Download they aren`t just made of ice. They are made from

Comets are icy objects that orbit the sun. They are
most often found in two areas past the orbit of
Neptune: The first is the Kuiper Belt where Pluto
exists and the second is the more distant Oort
Cloud. There could be billions of comets in the
Kuiper Belt and Oort Cloud.
Occasionally the gravity of the sun or one of the
planets pulls a comet towards the inner solar
system. When this happens, radiation from the sun
causes gasses to evaporate and dust to leak out,
creating the tail we often associate with comets.
Comets actually have two tails - one of dust and the
other of gas.
Comets are often called “dirty snowballs” because
they aren’t just made of ice. They are made from
water ice, gasses like carbon dioxide and ammonia,
silica, and organic materials containing carbon.
Many scientists believe that billions of years ago,
comets brought water and organic materials to
Earth, which eventually paved the way for life to
develop.
Skymobile:
Comet Demonstration
Grade 3
Theme: The Solar System not only has planets and moons, but also a star, dwarf
planets, asteroids and comets. All matter in the solar system is made of solids,
liquids or gasses. Comets have all three states of matter inside of them.
Goals
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Students will be able to identify objects in the solar system as either solids, liquids or gasses
Students will be able to define solids, liquids and gasses
Students will be able to define comets versus meteorites
Students will be able to describe how comets and meteorites affect our planet (and other
planets)
Students will be able to discuss why Pluto is no longer a planet
Materials
Materials
Plastic Bowl
Plastic Bag
Water
Sand
Crushed Coal
Glass Cleaner
Crushed Dry Ice
Plastic Spoons
Gloves
Hammer
Rubber Mallet
Large Spoon
Specifications
Quantity
1
1
N/A
N/A
N/A
N/A
N/A
2
1 Pair
1
1
1
Use
Supplier (if known)
Procedure
1. Start by defining the solar system and asking students to identify objects in the solar system. As
the list is created, the students can see that our solar system has 1 star (the sun), 8 planets
(Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), hundreds of moons,
countless asteroids and comets, and an ever growing list of dwarf planets- Pluto being the most
important. (Pluto is the most important dwarf planet because it was the first defined as such.
When Clyde Tombaugh first discovered Pluto there was debate at the time on whether or not
it should be defined as a planet). During this discussion, define the terms Asteroid Belt, Kuiper
Belt and Oort Cloud. Following this discussion, define how the IAU (International Astronomical
Union) defined what constitutes a planet to help students understand why Pluto is no longer a
planet.
a. A planet orbits the sun (which Pluto does)
b. A planet needs to be spherical in shape (which Pluto is)
c. A planet needs to clear the path of its orbit (which Pluto does not)
2. Once the solar system has been discussed, the focus switches to comets. The difference
between solids, liquids and gasses are introduced by showing the students a piece of water ice,
liquid water, and a piece of dry ice. The dry ice is used to define sublimation – the process of a
solid turning into a gas. You can illustrate this further by placing the dry ice into a cup of water
and letting it sublimate very quickly. Once the students have an understanding of solids, liquids
and gasses, the construction of a comet begins.
- Students will be asked if they know what the states of matter are, which are covered in the
3rd grade standards. We will take suggestions and discuss with the students at each state of
matter given. The students will be asked to knock on their desks for solids, shown a bottle of
water for liquids and instructor will steam up a clear plastic cup by blowing into it to show
gas. They are informed that the cool thing about comets is that they are actually made up of
all three states of matter and this is written up on the board.
3. As the different ingredients are added, certain terms can be defined: Silicate is inside a comet,
and it’s the breakdown of this silicate that causes shooting stars. As the comet orbits nearer and
nearer to the sun, it begins to heat up and sublimate. The tail of the comet that is created can
stretch from its proximity to the sun, all the way to Jupiter. As the Earth orbits the sun, it passes
through the tail, forcing the grain size silicates to pass through the atmosphere. Friction causes
the silicate to flash brightly and creates a meteor. The other ingredients in the comet are
representations of carbon and other ices within the comet. Once the comet is constructed,
point out that most comets are the size of small hills or mountains.
- When silicates are discussed, we ask the children if they are familiar with what silicates are.
They are then asked if they have ever been to the beach and played with sand. The sand is a
type of silica, which is written up on the board for the students to see and repeat out loud.
