Monthly Archives: January 2017

Plummeting Teddies

Not a Biological Burbling this week, but a Physical one. What shall we call it? Physics is not my strong point. Physical Fumblings, perhaps? Hmmmm, maybe not.

Anyway, I’m teaching Year 8 Science. Each term has a topic and we’re half way through Forces….

Now I never got on with Forces when I was at school. I hated the apparent abstraction. Worse, I hated the fact that I didn’t understand what was going on. Sure, you can feel the force of gravity pulling a brick down, but no-one could/would explain how a stationary, inert table exerts an upward Force. Where has this Force magically appeared from? It wasn’t there when the Brick was off the table. And even quite recently, before I had to immerse myself in all of this stuff, I got quite cross and frustrated because a moving object was said to have balanced Forces – which just didn’t make sense to me.

It seems I’m not alone. From talking to the Head of Physics and others, from teaching this topic last year, it’s clearly a conceptual problem that lots of students have.

So when I sat down to re-write the KS3 SoW for Years 7&8, I had to get my head round it – after all, you can’t teach anything effectively if you don’t understand it. But also, having an insight into why students might find it difficult is vital for planning an effective teaching strategy. Indeed, if an idea or concept is so blindingly obvious to you that you can’t comprehend how someone else might not understand it, you’re unlikely to make a very good teacher. And if you’re what I now call an Ocado Teacher – someone who confuses Teaching with Delivering information – then the problem doesn’t even exist.

Last year, when I did this for the first time and was still feeling my way, I tried loads of stuff that didn’t work. Pebbles dropped into cylinders of water didn’t work as a way of investigating/understanding how Forces change on a descending object. I wanted something more interesting, more relevant, more fun. And I wanted it to work.

What I felt was needed was to take things right down to basics and provide the underlying mechanisms. Wind resistance, for example, is a familiar Force, we can feel it, name it, but if all we do is give it a name and an arrow then we’re not helping students understand what it is or how it might vary, other than with some statement like, “the wind is blowing harder”.

This was clearly a job for Cuddly Ted!

Actually, I ended up using my prized collection of fluffy birds, as we hadn’t had time to put in an order for 30 or so small teddy bears. Bear (ho ho) with me…

Context – we had covered some introductory stuff on different types of forces. They had carried out experiments with slopes and surfaces and sails, to demonstrate gravity, friction and air resistance. This was mainly about experimental design, but  we had discussed, briefly, the idea that a bigger sail has greater air resistance because it’s bashing into more particles in the air. We look at the video of a Physicist shooting himself under water. This is very cool.

Why isn’t he dead? Why does the bullet stop???

We’ve also drawn some Forces arrows. And we’ve done some Galilean “gedanken” experiments to think about moving objects in the imaginary absence of friction…

slopes-and-surfaces-3

Now I wanted to focus on what happens when you drop an object from a height – what changes and, crucially, why?

A small bear/fluffy bird, dropped from the top of the Physics fire escape staircase falls, with obvious predictability, to the ground. The class is very happy with the idea that it is being pulled down by a force called gravity (there’s a nice exercise on the Nuffield Physics Teaching site which has students lifting a brick with their eyes closed so they can feel the imaginary elastic band that is pulling everything towards the centre of the earth- they’ve done this in Year 7). They’re also happy that while the bear/bird was in my hand, the Forces were balanced, but that once I let go, and things changed, the Forces had become unbalanced.

At this point the language becomes a bit vague. Why did it fall? Because gravity was pulling down and there was nothing underneath it.

Nothing?

Well, only air.

Only air ????? Is air nothing? Did our bear/bird, now looking somewhat damp and bedraggled (it was a wet day) experience no other forces than gravity on its rapid plummet?

They remember our discussion about air resistance and atoms. The bear/bird is bashing against atoms as it zooms through the atmosphere. They blow on each others faces and experience a trillion zillion molecules bashing their skin…

So how could we save our bear/bird from a grisly plummety type of death?

Of course. A parachute.

Teams of 3. Some thread, a bin liner, some paper clips, scissors and a fluffy bird. Who can make the best parachute?

30 minutes of joyous competitiveness.The Ocado teachers hate this kind of activity – they’re not delivering anything! how can the children be learning if they’re not taking notes???!?!? Well, I could make the cheap point that the students will remember this lesson longer than any note they will ever take. but, of course, it’s all about stimulating the interest and curiosity and enjoyment that will make them want to learn the difficult bit that follows.

So, one by one, the contestants drop their parachuted birds from the staircase and I time the descent. The winner is aloft for over 3 seconds! The loser, well, their parachute didn’t open…

Back inside the lab., we tidy up, spruce up the birds, and then start work on the attached exercise.

sorting-out-forces

What I’m trying to do is provide an explanatory framework for this counter-intuitive notion that a descending object can have balanced forces. It’s structured like a story, but it’s also visual – look, there are the atoms that you bash into when you jump out of a plane. The more you bash into per second, the greater the air resistance…. why might this change…?

