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Crystals for Early Childhood Classes
Name: Adrienne
Status: educator
Grade: Pre-K - K
Location: FL
Country: USA
Date: Winter 2011-2012
Question:
Hello, I am looking for a class science fair project that I can do with my young children. I leaning toward forming crystals...frost or salt crystals or something to that effect. Here in Florida..we will not have snow to look at..but we could have frost and January may be the best month to see it. Our project is due at the end of the month, but I would like to create the perfect environment for frost to form. I do not know how to form the question to where the kids can get see a significant change. I am thinking different surfaces or humidity levels or different locations of town. Could you please give me an idea of something that would be a good questions and how to test it? I hate to say this but I have the young ones, 4 and 5 year olds. So, we really do not have a set science curriculum, but we will be talking about weather, snow etc. I am preschool teacher who is in a religious school. During the science fair, we all do a science fair project. I wanted to choose something that is relevant to their world during the event. I would like for them to be able to see what frost looks like or a crystal made from cold air. I just do not know how to do this in Florida without a guaranteed freeze date.
My back-up idea was experimenting on the absorption of water into different foods or chemical make ups. We watched a gummy bear take in a lot of water the other day and the kids really liked it. I found an experiment on line that shows you how to make crystals with Epsom salt. I thought it would be neat to do that but also teach with them about frost vs. dew...
Replies:
Adrienne -
I think your interest in sharing these things is very encouraging.
I have lots of vague ideas, that probably need some work to make practical.
I may do some later, but at the moment all I can do is talk.
I think it is a fine theme for young children
to show that almost any volatile stuff goes from warm to cold.
That includes:
- water that can evaporate into the air,
- crystals that can dissolve into clear water.
- almost any liquid in an evacuated sealed container (a heat-pipe)
A secondary lesson is to be aware:
is this a closed system or open system?
- if it is closed, volatile stuff plays nice games of preferring the coldest spot in the room.
- if it is open, the volatile stuff can simply go away completely.
And if the world outside is half-full of it, (like water vapor)
sometimes it chooses to come in, adding new stuff to your partly-open container.
My arch-typical setup for this is an emptied drinking-water bottle
laying in a half-cylinder metal cradle, which is split in two at the midpoint of the bottle.
The idea is for the two metal blocks to have different temperatures,
one hotter, one colder, each controlling the temperature of it's end of the bottle.
It helps viewing if the cradle only surrounds the bottle for the bottom 180 degrees.
The cradle needs to conform to the bottle fairly well
to encourage good heat flow for faster demonstrations.
The horizontal gap between the two cradle-pieces could be adjusted:
as little as 1mm if you are eager to see a few cubic millimeters transport in minutes,
to most of the length of the bottle, perhaps for ammonium di-hydrogen phosphate crystals in water,
regrowing big crystals over weeks.
I have left out how you make one end-block hotter and one colder, steadily for a long time.
Many ways and it depends on what you have available.
Those 2-inch square thermoelectric elements, with a proper current supply,
and a heat sink behind each element or the element sandwiched between the halves,
would be the slickest way, but probably too expensive.
Often one end can be simply left at room temperature,
and heat or cold added to the other one.
An electric heater or sunlight on one (black) end would be cheaper ways.
If you buy and try one of those big crystal-growing kits,
ammonium di-hydrogen phosphate is what they use.
It is pretty non-toxic and is one of the fastest-growing substances.
The bottle is nicely cylindrical and clear,
and you can keep it capped and re-grow the crystals in it almost forever.
Evacuating a container can make evaporation/condensation transport of water much faster.
But I think it needs to be a fairly good vacuum,
down to less than a tenth of the vapor pressure of the volatile stuff.
And the container will need to be strong enough to hold up to full vacuum.
It might be possible to cap a 1" to 3"-diameter acrylic or polycarbonate tube for this kind of thing.
Do not know if I will ever get to try this.
One of those thermoelectric elements mounted on a fat metal slab
can make a little dew in only a minute or two.
Flip the switch, the top surface gets cold in seconds, then collects water one way or another.
Hopefully it is cold enough to collect water as frost instead of as dew or ice.
It might help to put a clear cover over it so water vapor gets to it only slowly
and so that air convection and fast condensation can't warm it up as much as usual.
I would probably make the cover by cutting off the bottom end of a drinking water bottle.
It is possible that making frost would require two stages of thermoelectric elements.
I imagine that this much hardware is less likely to be obtainable,
but so you understand about it, I will describe.
