The Material World class 3: All matter is made of particles

I shuffled classes round a bit this week so that both groups were covering the same material. It helped with preparation and also gives me a little longer to plan our ‘materials processing’ class for KS2.

We started off by looking at a deflated balloon from last week and discussed the gas escaping through minute holes in the balloon. Even with our magnifying glasses we could not see the holes.

Image from simplystatedbusiness.com

We took several other types of material (wood, clay, sandstone, sugar, salt, sand) and drew what we could see with the naked eye and what we could see with a magnifying glass. This is in the syllabus! But most of the children didn’t really enjoy this activity, and perhaps didn’t quite understand what I was asking for. Next time I’ll probably do my own drawings beforehand as an example. Also, I could have provided a range of more interesting pieces of material with details that show up when magnified, e.g. fabric, a toothbrush etc.

Our printer is dodgy but another idea I had was to print out various pictures of things that have been magnified and see if the children could guess what they were.

If your children are interested there’s a free iOS app called Zoom! that does just this, and might help with their spelling too.

Screenshot from Zoom! iOS app

I then asked them to choose one of the materials provided and see if they could get it down to the smallest piece possible. Those who chose clay had the most fun, as they ended up dissolving it into water to get a milky-coloured suspension. I provided a pestle and mortar to grind up the crystals. But I think in another class I would provide safety glasses and hammers so they could have a really good time trying to crush the crystals or rocks.

We talked about how all matter is made of particles. In the older group, one of the children was talking about atoms and subatomic particles and I tried to get them to think of what the smallest particle would be that still had the characteristics of the material,

e.g. what is the smallest piece of wood that still has the same characteristics as a large piece of wood?

Or what is the smallest piece of sugar that still has the same characteristics as a larger crystal?

Wood is made up of plant cells and sugar is made up of molecules. Yes, if we go down to the subatomic level we are looking at the most basic building blocks, but we lose the complexity and specific detail of the larger levels. (I suppose I am trying to steer them away from the reductionist approach that says that all biology is just chemistry, all chemistry is just physics and all physics is just maths. See xkcd comic strip Purity about the very subject.) We can’t even say that one plant cell is ‘wood’ or one molecule of sucrose has the same properties as a crystal. At the very least, you have to have a group of plant cells or a certain number of unit cells in a crystal.

Electron micrograph of wood, probably white oak. Taken from The Word on Wood blog, linked to below.
A model of one sugar molecule. Taken from the Exploratorium website http://www.exploratorium.edu
Solid-state structure of sucrose. Taken from online MolArch+ documentation on the http://csi.chemie.tu-darmstadt.de/ website

I am not sure how much of this went in but, as usual, I hope that if they meet these concepts later on it will spark some memories and perhaps prompt deeper thoughts.

All groups finished off by looking at electron micrographs of the materials we had been studying. Here are the links, and some of the pictures:

Sea Salt http://pwatlas.mt.umist.ac.uk/internetmicroscope/micrographs/crystals/sea-salt.html
Sand http://www.inspirationgreen.com/magnified-grains-of-sand.html

Wood  http://www.woodbywy.com/2013/04/23/micrographs-show-wood-like-youve-never-seen-it-before/

Metal   https://www.youtube.com/watch?v=gO5gPdJxe_o

http://pwatlas.mt.umist.ac.uk/internetmicroscope/micrographs/microstructures/more-metals/steel/steel-micrographs.html

Clay    http://ceramicsweb.org/micrographs.html

Rocks    http://www.earth.ox.ac.uk/~oesis/micro/

If your children want to understand how a microscope works, there is a good, clear explanation on ExplainThatStuff.com. There’s more detail on microscopemaster.com.

MicrobeHunter.com has an article about electron microscopy vs light microscopy.

And finally, the Telegraph magazine has some great micrographs of our food seen close-up.

Close-up of a broccoli floret. From telegraph.co.uk
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