Have a go. Tell me what you think. Better still, if you know a Physicist (and most of us probably do) try it on them. What do they think?

For the Year 8 girls, it provoked lots of, “Oh, I see….” which is one of my favourite reactions in teaching. Come the test, will they all draw the arrows correctly….?

I’ll let you know! Back to Bioogical Burbling next week.

 

Excel and Catalase

A belated happy new year to anyone still out there in burble land.

And a brief explanation of the lack of burbling in recent months. Last term was the busiest and most stressful term I can remember in over fifteen years of teaching. For a variety of reasons, I became thoroughly disillusioned with teaching and lost all motivation to write up ideas in what little free time was available.

I cheered up a little when someone provided a link to this wonderful satirical blog on teaching https://robertpealhistory.wordpress.com/blog/ ( the  blog article: “Keep it simple, stupid”).

But then I found out that far from being satirical, it was the real deal. Worse, it’s an approach to teaching that is endorsed by that great educational reformer Michael Gove AND the Daily Mail.

Gulp.

OK, Mr Peal is working in a completely different type of school. He’s teaching a different subject. He has challenges of classroom management and pupil behaviour that I rarely, if ever, encounter.  I’m generally in agreement with his view that Powerpoint should be used to show images, not provide the backbone of a lesson (though he seems woefully ignorant of the potential for its interactive, non-linear use). And, of course, children like structure, reliability, the security of knowing that they’re learning.

But that doesn’t mean a lesson can’t also be fun, challenging, imaginative, varied, surprising…. The very last thing a teacher should be is….

Boring.

So, in the interests of balance, The Burble Is Back.

And where better to start than with Excel spreadsheets.

Ahem.

Context – Year 9 Enzymes. They’ve covered the basics of enzyme kinetics, largely discovered by themselves, and are now looking at different ways of measuring enzyme activity (rate of substrate breakdown, rate of product formation, etc).

The investigation was this splendidly challenging Yeast Catalase and Temperature activity – pretty much the same design that I use with Year 12 when they try to demonstrate a Q10 effect and have to evaluate whether and why their data does not match the predicted pattern.

yeast-catalase-and-temp-expt

I’m not expecting Year 9 to get a Q10 curve, but it’s a self-differentiating, challenging activity that is exciting, different, fun, surprising…

Now you can see from the attached homework questions that I want them to analyse and evaluate their results. But there are lots of potential problems with this. Some groups only manage to cover 2 temperatures. Others have, shall we say, technical difficulties. Others have data that shows no coherent pattern at all. Students trying to work with this kind of data inevitably end up confused – and we’re back to that horrible question that negates scientific curiosity, “what’s supposed to happen?” We need to use ALL the data in some way.

So look what happens if you get them to enter it into a class Excel spread sheet (names have been changed…) which I’ve also projected on to the white board.

9g-catalase-and-temperature-spreadsheet-december-2016-for-blog

Why does this help? Well, firstly, it adds a level of interest, and dare I say it, competitiveness to the lesson. For some reason, they just love putting stuff on the board. It also helps keep them very busy and focussed (good test of a successful lesson, I think, is when the bell goes and the students looks surprised that it’s the end of the lesson – has the time really gone that quickly?). And, vitally, they still have ownership of the data – these are THEIR numbers – they become quite attached to them in a way that just can’t happen if you pick a problem out of a textbook.

Now with our current timetable, I use the entire double lesson to carry out the practical and collect the data, so we return to the numbers in the following single. I project the completed table on to the board and immediately lots of important learning outcomes start emerging.

First, despite all the best efforts of “Shall we do the fandango?”, much of the “noise” has disappeared from the data and the means show a clear, enzyme like pattern. The value of doing LOTS of repeats is immediately apparent.

But why else might we do repeats? What else can we see? Yes, some of the numbers seem out of place. What could we do with these numbers? A bit of discussion and they see that by looking at the overall mean, and then comparing it with individual numbers in the table, we might choose to eliminate some of the data. At which point I produce this version of the table as a handout…

9g-catalase-and-temperature-analysis-exercise-january-2017

… and get them to identify anomalies. I give them about 5 minutes to do this, and then it becomes a bit like evicting contestants from the Big Brother household. Or The Weakest Link. We discuss rigorous criteria for eliminating numbers (rather than just a vague sort of “well, it doesn’t look right) and then vote on which numbers are out.

And because the numbers can be removed, live, from the projected Excel spread sheet, it automatically recalculates the mean, far more quickly and accurately than they could ever do themselves. It means they’re focussing on the actual numbers, rather than fiddling round with calculators. The rate for 70’C now drops, correctly, to zero. We can discuss why two groups found activity at this temperature and we have an evaluation point – they fess up, admitting that they probably didn’t keep it in the water bath for long enough before mixing the reagents, so there wasn’t time for the enzyme to denature.

Once this is over – and the discussion and voting is much more fun than you might imagine – they can copy the new means into the Revised Mean Mean row and they’re set to plot the graph and answer the questions.

And there goes the bell…