It consists of a shallow pyramid-like stack:
bottom layer being four of them in a square arrangement,
then a metal plate to join their tops together,
and in the middle of that plate is a fifth element alone.
The top of that gets almost twice as cold as one-stage alone could get.
Each element is a heat-pump. Electric current pulls heat into one face and pushes it out the opposing face.
That current also makes new heat of its own, unfortunately.
It takes about four elements to efficiently pump away the new heat
generated by the strongest electric current that the fifth element can use properly.
That is why the ratio is 4:1. And why three stages are virtually never used.
In any thermo-electric assembly,
it helps to have the edges sealed with silicone glue or foam
so water doesn't condense in the hollow spaces inside the square elements.
Another thing that comes to mind:
in the lab we often see snow growing from the air
on any metal pipe which has been chilled with liquid nitrogen.
Our company has a couple of big LN2 tanks that always have snow and/or ice on them somewhere.
If you could get a big jug of LN2, not too well insulated,
and cork it with a metal tube coming out,
the tube would grow snow on it in your classroom, capturing water from the air.
chilled by the continuous exhaust flow of evaporated N2 gas coming out the end.
The tube will be coldest near the jug, and progressively less cold farther down the line.
So it will progress from fine snow to hard whitish ice to wet clear ice to merely-wet tube to dry tube.
If your tube is long enough the gas coming out the end will hardly even be cool.
This has safety considerations:
that metal is potentially cold enough to freeze skin onto it.
Being wrapped plastic wrap or tape or paint would help.
Once it grows snow it is OK to touch the snow and knock it off,
but then you have to not touch until it grows some more.
Grabbing it hard would be the only real no-no.
The emergency response to free a stuck hand would be
uncorking the bottle to stop the cold-gas-flow,
and pouring a jug of water over the pipe and hand.
But really, your version with 1/4" tubing and slow gas flow
will not have much chilling power, will not be very dangerous.
If I had a way to keep it out of reach except when I am supervising,
I would consider trying this with a few kids at a time.
Maybe one kid at a time could get some snow, 10-minutes apart.
A tube of thin-wall Teflon instead of metal might be what makes this acceptable.
I would suggest ordinary polyethylene tubing from a hardware store,
but I suspect the thick walls and poor conductivity of plastic makes it less likely to grow snow.
It would be good if I am wrong about that.
Dry ice can probably do the same thing.
Not sure what container to use.
Could be a little easier and safer, maybe.
Ideas, half-baked.
Maybe they will be some help to you.
H2O has a continuous curve of "vapor pressure vs. temperature".
At any ambient vapor pressure, water will condense on an object
if the temperature of the object is below the temperature
of the point corresponding to that humidity (vapor pressure) on the curve.
Simultaneously true: if water condenses on an object below the freezing point,
it will be solid, ice or frost. Else the object is warmer, and it will be liquid water, dew.
Condensing from an unlimited supply of water vapor
can add a lot of heat energy to the cold object.
Air conditioners in Florida have to carry a lot of this heat burden, if I have heard right.
So strangely enough, the key to making frost instead of dew
will probably be to partly starve your cold-place of air-access.
This is probably necessary but perhaps not sufficient.
It is also necessary to make sure that the cold spot
is actually substantially colder than 0 degrees C.
Probably -5C or colder.
Now you can see why cheap refrigerator-freezers are natural frost-making machines.
They are designed to get exactly that cold.
And they have doors, which are usually closed and periodically opened....
I wonder how frost-growing rate changes vs. number of times opened per day.
(It cannot be a frost-free or automatic-defrosting type.
If you have an old kitchen junker with defrost, it is not hard to disconnect the defrost-timer.
Maybe some used-appliance store will do it for almost free.)
Jim Swenson
There are a number of experiments you can do. Given the age level,
I would recommend not trying to "explain" too much. They have so little
experience with the effects of temperature and dew I think "Gee Whiz" is
more impressive than trying to explain the underlying science. I suspect
they are not ready for that just yet. Your idea with Epsom's salts (magnesium
sulfate heptahydrate) is a good choice. Another impressive crystal-former is
urea. It is non-toxic and readily available from garden stores. You can
dissolve the urea in water, and let the water evaporate. It tends to form
large crystals. In addition, you can dissolve the urea in a warm solution of
gelatin. Not too concentrated gelatin. Dip a microscope slide into the
gelatin/water solution. The viscosity (thickness) of the solution will slow
down the crystallization process so that some very large crystals will
result.
