Monthly Archives: May 2016

A practical question

Before I launch into this week’s burble, I had a lovely e-mail from Liz, asking if I knew the Tom Lehrer Elements song. Indeed, I do! And my Year 7s also introduced me to another version of the same thing which you’ll find yourself singing in the bath. As for the Tom Lehrer classic, get your class to learn it and then sing along to this Powerpoint where the Elements appear in the order mentioned…The Periodic Table for song only

So last week I burbled on the value of writing your own test papers and questions. I signed off with a mention of the practical questions that I put into the Year 7 and 8 summer exams.

Before looking at them in a bit more detail, here’s why I think you should include some form of practical assessment in end of year exams.

  1. It’s a fundamental scientific skill – of course we should be assessing it!
  2. It makes them take the practical stuff a bit more seriously – yes, it’s fun and motivating, but you also need to be good at it if it’s to have value
  3. It makes the exam a bit different to all their other exams. I try to get them to think of tests/exams as a Fun Frolic rather than a Terrifying Test, and including a practical question really helps with this.
  4. It allows students who have excellent practical skills but are maybe not so strong on the theory to feel good about science

There must be other reasons. If I think of them I’ll add them as I go along.

So, Year 7s. Huge emphasis on practical work throughout the year. Absurd not to include something in the exam. What could we get them to do? Inevitably, when the entire year group is carrying out an activity – rather than just one class – the practicality of your practical is important – always think of your technician! So I decided against a wet experiment or a burning investigation. Some kind of microscopy exercise would be easy to set up, easy to clear up, easy to mark, and, again, would focus (sorry…) attention on this as an important skill that’s worth getting right.

Their introduction to cells involved actually looking at cork and onion cells, and they built their own model plant cells. So my wonderful technician sourced some old stem TS slides, blocked out the original labels, and we were good to go. The logistics of the exam meant that two girls had to share one microscope – so one did this question first, the other did it later. Not a problem.

Now then, the interesting bit. What did I want the exercise to cover?

OK, first bit, could they actually use the microscope? You know, turn it on, put the slide in the right place, focus on the tissue accurately. See something…. I tried to keep it simple.

Observe the slide under low and medium power (to keep them away from the fiddly fine focus of HP). If they managed to do this without assistance, they gained one mark (but they were instructed to ask for help if they couldn’t focus the microscope – as they would lose the skilful mark, but gain access to all the other marks).

Draw one cell. Three marks.

Here I wanted to see if they understood what a cell was when looking at lots of them. So a drawing of a single cell, regardless of the quality of the drawing, gained one mark. Lots of them drew hundreds of cells. Never mind – did their drawing resemble the specimen? If it did, then lovely drawings of lots of cells gained the next mark. Deranged scribbles of one cell did not.

The final mark was a general one for quality of drawing. Did they use a pencil and fill the space? Was it drawn not sketched? Did it have nice clean lines and no shading? If so, the final mark. Next year, I think I’ll award two marks for the quality of drawing to really reward the careful, patient, observations.

Finally, could they interpret what they could see?

Do you think your drawing shows an animal cell or a plant cell? Explain your answer. Two marks.

Plant cell got them one mark. I hoped they would pick out the cell walls and/or infer the large vacuoles for the second. “Plant cells – because they’re not moving around” only gained one mark.

Did the question achieve what I wanted? Well, they certainly took it very seriously. There were lots of quite beautiful drawings and fewer total disasters than you might expect. The mark allocation differentiated nicely and staff reported it as easy to mark.

The Year 8 practical exam questions was more challenging. And I’ll talk about that next week….or rather, the week after, as half term is upon us! I’ll be camping with my family on the Isles of Scilly. Hope you have a good one.

Question Time

It’s Summer Exam Season and the Years 7&8 have emerged, slightly shell-shocked, from their 3 days of internal exams. As you know, if you’ve been a burble-follower, re-writing the KS3 SoW has been my major project of the past two years – and producing an exam that reflected the aims and objectives of the new course was obviously part of the job.

I’m always surprised by how few people write their own tests. Ask someone in my department to put together a test or exam, and they’ll spend hours looking for past paper questions (accompanied by that sacred script, with its ineffable text, The Mark Scheme). But they never put a question together of their own. I think this is a great shame. Asking questions is an essential skill of good teaching and the more you practice it, in whatever format, the better you become.

I also think it’s an enjoyably creative process – coming up with some original slant on a familiar topic – and, perhaps most importantly, it enables you to tailor the exam to your students. Bespoke tests that are suitably interesting, challenging, personal (I like to insert jokes to try and fight the assumption that exams are necessarily grim, unpleasant affairs)!

Exams put together with random questions from old GCSE papers lack cohesion as they have no theme. They are often overly simplistic for our very bright students, and also look horrible. With all the power of Microsoft Office at your finger tips, and all the visual resources that Google and Science Photo Library can provide, there’s no reason not to give it a go. Plus you have a permanent, electronic copy that you can tweak, edit, improve in response to your students’ answers, and which doesn’t fade from endless re-photocopying.

Example – the Year 8 Summer Exam, newly written this year. I wanted to include a question on Forces. The old paper had two random and entirely unconnected old GCSE questions – one on a gannet, the other on a bungee jump. 4 marks.

But I prefer A-level style questions which start with a context and use it to develop a theme, starting with easy questions and gradually becoming more challenging and differentiating.