- Friction is discussed by asking the students to take their hands and placing them together
and then rubbing them back and forth with increased force and speed as they go. This will
be for just a few seconds and then they will be asked to stop this action and describe what
they felt happening with their hands. This is the same that occurs when the Earth travels
into the trail of material left by a comet.
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Carbon-based life forms: We ask the kids if they have ever been to a barbecue and if they
enjoy their hamburgers, hot dogs and meat (the 4th of July is used as an example for a time
when we will b-b-q) and ask what they observe the adults using to cook those items (we are
looking for charcoal to be suggested) and bring out a small charcoal nugget and inform the
kids that the charcoal contains something called carbon and that carbon is something that is
not only found in a comet, but that it is also something that makes up all living life forms,
from you and me to the trees and plants outside and even the dinosaurs!
Gasses: Since the states of matter were written on the board and have been checked off
one at a time as we cover them with the kids, they will be asked if anything is missing from
the ingredients in the comet that we are making. Gas will be pointed out as the missing item
in our bag and we will bring out the window cleaner and point out that, while there are no
windows to clean up on the comet, the window cleaner does contain one type of gas that
can be found inside of a comet, a gas called ammonia!
At each step, the students will be asked to make any observations that they see with the bag
that contains the classroom comet that is being built in front of them. The contents of the
bag will change in color and apparent texture as more and more objects are added, but the
big finale is the completed classroom comet that they will see that is beginning to sublimate
even upon its completion right before their eyes. They are then asked to continue to make
any observations in regards to their comet (which they will be asked to name to make it
more personal to them) and to note what happens to the comet as the day progresses, then
see what they observe the next day when they come back to school. By that time, the
leftovers are only the solid ingredients that we had started out with, the silica and the
carbon.
4. Sample Comet talk – to be used only as reference – instructors will formulate their own talk as
they get more familiar with the information:
Good morning! Today we’re going to talk about our Solar System. Does anybody know what the
Solar System is? (Allow the students a few moments to answer.) That’s right! Our Solar System is the sun
and all the objects that revolve around the sun. Let’s make this easy. I want you to raise your hands and
when I call on you, you will tell me one object in the solar system, and I will list them on the board.
Ready? O.K. Let’s begin. (It doesn’t matter what objects the students list at what time but you want to
make sure that they understand that we have one star (The Sun), 8 planets (Mercury, Venus, Earth,
Mars, Jupiter, Saturn, Uranus and Neptune), 5 dwarf planets (Ceres – which is located in the asteroid
belt – Pluto, Haumea, Makemake, and Eris), approximately 173 moons (Earth – 1 Moon, Mars – 2 moons
Phobos and Deimos, Jupiter – 63 moons (perhaps mention the four large Galilean Moons – Io, Europa,
Ganymede and Callisto – most students get a kick out of learning that Ganymede is the largest moon in
the Solar System and larger than Mercury), Saturn – up to 67 moons (maybe more) – mention Titan as
being the second largest moon in the Solar System and also bigger than Mercury and being the only
moon with an atmosphere, Uranus – 27 moons, Neptune – 13 moons and even dwarf planet Pluto
having 2 moons – Hydra and Nix (Charon is under debate as to whether it is a dwarf planet that shares a
common gravity with Pluto or is one of the moons of Pluto), and millions of asteroids and comets – take
time to take about the two belts – asteroid and Kuiper and the one cloud - Oort) When you define Pluto
as a dwarf planet, you will want to tell them what a dwarf planet is. In simplest terms there are three
rules that define a planet: 1. A planet must be spherical. 2. A planet must revolve around the sun. 3. A
planet must clear the path of its orbit. A dwarf planet cannot be a satellite. Pluto fails the third
requirement and was therefore redefined by the IAU (International Astronomical Union) as a dwarf
planet in 2006.
This is a great list everybody! Now before we go any further we have to talk about the states of
matter. (Take out the three plastic cups and line them up in a row and take out a bottle of water.) Now
this may seem tricky at first, but I know you’ll understand what I’m talking about when we’re through.
Raise your hands if you know something that is solid. (Take some answers). That’s right! Your desk is
solid. Your chair is solid. Your pencil is solid. Your books are solid. Anything that you can hold, sit on or
stand on is solid. Now I’m going to show you something else that is solid. (Take out an ice cube). Does
anybody know what this is in my hand? (Take some answers). That’s right! It’s an ice cube. Now is this
ice cube solid? That’s right! I can hold it therefore it is solid! Now watch this. (Grasp the ice cube firmly
in your hand and let the water drip to the floor). What happens to the ice cube as I hold it in my hand?