The operative principle at this age level is not too heavy on the
science, but rather a demonstration of the "magic" of science. You can even
try mixing the Epsom's Salt and the urea -- just to see what happens (I
do not know, either.) Here, the objective is to see "something" happening.
There is some solid science history associated with urea. It was the
first organic compound made directly from inorganic substances. Before that
time it was thought that the formation of organic compounds required a "life
force". For your reference do a "Google" search on the term "urea".
Vince Calder
Adrienne--
Introduction
Many many many science activities for Pre-K and K environments are actually very difficult topics that graduate students in the sciences have great difficulty with. One example is the very common, "sink and float." An iron nail sinks, but an iron boat floats. There are many misconceptions that are instilled in this activity, and unless there is a very good instructor who can explain the subtleties around this, it is not appropriate. Also, many of the activities are activities, and not explorations. The first link in this section, below, seems to do a good job of designing an exploration at the age level you are teaching. The second link is not as good, but has excellent ideas that can be utilized with the first site's methods. The third link is a book. I have never seen it, but NSTA usually does their homework and produces an acceptable product.
http://www.easy-science-fair-projects.net/kindergarten-science-fair.html
http://chemistry.about.com/od/sciencefairprojectideas/a/kindergarten-
science-projects.htm
http://www.nsta.org/store/product_detail.aspx?id=10.2505/
9781933531021&gclid=CJKL7_7mqK0CFSwBQAodhxezkw
That said, I want to address a few other things.
1) BE PROUD that you are teaching the young ones. This site serves K-12 and teachers in these areas. You more than qualify and we salute you for trying to instill appropriate instruction. You are working at a great handicap in that you have no science curriculum. In our very limited way, we will try to support your efforts, and get you on the road to designing your own curriculum and explorations. The recent research shows that developmentally, a controlled experiment is something that these children do intuitively (recent research supports that--I think it was reported in the NY Times Science Tuesday section in the second half of year 2011), I am not clever enough to create such learning environments. Time to change my attitude and try it out on my grandchildren, in a few years, I suppose. But you are in the lucky situation of knowing this age group and are willing to make meaningful activities for them.
2) ALL science is relevant to this age group. If simplified enough, the Higgs Boson research at CERN would apply. I would not worry too much about relevancy, as they are intrigued by everything.
3) Crystals (finally!). Safety first: Goggles. Yes, this is not dangerous, but it is good practice. It also makes fun photos and bragging rights. Get a low power microscope or good magnifying glasses. I prefer something simple that is intuitive, so I would use 5x or 7 x magnifying glasses. Look at salt from a salt shaker. Then, dissolve it in warm water--as much as will dissolve, leaving some on the bottom that will not dissolve (saturated solution). This may take several tablespoonfuls depending on how much water you use. I would use a cup and a tablespoonful, but if you have many scholars in your class or if they are messy and likely to spill, make more. You are the expert on this. Take a few drops and place it on a watch glass (microscope slide, plate, etc. Since this is crystals, you want to avoid paper and the like since that will create a confused picture), and put it away for another day (it needs evaporation time). Along the way elicit questions about describing it, draw pictures, etc. Use a camera, if you wish. I strongly suggest you photograph them during their investigations and during discussions, project their photo and ask questions like what were you doing? What surprised you? What did you like? What were you thinking? Have you seen anything like this before? . . .
Ask them to predict what will happen when you put the salt into water. Keep a written record of this. Even though many cannot read, you are modeling some very important behaviors for them. In the post lab, you can bring out the sheets and tell them that you recorded the ideas, and here they are. (If you want to get formal, some of these predictions are actually hypotheses, but why burden them with jargon?) Ask what might happen when it dries? Do we get the salt "back"? . . . You get the idea. Now, look at it under magnification again. Have them tell the story of salt and salt crystals. Formally, we call this the experimental results. If you have photographed all parts of the experiment, mix up the photos and ask them to put it in order to tell the story. NOTE: Some will arrange the photos by theme, others, in the order it happened. It does not matter. There is no single way to tell the story.
You want to try frost in Florida on the correct day under the current climatic conditions? I would rather have a cavity filled without a local than plan for instructional miracles.
Follow-up: sugar
Crystal differences? You bet.
These are safe experiments, as they can be eaten. The great copper based crystals which pose some health hazards can wait.
Your suggestions of Epsom salts: go for it!!!
