Can you see what it says yet?

For a while now I have used water bubbles (aka super absorbent polymer balls or hydrogel balls) to discuss refractive index and to illustrate the difference between transparent and translucent materials.

You may have seen them discussed on an episode of QI (though I don't recommend the use suggested by Jack Dee at the end of the clip). 

These little balls start out tiny, but can absorb water to grow many times their original size as you can see from the photo.  

Comparing the dry and hydrated bubbles

The waterbubbles, when dropped into water, are almost invisible.  This makes them a nice starter demonstration when teaching refractive index. I start with a bowl of ‘mini bouncy balls’ and a bowl of water.  Tell students that the waterbubbles are ‘magic’ and drop them into the water.  They disappear!  This can be used to elicit some interesting questions and hypotheses about what has happened. 

And they’re a lot less sticky than the pyrex test-tube in glycerine demo that I used to do. 

The waterbubbles have almost exactly the same refractive index as the water, so the light passing through them continues to travel in a straight line without refraction.  That means that we can’t see them and they are invisible.

Even in primary school they can have their uses.  Children are taught that light can pass through some materials (transparent) but not others (opaque).   However, children will also know about opaque materials which let light through, but you can’t see what is on the other side.  In opaque materials the light is scattered as it passes through, and so the ‘picture’ is lost because you’re looking at light from lots of different places on the object.

To demonstrate this, I put lots of the hydrated waterbubbles into a clear plastic container and put it on top of a short poem.  The refraction of the light at the air/water/air boundaries mean that the light is scattered and you can’t see the poem, although you can see that there is something underneath.

Waterbubbles on top of the poem.  They are a model of a translucent material

 

Slowly add water.  As the water covers the waterbubbles they no longer refract the light, and the poem underneath starts to become clearer.

Can you tell what it says yet?

Finally, when all the waterbubbles are covered you can read the poem in its entirety.  The light passes straight through the bubbles, and to you.  

Waterbubbles fully covered with water.  A model for a transparent material.

For older students, you could have them sketch what is happening to the light as it passes through the boundary of the balls, and ask them the explain what they have seen using the terms: refractive index, refraction, boundary, air, water, light.

You are now asking “Where can I get these wonderful water bubbles?”.  The ones in these pictures were taken out of a cheap gel air-freshener, rinsed to get rid of the perfume oil, and put in water to plump them up a bit.  They are used in flower arranging, so a local garden centre or florist might stock them.  I have also bought some from waterbubbles.co.uk in the past.

Starting again.

It’s been a while since I started the blog.  Since I began much has changed.  A couple of year ago I began with the idea that I would comment on science stories published in the news.  However, since then I’ve changed my job and that has given me a different perspective on things.

Nowadays, I’m much more interested in the education side of things.  Perhaps because, having left the classroom, I now have time to think.  Time you don’t have when you’re working in the classroom. 

And then there’s twitter.  A flood of ideas, diatribes and social chat.   

So now I’m thinking that a blog would be a good place to record my thoughts about what I’m reading and pondering.  Probably still science linked, but I suspect that education will creep in quite often.

I hope we enjoy the ride.

Atlas of Risk

The National Health Service website has a really interesting tool on it - the Atlas of Risk.  The aim is to put the relative risks that we all face into context.  It's well animated, and quickly and easily shows different risks to males and females, to different age groups and to different areas of the country.

You can also click through to find out more information about each type of risk.  Great fun, and a very visual way of thinking about the ideas of risk with students - for example the difference between percieved and actual risk, the size of risk and how it is measured, making informed decisions about the management of a given risk and that everything we do carries some form of risk.

I was particularly struck by the difference in risk for males and females in the North East.

Another excellent use of taxpayers money!

Brain Training

I'm sure you've seen the adverts.  You may even have played the games.  Now the BBC is running a mass participation experiment to see if there are benefits of brain training.  You can find the website here.

I think that this could be an interesting experiment to get students involved in.  There are whole areas of How Science Works that could be discussed using this as a starting point.  For example:

• sample size - why do bigger samples generally give better quality data than smaller samples
• experiment design - what are the important features that have been included and why.
  
• ethics - are there any ethical issues that could arise from this?  Who determines if the experiment is ethical?
• community of scientists - who are the scientists that have designed this? what are their credentials
  
• Peer review - how are the results going to be publicised?

 The timescale of the project is such that preliminary results should be available after Christmas allowing the whole experiment to be included in a single year for students.