(Take some answers). That’s right! It turns into water. Now water is a liquid. I can hold it in my hand but
eventually it runs off. What else is a liquid? (Take some answers). You got it! Juice, soda, milk and gas
that you put in your car are all liquids. Now I’m going to put the piece of ice in one cup to represent
solids. What do you think will happen if I put this cup with ice in it in the Sun? (Take some answers).
That’s right! It will melt into water which is a liquid. So I’m going to pour some liquid into this second
cup. Now… What would happen to the liquid water in this cup if I left it in the sun? (Take some answers).
That’s right! It will turn into gas! When a liquid turns into a gas scientists call it evaporation. (Pick up the
third cup). Now watch this. I’m going to put some gas in this cup. (Blow into the cup until the gas
condenses on the sides). Do you see that? Does anyone know what gas I blew into the cup? That’s right!
Oxygen! Now we’re going to see something really cool! And when I say cool I mean cool! (Put on your
glove and take out a piece of dry ice). See this piece of ice? It’s not turning into liquid as I walk around.
It’s turning into what? (Take some answers) You got it! It’s turning into gas! Does anybody know what
this ice is called? (Take some answers). It’s called dry ice. And the reason why it’s called dry ice is
because it doesn’t turn into liquid. It turns immediately from a solid into a gas. This is called
sublimation. Everybody say that. This ice is also known as carbon dioxide ice and it is really cold. It is 109 degrees below zero! That’s why I have to wear this glove. F I put the ice on my skin it would feel like
it’s burning me but it’s actually freezing the skin so fast I would get what we call frostbite! So we have to
be really careful when we handle this ice.
Now the reason why we talked about solids, liquids and gasses is because everything in the solar
system is made out of one or a combination of these three states of matter. Four of our planets
(Mercury, Venus, Earth and Mars) are solid rock and four are what we call gas giants (Jupiter, Saturn,
Uranus and Neptune). The Sun is a big ball of hydrogen and helium gas that provides the solar system
with light and heat. The asteroids are big balls of rock and iron flying around between the planets Mars
and Jupiter. And comets… well comets are special. Comets are mountain size objects that look like dirty
snowballs. Let me show you a picture. (Take out the picture of the comet and walk around the class
showing the students). Comets are mainly made up of ice but they also have other things inside. Now
the best way to see a comet would be to actually go into space and look at one up close, but we don’t
have time to do that this morning… It would take us 15 years to get close enough to one to study it
correctly. So what could I do to show you a comet? Show you a picture? Well I did that already and it’s
hard to see what’s inside. Bring a comet here? Well, I could do that I guess but it would take a long time
to bring it to your school and they’re so big it would probably crush your classroom. How about I make
you one? Yeah! Well O.K. But I need everybody to stay in their seats because some of the ingredients
can be dangerous.
The first thing we need is a bowl. (Place the bowl on the desk in front of you). The next thing we
need is a plastic bag. (Take out a plastic bag and put it inside the bowl). Then we’re going to pour some
water in the bag. Now is water a solid, liquid or gas? That’s right a liquid. Now remember the comet is a
dirty snowball. So we’re going to put something in this water that would make it dirty. This something is
also what makes a shooting star. You ever heard of a shooting star? That’s right! It’s that flash of light
you sometimes see at night streaking across the sky. So I want you all to close your eyes and when I say
open them I will have a shooting star in my hand. Ready? Close your eyes. (Take one grain of sand out of
the bag and put it in your hand or between your fingers). O.K. Open them! (Walk around the classroom
to show each student the grain of sand). Now you might think I’m crazy telling you that this little grain of
sand creates that big flash of light but I’m telling you the truth. Here’s how it happens. When a comet
gets near the sun it begins to heat up. As it heats up the comet actually sublimates – remember – turns
from a solid into a gas, and begins to grow this long tail. Now these tails can be millions of miles long –
they can actually stretch from where it is by the sun to Jupiter – which is 800, 000, 000 miles away! As
the tail grows these tiny bits of sand fly through space. Now the Earth goes around the sun, and every
once in awhile the Earth will go through a comet’s tail. When the Earth moves through a comet tail all
these tiny grains of sand shoot through the atmosphere of our planet causing the sand to catch on fire.
