Saturday, 30 September 2006

S103: Potatoes have feelings too.

Your mission, should you decide to accept it, find out the water content by percentage weight of your average potato. This is a block one experiment.


After some time spent reading through the book, it was interesting to have a break and start some practical skills. Lets see, by heating the potato in the microwave, we can drive off all the water held in its cells, and see how much of it there is.

Now - what equipment do we need.
  • A microwave - check!
  • A potato or two - check (Maris Piper, unpeeled, 3).
  • A calculator - check
  • Scales - check (digital ones, weighing in 5g increments - wooooh!)
  • Notebook - check
  • 5 year old helper - hmm, not mentioned in the notes.


First job, find a suitable plate. I decide I want a lightweight one so that it won't affect the scales too much. If the plate weighed 10 kg, the scales probably wouldn't be very sensitive to a few grams change in weight.

Now - slice up the potato, and already my helpers attention had started to wander. I wanted to slice them thin for speed, but decided I just needed to get on with it while the attention was focused on him trying to switch on the calculator.

Right - so into the nuke and blast for the first 4 mins. Out it comes, and its a little warm. We measure the weight, and I write down my first figures. I return the potatoes to the oven, while my helper tries to weigh his hand.
After a little bit of dissuasion, he's back on the calculator, now having got it switched on. So I ask him to type in the numbers whilst doing the arithmetic in my head as a double check. We have a few false starts...

By now the next 4 mins is up, so I do another weighing. I hear the calculator clatter to the floor.
Anyway, another weight recorded, and back to the oven. I turn around, and there he is is, trying to weigh his head this time, and read the numbers at the same time.

We do some more calculator work, and then he wants to know why crocodiles and caimans don't both live in the amazon.

The microwave peeps, and the calculator clatters to the floor. Another measurement, and my helper is getting quite good at subtraction. I manage to persuade him that weighing other parts of his body is really not worth it.

The next record and the calculations are definitely wrong, where we'd been subtracting 55g, he now wants to see just how many 5's he can get on the display. I think I've just found a new source of errors...

We're down to two minutes between bursts now, and there is barely time to drop the calculator and recover it between the measurements, but he rises to the challenge majestically.

The potatoes are now looking distinctly crisp shaped, and are very hot when trying to separate them.

Another couple of blasts, and there is no change in measurement, so I pronounce it done. The calculator clatters to the floor one last time in celebration.


A bit of calculation, and I come up with a figure of very slightly over 80% for the water content.

I reflect upon the geniuses whose shoulders I am standing on, Newton, Galileo, Darwin, Einstein. I wonder if they'd have seen further with a little helper?

Friday, 29 September 2006

Starting S103

So september comes around, and with it a large pack of books, papers, CD's and DVDs. Included was
  • Three text books
  • A pair of DVD programmes
  • A pair of DVD course materials
  • A set of course notes
  • A set of course guides
  • A stop press notice
  • A glossary
  • A folder
  • A bit of black plastic
  • Various introductory and other guides
  • A checklist
  • The first set of TMAs

I unpacked the contents on the kitchen table and tried to make sense of them. There was a lot of stuff there, and it was difficult to untangle it at first. They only send part of the course at this time, as they don't want to swamp you with information and make you run and hide.
However even with this reduced load I found it difficult to make sense of what to read first, second and so on.

They usually have a set of things, so you get a course guide - which is a one page synopsis of the chapters, and estimate of how long each part will take and what other media might be used. Then there is the course notes which have longer exercises to do for each topic. There is the course book too - which is where the main learning comes from. I usually forgot about the other two documents until prompted in the book to read various bits.

I tried going through the things in various ways, but in the end I couldn't really see which was the way to read these things. I gave up and just started reading book 1, The Water of Life which seemed to work out ok. Having done science before, the book was pretty straight forward being a nice gentle introduction to some science concepts.

Meanwhile the OU forum jumped into life. A lot of early comments about things. Tutor groups hadn't been allocated and people were getting all wrapped up in the idea of travelling hundreds of miles to tutorials. Lots of speculation on this that and the other.

It had the definite sense of we were all setting out on a journey together.