Wednesday, September 28, 2011

Chemical Proportions and Electrolysis

In preparing for Middle School Chemistry with our co-op our family we are going through Matter and Energy: Principles of Matter and Thermodynamics . This volume has two chapters about chemical reactions and the periodic table so it makes a good transition.

The first chapter is about the Law of Conservation of Matter, and while we just read the chapter I've been inspired by something I found here.  I modified it for homeschoolers, taking out much of the school jargon and requirements, and posted it here.  I hope to try it and blog about it soon.

Meanwhile, the second chapter is "How the Elements Combine."  Proust first figured out that chemicals combine by mass in definite proportions.  Dalton realized that some chemicals combine in several but definite proportions, a fact that fit in well with his proposition of matter being made up of atoms.  Next Gay-Lussac showed that gases combined in the same proportions by volume, leading to his law stating that equal volumes of gases have equal numbers of atoms (Avogadro figured out how many.)

This was all well and good, but I was not sure how much they got from this chapter.  I did not have the materials the book listed to carry out electrolysis.  I did an Internet search and found that some people used pencils with both ends sharpened, making holders from Styrofoam trays or cardboard, all powered with a 9V battery.  (See here and here.)  I wanted to capture the gas as was done in the book so we could test them, so this is what I did:

I filled a measuring cup with water and added a teaspoon of salt.  I attached a piece of aluminum foil to one end of two wires with alligator clips. I filled the test tubes with water and placed them over the foil pieces, using the top of the test tube rack to hold them upright.  Finally I connected the other end of the wires to each terminal of a 9V battery.  As you can see at the top of the test tubes gas began to collect.

My boys knew water was H2O, and that meant 2 molecules of hydrogen and one of oxygen.  I explained that electrolysis was "splitting" water with electricity.  I posed the question, "How do you know which gas is collecting in which tube?"  We went through the chapter again.  Proust and Dalton both worked with mass while our experiment was based on volume.  We discussed more about Gay-Lussac's law and asked how definite proportions relate to the creation of water with H and O.  The wheels started turning and they then knew for certain that the tube with more gas had to be the hydrogen.

I do suggest a lantern battery for this, though, because the 9V ran out when only a fourth of the hydrogen tube was filled.  But I am actually a bit glad.  I pulled it out of the water, let the water fall into the measuring cup, lit a match and put it into the mouth of the tube.  The loud whistle and pop was impressive enough to prove that indeed it was hydrogen.

Sunday, September 18, 2011

Mini Science Posters

I first saw this in Biology Inquiries by Martin Shields and I had to laugh.  "Lapbooking for schools," was all I could think, but after having spent a bit of money and time helping my kids make large poster presentations, I thought this was a great idea.

The idea is to put two file folders together just like you would a lapbook, completely overlapping one side of each folder; that makes the tri-fold poster board that will stand on a display table.  Instead of mini books, kids place their information just as they would on a large poster. So instead of creating it as you go through a subject as you would a lapbook, this is meant to be a culmination of learning presented at the end.

This link goes to a blog entry written by a science teacher that shows a mini poster and how to construct it.  This link is to a pdf that gives an example of how to place information on the three panels.

Sunday, September 11, 2011

Middle School Chemistry

Our focus this year is Chemistry.  A long while back I found a great, free resource called Middle School Chemistry by the American Chemical Society.  This 600+ page pdf takes an inquiry approach to chemistry, meaning that students first make observations through hands-on activities and then learn about the concepts behind them. The book has 6 chapters and 38 lessons.

It starts off simply but builds quickly.  The needed specialty supplies, like graduated cylinders and copper sulfate, are few are not needed until later in the book; everything else is around the house or at the pharmacy.

To go with this we are reading The Wonder Book of Chemistry by Jean-Henri Fabre.  It is available at Google Books or The Baldwin Project online, or through Yesterday's Classics in print form.  It covers a lot of what Middle School Chemistry does plus a whole lot more, including a little plant biochemistry.

This is a wonderful living science book.  It's the story of Uncle Paul educating his two nephews, Emile and Jules, through demonstration and conversation.  I hope my boys are as inspired as the nephews are in the book (and that they don't expect that we can carry out the same demonstrations!)

Finally, after working through these, I hope to work through TOPS Analysis (10).  It contains 16 Task Card Activities.  I am supposed to give them one and have them work through the task at hand.  The book gives detailed explanations for teachers so they can get students started if they don't quite understand what is being asked.  But after going through the above materials I am hoping they will have fun exploring the materials in this one.

I will find supporting material on ExploreLearning Gizmos, Adaptive Curriculum, and Discovery Streaming as well, and blog when I can about our progress.