Next up: crystals with different cooling rates. This may be a bit advanced, but get a few sacrificial test tubes. Melt some mothball flakes and crayons together in the test tube. This can be done in a boiling water bath. Cool one quickly in ice water. Cool the next in sand, and let the last one cool in the bath, slowly. This may take several hours.
Place each test tube into two zipper bags. Crack the test tubes open with a hammer. Then look at the crystals under magnification. Did the cooling time change the crystal sizes? You get the idea . . .
This can then lead into a discussion about rocks, crystal sizes, etc. How did the rock cool? or for sedimentary rocks, you can talk about the size of the crystals in each layer. The possibilities of this goes on and on. Or you can go the route of minerals. . . .
Back-up idea of food absorption of water seems very complex to me. Try making cupcakes in toaster ovens. Do a sample recipe. This is your control. What is the purpose of each ingredient? What happens if it is left our? Doubled? What happens if cooking time changes? You can talk about texture under magnification. Big, little, etc. holes. Evenly spaced or more near edges, top, center, . . .
this is a multivariable problem that can last for weeks!
5) In the literature is an activity in electrochemistry that I find works best with very young children (about age 5) and worst with graduate students. It was done by Irwin Talesnick (a science education professor at Queens University in Kingston Ontario). Simply, it is the "Orange Juice Clock"
http://www.jce.divched.org/JCESoft/CCA/CCA3/MAIN/OJCLOCK/
PAGE2.HTM
I think Irwin got the idea from HIS professor, H. N. Alyea, but I am not sure. Do a scholar.google.com search on this. I think Alyea did this in the mid 1950's. (I must be getting old). He published a number of things for the American Chemical Society, and Talesnick took off with it to foster chemical education and inquiry. I am guessing Talesnick did much of his refinements on this in the early to mid 1980's. Talesnick may be searchable on the web and would enjoy hearing from you if you decide to try this one. I think he lives in Toronto, now. He has been retired for many years.
http://elearning.flinnsci.com/PresentersEGC.aspx?presenterId=62
http://www.s17science.com/
6) Frost, dew, phase transitions . . . this takes a bit more modeling to make it meaningful. Also, it is much harder for them to manipulate. Perhaps after doing the crystal activities above, and a lucky morning happens, take them outside with magnifying glasses to see the crystals. Perhaps have some of the wonderful snowflake crystal pictures that Kenneth G. Libbrecht of CalTech took. Do a Google search for him. Easy to find. I would have this as a lesson plan in my back pocket, not one that you will be able to depend upon.
Please, please, keep up your good work as an instructional leader, role model, and professional. We need more like you who are willing to ask others for help instead of "doing it alone." The educational endeavor, the precious lives of the children trusted to us, and (literally) the future of the world depends on our practices. This is way too important to think that it is an embarrassment to ask others to help you help young minds think. Delores Kohl has set up a whole foundation for education at this period of development.
http://www.dkef.org/
Thank-you for making a difference.
Nathan A. Unterman
Co-Sysop, NEWTON Ask-A-Scientist
Adrienne
First of all, crystals are a result of the uniform arrangement of the atoms,
molecules, or ions of the substance. The crystal grows by adding atoms,
molecules and ions to the existing structure until the structure gets big
enough for us to see.
So you might start your classroom discussion about crystals and how the
crystals that we see are a reflection of the physical arrangements of the
atoms, molecules, and ions of a substance. This URL can provide some
pictures for your classroom discussion.
http://en.wikipedia.org/wiki/Crystal
Instead of trying to rely on the weather, why not just try using the
freezer in a standard refrigerator?
Take a glass slide, dip it in water, put it in the freezer and see what
happens.
Problem is that when you take the slide out of the freezer, the "snowflake"
would melt before anyone saw it, but you would have the same problem waiting
for it to frost outside.
If you had a microscope you could demonstrate the structure of grains of
salt, sand or safe substances from a chemistry lab. But you might also be
able to find pictures on-line. Here is a URL that provides snowflake
crystal images.
http://www.google.com/search?q=snowflake+crystals&hl=en&prmd
=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=W9T9TuLJNKrj0QG00fn
KAg&sqi=2&ved=0CGUQsAQ&biw=1024&bih=574
In the wiki articles, you can click on the small rectangle in the lower
right corner of the photo to enlarge the picture, then you can right click
the enlarged photo and select "Save Image As..." and save the picture to
your hard drive for display to the children. Or you can just right click
the photo in the wiki article and "Save Image As..."
In the google search article, you can just right click the photo and "Save
Image As..."
Sincere regards,
Mike Stewart
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