Saturday, 1 March 2014

The weight of air (stand back, we're doing science!)

In another attempt to restore balance to what has become our far-too-table-based home education, I've been trying to carve out some time for some hands-on science.

I've been attempting to finish Ellen McHenry's 'Cells' with the two boys, but there are always other priorities for the eldest (IGCSE-related) so it's been slow progress.

But these past couple of weeks we've got as far as the dissolve-egg-shell-in-vinegar-and-demonstrate-osmosis-by-dunking-egg-in-syrup-or-water experiment.

It was supposed to take about 3 or 4 days for the egg shell to dissolve to the point where there was just a floppy sack of white and yolk. 8 days in and, apart from some minor bubbling at first, not much was happening. Just as I was wondering how much longer I would have to display softened smelly eggs in vinegar on our windowsill for the neighbours and anyone passing our house to see, I had an idea.

The problem, I deduced was that, being a cheapskate thrifty person we'd used a jar of old pickled onion vinegar. (We have a plentiful collection of random jars of pickled onion vinegar in the cupboard taking up much needed space, but alas I simply cannot dispose of them.)Trouble was, this old pickled onion vinegar was probably more dilute than nice fresh shop-bought vinegar...and it had year-old bits of pickled onion skin floating around in it which may have somewhat contaminated the experiment.

When we changed to fresh vinegar the eggs positively fizzled and the problem of *there's nothing happening mummy* was solved. 3 eggs fizzing on our windowsill...and later 3 eggs floating in syrup and water.

Does air weigh anything?

This is the question recently posed by the other science course we're using Building Foundations of Scientific Understanding (BFSU) Vol 1

 With a bit of scientific experimentation (otherwise known as fiddling the results) we discovered that if you dangled two bags on strings on a ruler, on a shoelace from the handle of a saucepan, over the edge of a table, then, yes, air does actually weigh something. It was just a little don't-move-or-you'll-mess-it-up amount of something.

We really don't need to be starting yet another science 'course'. We have a huge shelf of science books, many of which we never get around to reading or using. But... I love the idea behind BFSU. I love the discursive aspect of the course. I love how it's not just another 'do this experiment, get this result' science book.

But it is a very wordy book, and it does take some prep to be able to use it. The parent really has to be on board to lead/steer a discussion. It's written for a class of same-age children, so although it is home-ed friendly, it's not always easy to implement with a smaller group of different age children. Trying to lead a discussion ds2 (who is 12 and knows most of the answers)  and dd (who is a young 10 and would rather be blowing bubbles than pondering the difference between a liquid and a gas) takes some managing. The book is also supposed to be approached in a manner whereby the kids are doing biology and chemistry and physics side-by-side in an ongoing web of related activities and discussions. It does my head in just thinking about trying to juggle all of that. I've not seen anything like it before and it takes some getting used to. This is our second attempt at the book, and I'm hoping it will get easier as we go along.

And today...our BFSU science required some blowing of bubbles ('little packages of air particles')

And not all science is *that* sort of science. This is science too. At least I think it is science. Because I can't understand why else a child would play on the computer with a box on their head. Surely it's *got* to be an experiment.

1 comment:

Paula Turner said...

love the "too-table-based-education" comment!