Now how does that work? Simple! Clap your hands together. Now begin to rub them together slowly.
Now go faster! And faster! And faster! And faster! Now rub them 1000 times per second! Come on you
can do it! All right! You can stop. What happened to your hands? They got hotter. Now if you could rub
them 1000 times per second they would get so hot your hands would burst into flames. That’s what
happens to the grains of sand from the comet. They are moving so fast through the atmosphere – the
blanket of gas that surrounds the planet – that they burst into flame! This is called friction. Have you
ever seen someone or have you ever rubbed two sticks together to make a fire? Well that is also friction.
Now we have to put this sand into the comet. But we’re going to call sand by a different name. We’re
going to call it silica. Can you all say that? All right! (Put a few spoonfuls of sand inside and shake the
bag).
Now I’m going to show you the next thing that goes into our comet. (Take out a piece of coal).
Do you know what this is? That’s right! Coal! Now I don’t want you to think that people are in the comet
barbecuing hot dogs. That would be crazy. But coal is made from carbon. And carbon is inside living
things. Living things like plants. Coal is made from plants that died millions of years ago. Over time
pressure and water changed the plants into this black sedimentary rock. Carbon gets into our universe
when stars explode which is called a supernova. The carbon is flung out into the universe and freezes
with the gas, and liquid and silica that make up the rest of the comet. So we have to put some of this
crushed coal inside. (Put a few spoonfuls of coal inside and shake the bag again).
The next thing in the comet is this stuff. (Pull out a bottle of glass cleaner). Anybody know what
this is? Glass Cleaner! Now I don’t what you to think that there are people cleaning the windows in the
comet… but there is a gas in the glass cleaner that freezes in space. (Spray some glass cleaner). Ever
smell that sharp smell when you spray this stuff. That’s called ammonia. In space ammonia freezes easily
because it’s really cold out there. Here on Earth you can freeze it but if I brought it to your school, I
would probably cause an accident. (Spray a bunch of ammonia in the bag and then shake it up).
All right everybody… when I’m done shaking this I will have a comet. Actually all I have is a
bunch of dirty water. What am I missing? You’re too smart for me. I am missing ice. So here’s what
we’re going to do. I’m going to put some of this dry ice into the comet and then stir it up. Take a look.
(Place a few large spoonfuls of ice into the bag). The last thing I’m going to do is crush the comet into a
ball – I’m basically going to act as gravity. (Gently mold the comet by squeezing the ice together inside
the bag). O.K. Give me a second. (Cut the bag down the side and pull out the comet). And here is our
comet! Let’s give it a name…
Vocabulary
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Asteroid Belt: The region of space between the orbits of Mars and Jupiter in which most
asteroids are located.
Dwarf Planet: Any celestial body within the solar system that is larger than a satellite but
smaller than a planet, and that orbits the sun
Friction: Surface resistance to relative motion, as of a body sliding or rolling
Kuiper Belt: See also cloud a region of the solar system beyond the orbit of Neptune, some 30-1000 astronomical units from the sun, containing up to one thousand million icy planetesimals
or comet nuclei
Meteor: A meteoroid that has entered the earth's atmosphere. A transient fiery streak in the
sky produced by a meteoroid passing through the earth's atmosphere; a shooting star or bolide.
Meteor Shower: The profusion of meteors observed when the earth passes through a meteor
swarm.
Oort Cloud: A region of the system far beyond the orbit of Pluto in which billions of comets
move in nearly circular orbits unless one is pulled into a highly eccentric elliptical orbit by a
passing star.
Plasma: A highly ionized gas containing an approximately equal number of positive ions and
electrons.
Silicate: Any of the largest group of mineral compounds, as quartz, beryl, garnet, feldspar, mica,
and various kinds of clay, consisting of SiO 2 or SiO 4 groupings and one or more metallic ions,
with some forms containing hydrogen. Silicates constitute well over 90 percent of the rockforming minerals of the earth's crust.
Solar System: The system containing the sun and the bodies held in its gravitational field,
including the planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), the
dwarf planets (Eris, Pluto, and Ceres), the asteroids, and comets
Sublimation: To transform directly from the solid to the gaseous state or from the gaseous to
the solid state without becoming a liquid.
Additional Information