Handy Websites 1

These website are taken, mostly, from the Summer 09 Teachers Magazine published by the DCSF.  A mixture of chemistry and physics. 

Practical Physics - from the nice people at Nuffield and the IOP. Practicals for all occasions (with risk assessments too!)

The Naked Scientists - Podcast and linked website.  Interesting answers to science questions, and articles about current science research.

Lancaster University Particle Physics Package - Aimed at A level Physics students.

Chem4Kids - American website which introduces children to the essentials of chemistry.  Also available for other sciences.

Future Morph - Site to give students an idea about the range of science careers available.

Planet Science - extensive site developed from the Science year a few years a go.  Lots of fun things to explore.

Web Elements - An interactive periodic table.

Singing Science

One of the things I really like to do in a lesson is to play music which is related to the topic.  Sometimes they are straight-forward, but not always.  Some kids figure out what I'm doing quite early on, and then it becomes part of the lesson for them to guess what the topic is, or how the song is related to it.

Some examples:
Chain reaction (the Diana Ross version of course) for anything to do with Radioactivity.
The Vegetable song (Beach boys) for Digestion
Good morning starshine (from the musical Hair) for Life cycle of stars
A New England (Kirsty MacColl) for Satellites

However, in a much crueller way, I also like to play 'science songs' which get inside students heads and hopefully helps them remember the ideas.  Most of these are from 1950s or 60s recordings which can be found at 'Singing Science Records' .  They are very dated, but I love them.  At a previous school I included 'E-lec-tric-ity' in the department lesson plans, and you could hear students coming out of their science lessons singing this song.  Great!

Other classics of the genre:
The photosynthesis song by Peter Weatherall
Meet the elements by They Might Be Giants
The elements by Tom Lehrer
Bunsen Burner song by John Otway
Electric Car by They Might Be Giants
Digestion Blues by Joe Crone

Fizzy drinks and Liver disease

Confusing Cause and Correlation.

The Daily Express had a front page story about the Danger of Just Two Fizzy Drinks. It reported work by researchers at a liver unit in Israel who had apparently found that drinking a litre of fizzy drinks or fresh juice were five times more likely to develop non-alcoholic fatty liver disease (NAFLD).

Although the Express story gives some details about the study design, there aren't many. Reading it we don't know how many people took part in the study, if it was a dietary intervention, or just an observational study. We have no information about how long the study continued.

There are a couple of suggestions from the researcher, Dr Nimer Assy, about problems that drinks high in fructose could cause, but these are not backed up by data.

The NHS Behind the Headlines site has, as usual, an excellent breakdown of what was done, and what it all means.

The paper itself is a conference poster report from April 2009. There isn't much to go on in it, so I had a look to see where the other information in the article could have come from. There was no sign of a press release on the news services Science Daily or EurekaAlert. Nothing from the Ziv Medical Centre (where Dr Assy works) itself. Strange.

Eventually I found a link to Israel 21C where there is more detail about the study and quotes from Dr Assy.

Interestingly, when you read the paper, and the interview, you find that the Daily Express have got a few, quite important, details wrong.

Israeli scientists at the Ziv Liver unit in Haifa compared two groups of
volunteers – neither of which was at risk of developing the condition.

When they finished the study they found that 80 per cent of those who had consumed fizzy drinks and fruit juices had fatty liver changes.
But only 17 per cent of the control group – who had not drunk fizzy drinks – developed fatty ­livers.

What isn't clear here, is that there were three groups of people taking part in the test.

• 32 patients with NAFLD who had typical metabolic risk symptoms (such as obesity and diabetes)
• 28 patients with NAFLD who didn't have risk symptoms
• 17 patients without NAFLD

The amount of fat in the liver was measured using ultrasound. At the beginning and end of the six month study the volunteers were asked to keep a 7 day food and drink diary.

What the researchers found was that 70% of the patients with NAFLD drank more than 1/2 litre of soft drinks compared with 20% of the controls.

So, there is a correlation between drinking lots of soft drinks and having NAFLD. Does that mean that drinking lots of soft drinks will cause liver disease?

No, not necessarily. This study can't tell us if it does. Unfortunately, the Daily Express (and to be fair, the Daily Telegraph who also carried the story) didn't realise that.

Abed A, Nseir W, Ali T et al. Soft drink consumption linked with fatty liver independently by metabolic syndrome. Journ of Hepat. April 2009