Monday, 4 February 2013

She Blinded Me With Science


It's really not!  The reason i chant that is that because this is not a wiki, it's OK for me to put educational materials on here without worrying about why nobody else is doing anything.  The video will be near the bottom - as i type, it rendereth yet.  In the meantime, here are some "interesting" diagrams.  Bear with me and Uncle Markie will 'splane:

OK, so there's this thing called the reactivity series, which sadly probably falls into the category of Lies To Children, but whatever, it's on the GCSE syllabus so i have to include it and after all it is kind of useful.  The video will explain most of it, but the colour scheme i've chosen works like this.  The most reactive elements included in the scheme are outlined in violet, the next most in indigo and so on, ending with a sort of bricky colour with the noble metals.

You have probably noticed that not all the elements are included.  This is because it's impractical for introductory chemistry syllabi (gr?) to cover the likes of yttrium and polonium.  However, clearly there are some elements on there which are widely available, so go figure.

This video is over eleven minutes long, which is well over twice the recommended length of four.  Unfortunately, i'm just going to have to do it that way because there's probably no way i can make this shorter unless i break it into two videos, which will clog up the stream and annoy people.

In fact, i can see there may be a need for more than one channel.

This video is also very talky and not very demonstrative although it has a lead pipe in it, which i ripped off the outside toilet wall.  One thing i'm not sure about is the change in the colour scheme halfway through the video.  The early part of the video has the names of the elements coloured either by their appearance as pure metals or by the appearance of their flames, but the later part colours them spectrally, with violet as the most reactive and reddish as the least.  This is probably a bit confusing.  Also, the height of the names in the early part of the video corresponds to their level of reactivity.  As usual, i talk around the subject as well as directly about it because that's how i think home ed works best for most children.

I'm a bit too attached to this being read.  Sorry about that.

Anyway, vid goes here:

 The reactivity series is used in introductory chemistry courses such as the GCSE syllabus to rank the metallic elements in order of reactivity.  Arranged from the most to the least reactive, metals near the start of the list are more susceptible to corrosion, stronger reducing agents, more likely to give up electrons to form positive ions and need more energy to be extracted from their ores.

The most reactive metals in the series are, in order:  caesium, rubidium, potassium, sodium, lithium, barium, strontium and calcium.  These react with water and can be extracted using electrolysis.  It's noticeable also that none of the metals on this list is familiar in everyday life.  This is because they are usually found only in combination, hence the examples i give.  All of these metals are also in the first two columns of the periodic table and the less reactive elements are lighter.

The next three metals are quite distinct.  Magnesium reacts with acids but not strongly with water and can be extracted by electrolysis.  It oxidises readily, as can be seen in magnesium flares.

Aluminium is a metal which was formerly more valuable than gold.  The invention of the Hall-Heroult process in the late nineteenth century made it much cheaper, but much aluminium is still found in common rocks and soil, but is still uneconomical to extract.  Aluminium reacts with acids and as a result it is dangerous to use aluminium cooking utensils to cook acidic food such as tomatoes and vinegar, since aluminium has been implicated in Alzheimers disease, although this may be more to do with the blood-brain barrier.

The third of the more individual metals is titanium, which is effectively still almost a precious metal.  It reacts with concentrated mineral acids such as sulphuric acid, and is extracted using the Kroll Process, which is a process specific to the extraction of titanium and the similar metal zirconium.

Less reactive than these are manganese (there's a mistake in the video at this point - i accidentally said "magnesium"), zinc, chromium, iron, cadmium, cobalt, nickel, tin and lead.  These react with acids and can be smelted with coke.  They are often found in nature as sulphides or oxides and the carbon in coke combines more readily with them than they do with the metals.

Finally, the metals antimony, bismuth, copper, mercury, silver, gold and platinum, which are either found naturally in an almost pure state or can be extracted by the use of heat or physically.

The whole idea of the reactivity series is apparently deprecated in higher academic chemistry.

For the three "cards" at the end of the video, please see here: