Comet Halley in 1986 (Courtesy of NASA)

But why do comets even have tails? We don’t see shiny tails glowing in the wakes of our planets. Well, it all has to do with the change in environmental conditions as the comet moves towards the Sun. Comets are composed of water ice, frozen gases, rocky matter, and even traces of organic compounds. As this frozen jumble approaches the sun, it warms up enough that the various ices in the outer layers of the comet become gaseous—water vapor, ammonia, carbon dioxide. These gases bubble and boil into a misty cloud, so the comet will have an atmosphere of sorts, called the coma, for the duration of its passage through the inner Solar System. The gas expulsions may even shoot out of the comet’s rocky layers like jets, causing the comet itself to tumble as it falls along its inward path. At the same time, very small-scale “dust” particles are swept from the cometary nucleus. This is not the heavily-organic dust we find under our furniture here on Earth (if you really want to know what’s in household dust don’t use “Google images”; stick to text searches or just ask your friendly neighborhood allergist). What we mean is that the particle size—a few microns—is extremely fine, about the same size as the particles in cigarette smoke.

We get our fabulous cometary tail once these newly-ejected gases and dust of the coma approach the sun just a bit closer, enough that the various solar emissions can have their ways with the comet’s atmosphere. First, there is sunlight itself, which acts in several ways to provide us with the visual spectacle of the comet’s tail.

The simplest role of sunlight is to shine on the cloud of dust ejected from the nucleus. That’s the main tail we see. But that still doesn’t explain why the dust forms a tail at all: the secret is that light, as electromagnetic radiation, actually exerts pressure on objects, and with tiny objects like cometary dust this radiation pressure force is enough to fan that material out from the core. Plus, there is a cool bonus “secret”: that most comets actually have two tails—one formed by the gases and one formed by the dust. The ultraviolet radiation in sunlight blasts the gas particles, stripping away electrons, and so creating a mass of ionized gas, which fluoresces (mostly blue) in sunlight. Then those glowing blue ions are blasted in a straight line away from the sun by the solar wind, a stream of high-energy particles hurtling at supersonic speeds through the solar system. The solar wind is a wonderfully intricate system in its own right, but for our purposes here it is most important to convey that, like earthly winds, it consists of particles moving at high speeds and that its direction is away from the Sun.

The result of all these combined forces is that a complex, continuously shifting cloud of gases and dust streams out from a comet during its time in the inner solar system and that tail—or, rather, pair of tails—points away from the sun, even when the comet is on its way back out to its origin. (If you’re a die-hard comet enthusiast, you’ll know that the dust tail does curve inward a bit, as the small particles of dust battle with the solar forces, striving to curl into their own individual orbits about the sun, but from our earthly perspective, the outward forces have the upper hand.)

In the next installment, we’ll get down to the nitty-gritty of building our own comet models and playing a game of As the Comet Tail Flies.

Oh, yeah, and I’m not making things up about radiation pressure. Consider the prospects for spaceflight under the power of light!

The Japanese IKAROS spaceprobe in flight (artist’s depiction by Andrzej Mirecki).

Chasing Comets: Notes for Project Leaders #2Chasing Comets: Notes for Project Leaders #2

OK, we’re back for part 2. Remember that our goal is to impart an intuitive, long-term understanding of how comet tails work. I’ll give you an observation worksheet that students can use during the Comet Running game, but if time or attention-spans are too short for a worksheet, dispense with that element in favor of learning through movement and Socratic dialogue. (What? You think an engineer wouldn’t have read the Greek philosophers?)

If you have time and enough outdoor space for the “Game” version of this simulation, move right along to “Stage 2” now. The promise of a chance to make their own models is what will entice the students back to the classroom. Otherwise, save the great outdoor model for another time or place and move directly to “Stage 3,” building the individual models.

Stage 2: The Game

That’s One Big Comet

This is an outdoor game, and it works to best advantage with a nice BIG comet model. Four five-yard lengths of white fabric streamers attached to a single badminton shuttlecock (“birdie”) make our Comet Chase model. A playground ball or a soccer ball (around 8” in diameter) stands for the sun. Sort the participants into groups of no more than five and no fewer than three, and move to the great outdoors. A grassy area is safest, because this game involves some complicated running; if you’re stuck with pavement, tone down the running to “jogging” and allow a little extra time.

Start by laying out the ground rules for the game. First, each group will get to play every role. There are three parts: being the sun, being the comet, and being observers back on Earth. Remind everyone of your local rules for behavior outside. It’s harder to listen to instructions out in the sunshine and fresh air!

Take a moment to review the lesson so far. Place the model Sun on the ground, at least ten yards away. Ask an adult helper or one of the students to stand about halfway between the class and the Sun and to hold the head of the comet

Large Comet Head With Coma

while you extend the tail’s long white streamers. This model is much more evocative of the scale of a real comet, which has a tail tremendously longer than the diameter of its coma, or head—but it’s still not a scale model. Allow for some oohs and aahs, but move on to your query: which direction should the comet’s tail point? Don’t move yet; both you and your helper just stand in place.

Large Comet: Incoming or Outbound?

Don’t be concerned if it takes more than one answer to get the right one! Some may still want to know which way your comet is moving. But in a few moments, you should achieve the consensus that the tail should point towards the class and away from the sun.

Now, add the movement and ask everyone to call out which way for you to move. Ask your helper to start walking (slowly, please!) towards the sun and then to loop around the sun. You will need to move quickly to keep the comet’s tail pointing away from the sun. In fact, even if your helper cooperates by walking slowly, you will need to break into a run! As you run, if the students aren’t already hollering directions to you, tel them to keep reminding you which way to point the tail: away from the Sun!

Pause partway and while you catch your breath you can demo a technique for helping to align the tail while in motion. With your outside hand, hold the streamers. With your inside hand, point at the Sun. The tail-runners should always find that pointing at the Sun also means pointing at the comet’s head.

Now, it is finally the students’ turn. Run as many iterations as necessary to ensure that each group does each job at least once. For instance, for a class of 20, allow time to run the game at least four times.

The Comet Group: The comet group needs one Head and up to four Tail-Runners. Name the comet after the person who’s serving as the Head. Comets are always named according to the last name of the comet’s discoverer. So if you have Robin Williams as the comet’s head, then this will be Comet Williams. Getting the comet named after him/her may compensate for the fact that the “head” only gets to walk slowly around the sun.

Meanwhile, the tail-runners get to hold the ends of the tail streamers and run to keep the comet’s head between themselves and the Sun. In the normal course, the “tail” group will tend to lag a little and spread out, but that actually serves to more-accurately represent the shape of the dust tail. If you’re working with a two-tails group, designate one especially determined runner to represent the ion tail by taking one ribbon and maintaining a straight line from the ribbon end through the comet head to the sun.

The Sun Group: The sun group stands in the middle of your running space. One or two group members hold the model sun overhead. This makes it easier for the Comet group to see if they have successfully aligned the comet head and the sun. If the tail-runners stray out of line, members of the sun group need to to shout out “Got you! Got you!” or “Solar Wind Coming!” to warn them that the solar forces are blasting the tail.

The Astronomer Group: The people who are not part of the sun-comet demonstration still have a critical role. They are not just watching other people play the game, but they are tracking the shape of the comet’s tail as it passes around the sun, as observers on Earth. Depending on their perspective at each point in the comet’s orbit, the tail will appear longer or shorter. For example, if the comet is roughly between Earth and the Sun, the tail may look short, because it is stretched towards us. If you have time for writing, ask the Observers to sketch the comet as they see it. (See the handout.) In an average class, each student will get to observe the comet at least twice, which is very helpful for catching the unexpected views.

When every group has had a chance to play every role, take a few minutes to review one more time. As a comet is orbiting around the sun, which way does its tail point? By now, everyone should be willing to state that the tail always points away from the sun.

Still, you may still have a few hold-outs who are not quite sure this can be true. If you are lucky and it’s a sunny day, you have a hole card to play. Invite the students to each imagine that they are comets. “Guess what? You can see exactly where your tail would be. Who can point at it? Where’s your tail, Comet Human?”

If you are not saved by the insight of a student who’s totally absorbed the lesson, it is OK to resort to hints. “Everyone has one. It’s easy to see. Yes, you can see your comet tail! Where is it? Which way does a comet’s tail point? Right: away from the sun. Where’s the sun right now? What do you have that’s pointing away from the sun? It’s not bright and shiny like a comet’s tail. It’s dark, because there are no sunbeams there.

“Yes! Your shadow is your comet tail. It points away from the sun, always, no matter what direction you run.”

Stage 3: The Reward

Finally, everyone needs a model comet of their own to take home and show off and share with family members everything about how comet tails work. This is not an art project; it’s an opportunity to review and experiment individually. If some students are fussy about carefully arranging their streamers to make a colorful pattern, that is all right, but the point is to assemble a working model.

Each participant needs 24 feet of curling ribbon and a birdie (remember what I told you earlier about calling it by its proper name—be prepared for lots of giggling and teasing if you insist on that) . Cut the ribbon into eight lengths of roughly 3 feet. It is perfectly all right—and in fact more realistic—if the streamers come out various lengths. And depending on the students’ social skills, it is also all right for them to exchange colors once the cutting is done. (There are always some who prefer to discover a multi-color comet and others who prefer monotone.)

Once each student has six streamers, have them tie one end of each streamer to the head of the birdie.

Detail–Attaching Ribbon For Comet Tail

Your meticulous planners will distribute them evenly around the netting; others will be clumped randomly. Either is fine. Every comet is unique and most are quite non-uniform.

Be real. This project is not done when it the comets have been only built. Everyone needs a chance to try them out. They will, of course, want to toss them around the classroom; if this is not acceptable, make some provision for them to try out that technique outdoors. More scientific, of course, as time permits, is to allow the participants to take turns trying out their comets in the pretend “solar wind” of the classroom fan. As long as they willing and able to mind safety rules about working around a fan, by all means have everyone try out the tail position approaching, passing, and retreating from the Fan Sun. But don’t get all hot under the collar if other comets are flying through the room while you monitor the fan users. Just imagine you’re in the Oort Cloud and you’ll be OK.

Up next: Supplies You Need and Resources You Can Use

A Cluster of Comets, Incoming & Outbound

Cooking With Kuiper: The Instruction SetCooking With Kuiper: The Instruction Set

(update: 2/18/2015)

Time to build a comet!

If you have adult or older-student assistants, ask them to take charge of crowd control; that is, keeping the audience from crowding around the demonstration. Everyone will get to see the comet! Spare a minute for a brief lecture on the hazards of dry ice. You may have participants who know that dry ice can “burn”, but not all will understand that idea at first. However, no one wants to get hurt. Mention that you will be protecting your hands with gloves and your eyes with safety goggles (or safety-rated eyeglasses).

Supplies for Comet Making (Just Add a Cooler-Full of Dry Ice)

Supplies for Comet Making (Keep your cooler-full of dry ice in a safe spot.)

Participation opportunities include: helping move the materials and equipment to a mess-tolerant location, measuring ingredients, and smashing dry ice. The trauma of allotting slots to help out is one important reason to try the exercise at least twice. (Crowd-control tip: sometimes it helps to announce “I’ll only choose helpers from those who do not raise hands and call out to volunteer.”) As a first step, take one of your plastic bags and cut it open along one side, then use it to line your mixing bowl. Take 2 other bags and put one inside the other to make a double-thickness bag.

In the first stage, your chosen helpers will take turns measuring all the “safe” ingredients into the bag-lined mixing bowl. Working with the dry ice needs closer control, so keep your supply of CO2 off to one side for now. As you introduce each ingredient, explain why it’s being included. You can use the short explanations provided here as a starting point, adding your own facts or curriculum tie-ins, but remember to keep it brief or you’ll lose your audience’s attention.

Let’s start with water: most comets are composed primarily of water ice. During the early formation of the solar system, the planets were bombarded by comets—so some of the water you will use in this experiment may have actually originated in the Kuiper Belt! (For a popular-science overview, check out this article from Time Magazine.) Your helper will add 2 cups of water.

Next, add sand or gravel: most comets incorporate at least some rocky material. Have your helpers measure out about 2 Tablespoon (TB) of grit.

Next, you’ll add ammonia: real comets typically contain NH3, the active ingredient in this cleaning solution. (Regrettably, few, if any, comets show up to help when it’s time to clean house.) If you’re using a squirt bottle to store the solution, your helper just needs to add one “squirt” of ammonia solution. Otherwise, your helper should measure in 1 Tablespoon.