Hmmmm. What would provide topical and interesting and possible question material for something on Forces? I forget what prompted it, but I suddenly remembered the record breaking altitude jump. Felix Bumgardener, or something. At which point I started doing some research. Lots of great pictures, lots of fascinating information, and perfect material for the learning outcomes I wanted to assess. Here it is:

Felix question

The Year 7 exam was equally fun to write. This year I was able to include a question on Periodic Table interpretation based on their Mendeleyev role play exercise (see The Lesson From the Black Lagoon ). They just had to predict 2 properties for each of the mystery elements shown.

simplified periodic table for Year 7 exam

Next year I need to make it more challenging – but their answers were a reassuring measure of how memorable and effective that lesson had been (especially as they hadn’t written anything down!).

The other thing I included in both Year 7 and Year 8 exam was a practical question. The Year 7s had to use a microscope to observe some plant tissue and draw a cell. The Year 8s had three mystery solutions that they had to identify with a number of chemical tests. More on this next week…

Immuno-apology

Well, that’ll teach me to wade in all strident and authoritative.

It’ll also teach me to listen to that little nagging voice in the back of my head that suggested I might want to double check before sounding off….

Ahem.

So, turns out that B-cells do present antigen.

In my defence, it’s a level of Immunology I’ve never encountered – and I do research these things pretty thoroughly.

And when you check the references….

… it’s way beyond anything an A-level student would ever need to get their heads around.

But, I’m happy to stand corrected. Thank you Bill for the gently worded e-mail….

In future, I’ll just stick to the burbles! The ranting gibberish (my gibberish) on the previous post has been deleted.

 

Brine shrimpery update

The hatch experiment might not have been successful this year, but Year 8 brine shrimp bottles have worked beautifully.

brine shrimp bottle

What’s quite nice is that there is an initial algal population boom – the bottles go dark green – and then, as the shrimps hatch and eat and grow, the bottles become clearer and clearer. I wonder if this could be measured with a colorimeter over time? It’s certainly a great discussion point. And makes up for the failed hatch experiment which I will be trouble shooting in a week or so.

And this exercise was a joyous success.

Savannah Species’ names

Savannah Species’ pictures

– going on an African savannah Safari and creating a food web from the animals they see, identify and research on the i-pads.

Next year, rather than have them all do the same thing, I plan to have 5 or 6 different ecosystems (Rain forest, coral reef, pond, er…..) and they can present to the rest of the class. Having built the food web, work in a perturbation exercise. Insecticides wipe out all the oxpeckers – what happens? The ivory trade exterminates the elephants. What happens? Sleeping sickness annihilates the zebra -what happens? Global warming kills the grass – what happens? And so on.

Was pleased and somewhat surprised by how much they enjoyed it!

Brine shrimp disaster!

Not a great week for new ideas.

I’ve based the new Year 8 Ecology topic around brine shrimps and the wonderful resource developed by Stephen Tomkins and Michael Dockery for the British Ecological Society. You can find a pdf of the full booklet here:

It’s just brilliant – full of superb ideas for practical Ecology based on studies of animals in the lab. My idea was to start with brine shrimp bottles – little self-contained eco-systems – that the students could set up, use for various lessons, and then take home to keep. I also wanted them to carry out the brine shrimp egg hatch investigation, looking at the effect of key variables (pH, temperature and salinity) on hatch rate. There are so many important skills being developed here and it’s a great differentiator as they get to research brine shrimp ecology and make predictions.

In addition, I wanted them to look at the splendid Dunlaliella flagellate algae through microscopes as a route into primary producers.

Better still, I had already used these ideas in other schools and felt the whole thing was pretty much bomb-proof.

Ahem.

Well, starting with the positives, they had a lot of fun. And various skills were certainly developed, particularly that of perseverance when they came to count the 100 brine shrimp eggs for each treatment of the hatch experiment.

But the algal microscopy was a complete failure – nobody could find the startling view of 1000s of tiny green dots gyrating wildly under the lens. I suspect our samples were too old and the alage had all died. Plus the algae really are very very small – even on HP you can’t make out much detail. Next year I plan to buy a few more binocular microscopes and look at the brine shrimps themselves – where you also get to see the algae, crammed into the digestive tract.

Worse, for the hatch experiment, nothing hatched. Under any conditions. For any of the 4 classes. All that work and no results! (my technician would like me to add: all that sea salt! all that marine sand! all that dechlorinated water!). It was all crushingly disappointing and I currently have no idea why – I mean, I’ve done all of this before with primary school children and, as I say, it works. Every time.

Except this time.

So, I’ll have to go and trouble shoot that. Any suggestions? It can’t be a dodgy batch of eggs because they DID hatch when added to the main display brine shrimp tank (well worth setting up one of these if you have space – instructions in the booklet….). They also hatched in the brine shrimp bottles (these do seem to have worked well, and the girls were suitably excited at the sight of the 100s of tiny nauplii swimming around). Perhaps the lab just got too cold – though that doesn’t explain the lack of success at 30’C in the water bath.

All very frustrating and disappointing – but despite all that, the girls were suitably philosophical. They recognised that we were trying to do something interesting and worthwhile and appreciated the effort, even if it hadn’t quite gone to plan. They had enjoyed the lessons setting everything up and we could still talk about the dynamics of an ecosystem in a bottle.

I suppose what I’m getting round to saying is: don’t be afraid of trying something new just because it might not work.

To end on a completely different note – I highly recommend showing this astonishing film on CTLs to your 6th form.