Tuesday, April 23, 2013

Crystallization

Salt crystals under a microscope


We have had a lot of fun using Building Foundations of Scientific Understanding (BFSU) book the last few weeks.  Our lessons on Mixtures and Solutions, Rocks and Minerals, led us to some very easy crystal growing.  The boys learned that a crystal is a piece of mineral that exhibits a characteristic shape.  We observed salt crystals straight out of the box of table salt under our Magiscope and saw that they were all shaped like cubes.  

I used to think that "Cosmic Curriculum" was some kind of hippy-dippy or Waldorf idea that had something to do with nature as goddess or celebrating the solstice.  What the Montessori idea of "Cosmic Curriculum" ACTUALLY is, is the idea that the world isn't divided up into subjects like it can be in some schools (reading, writing, history, astronomy, geology, chemistry...) but rather is all interconnected and is best learned as such (decompartmentalized learning).  It is also idea of presenting the child with the big picture first and then showing them the pieces, which is the opposite of the way children are often taught (whole-to-part rather than part-to-whole learning).  This crystal work is a good example.  Is this chemistry?  Geology?  Well, both...and more.  I am really happy with how the Montessori Great Lessons keep the topics interconnected and also with how well the structure of BFSU is working in tandem with that.

making a solution of water and salt

I was a little surprised when the instructions in BFSU called for making crystals three different ways, each using a tablespoon or so of salt in a cup of water of non-specified temperature.  I did NOT think this was going to work.  I always thought that you MUST make a super-saturated solution with a LOT more salt in boiling water.  I decided to try it anyway.  If if it DIDN'T work it would be a perfect segue back into the Montessori album to do the presentations on super-saturated solutions.  If it DID, it would be such a nice, simple, non-threatening, low-effort step into the world of crystallization.  One extra reason I am particularly enjoying BFSU this year is that the traditional presentations in the Montessori albums can get really intense really fast.  However, this year I am not teaching two elementary students.  I am teaching one elementary student and one primary student (No, Me Too is not elementary yet.  He is approaching six but is still in a primary plane of development.).  The lessons in BFSU are just right for both of them as well as an excellent door-opener to lead Kal-El into some of the Montessori elementary lessons as well.

three salt crystal demonstrations

For a long while our window seat looked like this.

evaporation used to discover substance dissolved in water

BFSU recommended using dark (navy blue, we found black), plastic plates.  Two plates were prepared with the salt solution described above.  One of the plates has a third plate inverted on top to slow the rate of evaporation (which should yield larger crystals).  

salt solution climbing a paper towel

The third tray has the salt solution in a jar with a piece of paper towel hanging down into the solution from a straw.

The boys learned in our mixtures and solutions lesson that there are ways that one may detect if one or more things are dissolved in water:  color, smell, or taste.  This introduces a fourth method:  evaporation.


salt crystals on plate after evaporation

We are still waiting for the covered plate and the jar to complete their work.  However, the uncovered plate was ready in just a few days.  As you can see, the salt shows up beautifully on the black plate.  We put the plate under our microscope, but obviously we could only view the formations along the edge.

examining salt crystals with a Brock Magiscope


One of the many things I love about our Magiscope (in addition to requiring NO electricity, being nearly impossible to break, inexpensive, and strong enough to use through high school chemistry. Click here to see my original review.) is that you can take the tube right off the stand and use it in your hand.  This is great for looking at the water in the tank of an aquarium at the zoo, or in this case looking at salt crystals in the middle of a large plate without scraping them off and preparing a slide.

salt crystals under a microscope

This is a picture I took of what we saw.  All I did was hold my camera as close as possible to the eyepiece and snap a shot.  Some of our cameras allow us to do this, and some don't.  I've also done this with my iPad or my husband's phone.  No special microscope camera necessary!

We have a lot more crystal growing ahead of us!  We will do the super-saturated solutions soon.  We also have a lot more different kinds of crystals to make. Stay tuned!









2 comments:

  1. Fun! And what a nice discovery that regular cameras CAN work with the microscopes ;)

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    1. Thanks Jessica :) Our little point and shoot camera's and our old SLR wouldn't do it for me. I think it was user error more than anything else. I probably needed a different setting because the focus thing kept moving in and out really fast and making a lot of noise like a crazy robot. Our new SLR just took the picture. Phew. Although, it is just as easy to use the phone or the iPad anyway. I plan to get Me Too a camera for his June birthday so hopefully he'll take over the microscope picture taking soon so that the ADULT isn't the one having all the fun.

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