A Dirty Soup of Rocks, Water, and Organics

A Dirty Soup of Rocks, Water, Ammonia, and Organics

And, for our last step before major excitement sets in, stir in a touch of ice-cream topping: these contain organic molecules, which are a normal component of comets. The organic molecules in real comets are not this delicious–they include hydrogen cyanide and formaldehyde–but comets often contain complex and interesting compounds such as amino acids. Researchers at NASA’s Ames Research Center have shown that amino acids from comets striking Earth long ago during the Solar System’s early eons would not only survive impact but would form even more important compounds for life under the heat of impact. So it may be that we are here to enjoy ice cream (and sugary toppings) thanks to ancient comets. Let your helper squirt in one squeeze-worth (it will be about a tablespoon).

Now, finally, it is time to add the dry ice. Comets contain significant quantities of frozen gases, especially carbon dioxide, which just happens to be the gas that we call “dry ice” when frozen. This stage of your demonstration is a two-step process. First, you will put on safety goggles and work gloves and use the hammer to tap off about 2 pounds of dry ice (1/4 to 1/3 of your supply). Place the chunks into the doubled plastic bag and twist the opening closed. Then, and only then, one lucky volunteer will be asked to don a set of goggles and, once protected, may proceed to smash the contained dry ice with the hammer.

Crushing Dry Ice with Flat Side of Hammer

Have your crusher use a two-handed grip (this helps deflect the temptation to also handle the bag of dry ice and also limits the range of motion, protecting bystanders from the crusher’s swing) and turn the hammer sideways, to smash with a broader surface area.

Once that stage is completed, ask the crusher to rejoin the group. Make sure that the wooden stirring spoon is at hand and that you are still wearing your work gloves and goggles. Then open the bag and quickly scoop out roughly two cups of crumbled dry ice.

2 Cups of Ice-Cold CO2

Give the mixture a stir and then swiftly add the dry ice, stirring vigorously. There will be some dramatic vaporization of CO2 and in moments the dry ice will freeze the water solution to a slushy slurry. Quickly wrap the plastic bag around your slushy mass and—keeping those gloves on—form the contents into a snowball, using firm pressure to shape the contents.

Comet’s In the Bag

You will feel the mass harden as you form your iceball. At that point, it is time to unwrap the comet and reveal it to your onlookers. You will have something that looks surprisingly like the common description of a comet—“a dirty snowball”. You may even want to use your snowball-making skills to firm up the comet a bit once you remove it from the bag–remember to keep your gloves on!

Firming Up the Comet

Your finished comet

Set the comet aside on a cold-safe surface, in a location where the eventual water-ice-melt will not damage anything. The comet will continue to outgas CO2 vapor. If you are working outdoors, any breeze will push this plume into a fair imitation of a comet’s tail.

Gases (CO2) immediately begin to sublime from the comet’s surface

Your experiment team will undoubtedly want to repeat this process. A typical group of students will demand about four comets. After 2 or 3 builds, it will be time to set up fresh plastic bags for mixing and crushing. If the group is larger, find ways for students to share participation tasks. For instance, two students can take turns as dry-ice crusher, two can each measure one cup of water into the mix, and so on. As you proceed, instead of repeating the descriptive information yourself, invite the students to call out more of what they remember about the components represent.

Here’s one small starter comet, let’s call this one “Dirty Little Snowball”

These model comets will last a long time, up to a few hours depending on their size and the conditions. You can explain that the comets which get our attention are much larger–Comet Halley is estimated to be about the size of Manhattan Island–and between visits to the inner Solar System, they orbit back to where it is too cold for water, ammonia, or CO2 to be anything other than solids. By no means do you need to make any effort to create spherical, smooth comets. In fact, as you create successive comets, allow them to be different, irregular, and, well, messy. Here are a few samples from a few of my comet-making sessions:

That's one frosty, rocky, comet: "Before"

That’s one rocky comet, frosted with ice crystals of H2O and CO2

That's one slimy, partly-dissociated comet

Here’s a comet with conspicuous dark patches

That’s one tall, frosty, cone-shaped comet

If your schedule permits, allow some time to pass and return to look at the comets after they have lost more material, as if you are checking in on a comet as it approaches the sun and some of its ice has been drawn off under the combined forces of the sun’s radiation and the solar wind…forming the comet’s tail.

Holey Comet, Batman!