Tag Archives: model cells

Year 9 diffusion

Good morning!

My Year 9s have finished their animal/plant cell introduction to iGCSE with an exercise where they pretend to be Martian scientists who have taken two samples of life from Earth – a geranium and a student – and are trying to figure out whether they’re just slightly different versions of the same thing, or whether they are fundamentally different. It’s a fun way of getting them to work out the key classification points, without actually telling them.

They’re now into diffusion as a logical extension of this – what do cells need? And how do they get these things? Always keen to try something new, I started this year with Bill’s exercise (attached). Like all great ideas, it’s deceptively simple. But look at it in a bit more detail, you start to see not only why is it fun, engaging and challenging, but also why it works so well as a learning activity. Note the lack of preamble, no “today we’re going to study diffusion…” introduction, just straight into a “do this and figure it out” approach.

It’s fun – they love the little cubes (though they were disappointed to learn about their lack of edibility) and are genuinely intrigued by the colour change. They can explain this at one level – the challenge is to push them beyond the “acid is moving into the cube” description, to something more rigorous about particles. But they quickly see the effect of concentration and by the end of the activity they’ve basically worked out the definition of diffusion for themselves, and seen/measured that it happens more quickly if the difference in concentration is greater.

I’m following this up with an adaptation of my olde introduction to diffusion (attached). As well as making lots of different sized cells, they’re also going to compare diffusion rates at two different temperatures. Again, they work it all out for themselves. The questions are for homework.

Next week I’ll tell you how I move this on to multi-cellular organisms and maltesers…

Have a great week/weekend!


1LT1 – Flipped diffusion in jelly blocks 1

Acid bath and agar blobs with temperature NOV 2014