A lot of you, no doubt, are conscientious homeschoolers and will have done the vinegar and bicarb volcano experiment a long time ago, probably at about the same time as you created the salt dough model of some place or another. I don't know what book these ideas come from, but you see them on lots of homeschooling blogs, and so I'm guessing they're somewhere in book form. Regardless of where they're from, we don't have the book and we've never done the experiment. Until now.
One of our free reads is the excellent living science book The Mystery of the Periodic Table by Benjamin D. Wiker. It's a adsorbing adventure into the the history of chemistry from ancient metal workers of the Neolithic period right through to the reported production of ununoctium and its byproduct ununhexium in 1999. The pages in between introduce us to Aximander, Arisotle, Robert Boyle, Joseph Priestley, Henry Cavendish, Antoine Lavoisier, John Dalton, our old friend Humphry Davy, Amadeo Avogadro, Dimitrii Mendeleev, and Ernest Rutherford.
We have loved learning about these men who between them discovered the elements that make up our periodic table. We walk beside them and make the same discoveries they make. We read their questions, we discover their answers to these questions, be they right or wrong. This, surely, is what brings chemistry to life!
The alchemists of the Middle Ages were on a treasure hunt for gold. On their way they discovered all sorts of interesting chemical compounds, and more importantly, they recorded what they discovered and how things behaved. Some of the most important substances discovered by the alchemists were acids ( sulphuric, hydrochloric and nitric). Acids were useful for taking substances apart in order to find more simple ones.
The reaction of vinegar as acetic acid and sodium bicarbonate would have been very familiar to these ancient alchemists. The reaction produces something that is totally unsurprising to us, but which the alchemists didn't even see: Air.
Take a look. Put some vinegar in a plastic bottle and pour a tablespoon of baking soda into the neck of a balloon. Pull the balloon over the neck of the bottle and pour the bicarb into the vinegar. Hold on to the bottle!
Pretty cool, eh? Since vinegar is a weak acid and baking soda is a weak base, the reaction we performed is an example of an acid-base reaction, although the alchemists didn't know that. The equation is shown below:
HC2H3O2 + NaHCO3 -- > NaC2H3O2 + H2CO3
Acetic acid plus sodium bicarbonate makes sodium acetate plus carbonic acid.
The H2CO3 (carbonic acid) then breaks down into water and carbon dioxide:
H2CO3 -- > H2O + CO2
Carbonic acid makes water and carbon dioxide!
We tied off the necks of the balloons to capture the CO2, and then had a bit of a play to observe how the denser gas behaved when compared to a balloon filled the ordinary way. Have a look. The pale balloon is filled with CO2, the dark with air.
Yep, the CO2 filled balloon fell more quickly. This is sort of intriguing, since Galileo showed back in 1580-something that falling objects accelerate at a uniform rate, no matter the weight of the object. So why does it fall faster if it is not because of air resistance nor weight?
Of course the answer is the density of the two gases. Remembering how a stone sinks in water and a piece of wood of the same shape floats, we can apply this to our gases. The CO2 is much denser than air so it falls quickly. The balloon containing expired air (containing a little CO2 but not much) is also denser than air so it falls too, but not so quickly. At standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m3, about 1.5 times that of air.
Balloons filled with CO2 behave differently from air filled ones for other reasons too. They're different shapes for that matter. The CO2 balloon deflates more quickly, despite the CO2 molecule being larger. They're quite amazing things to look at and ponder over, these balloons. So we did!
You can see that I'm no longer talking about The Mystery of the Periodic Table, but that's just the point. A chapter devoted to Alchemy has brought to life ever so much more chemistry than just that. The whole book is like this. These are fascinating stories about very human men. Men who made mistakes, but who made very valid and important contributions to science all the same.
We're loving this book. Can you tell?
I've started compiling a list of Living Science books. There are lots of these lists out there, but I'm afraid that my opinion of living science doesn't necessarily agree with everyone else's. My list doesn't have many books on it yet because...well...because we haven't read that many yet, and I want to read them before I list them. As my daughter gets closer to secondary school that is going to change quickly.
Books dealing with science as with history, say, should be of a literary character, and we should probably be more scientific as a people if we scrapped all the text-books which swell publishers' lists and nearly all the chalk expended so freely on our blackboards. The French mind has appreciated the fact that the approach to science as to other subjects should be more or less literary, that the principles which underlie science are at the same time so simple, so profound and so far-reaching that the due setting forth of these provokes what is almost an emotional response; these principles are therefore meet subjects for literary treatment, while the details of their application are so technical and so minute as, except by way of illustration,––to be unnecessary for school work or for general knowledge.
Charlotte Mason A Philosophy of Education pp 218-9
Miss Mason had rather strong opinions about the teaching of science. Do you agree with her? I do sorta. I am inclined to think that one could manage a science education without textbooks, provided living books like The Mystery of the Periodic Table are out there. Certainly there are some terrific science books in the AO line up. Secrets of the Universe by Paul Fleisher, our Physics text for this term is a case in point. Absolutely sublime, this book is. True. I am not hyperbolising even a little bit here. My Living Science Books project is an attempt to gather together a list of these books. I'll create a tab up top for it when I finally list it. I'd be interested in your recommendations at that point as well. I don't know that I agree with Mason that technical science is not relevant for school work or general knowledge though. My head is filled with such trivia, as is my husband's. To a lesser extent, Jemimah's is too. Maybe Miss Mason wasn't a science nerd, but I am, and I'd like to give my daughter the opportunity to love science too. So far so good!
What are your thoughts on teaching science, particularly in the secondary levels? I'd love to hear your thoughts and experiences. Do you have a favourite living science book?