Don’t worry, it’s just a fast (oxidisation) reaction…

MarvinEvery explosion is “just” a reaction, admittedly one that progresses very quickly (Boom! Kaboom!). Oxidisation is the word used in chemistry to mean “a reaction with oxygen”. Oxidation reactions are essential because they release energy – respiration is an oxidation reaction, as is burning (combustion) and also corrosion. Respiration is good, burning can be good, and corrosion is rarely good. An example of corrosion is iron (Fe) rusting. When Iron combines with oxygen and water, iron oxide is produced:

4 Fe(s) + 3 O2 (g) + 2 H2O (l) → 2 Fe2O3·H2O

RustThe reactants (Iron, Oxygen, and Water) combine chemically to make saturated (·H2O) iron oxide (Fe2O3). Iron oxide has none of the properties that are desirable in alloys of iron – it has low strength, is friable (crumbly) and completely non conductive. We try and prevent corrosion at all times, because it degrades materials. the two most common ways of preventing corrosion are:

  1. Painting: The paint provides a protective layer that keeps the water/ oxygen from coming into contact with the iron. This stops the iron from contacting either water or oxygen, thus preventing the corrosion reaction.
  2. Sacrificial Protection: This works by coating one metal by another. The coating metal must be higher on the activity series than the coated metal. One example of this is coating Iron with Zinc (also called galvanisation). This prevents the coated metal from corroding by causing the more reactive metal to corrode first.

The activity series shows some metals are more active than others – here is a video that shows how reactive (explosive!) some metals can be:


Please note that this video has been faked for the more highly reactive substances!

See you in class!

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14 Comments on “Don’t worry, it’s just a fast (oxidisation) reaction…”

  1. Julian Says:

    Any chance we could get our hands on some potassium and water?

    that would be a awesome prack

  2. Ben Says:

    In the video Dr Tickle mentions that the rubidium is sealed under “Argon atmosphere conditions”. What does this mean?

    Also, I found out that the reason why they couldn’t get a hold of the Francium is because only 30 g (at the most) of it exists in the Earth’s crust.

  3. Rachel Bailes Says:

    I’ve tried to find out why corrugated iron is corrosion resistant, but all I could find was that all Corrugated Iron was galvanised, and also known as galvanised sheeting.

  4. mrgrichting Says:

    Sorry Julian – no potassium and water. We may do a demo of Sodium and water… no promises!

    Ben, Argon is what is called a noble (or inert) gas. It is very unreactive, so it is safe to store rubidium in it. Also, about the rarity of Francium – it is also unstable and decays to be destroyed continuously. Fortunately, it is also created continuously!

    Rachel, I didn’t ask why corrugated iron is corrosion proof – I asked why corrugated iron is used more than sheet iron.

  5. Mark L Says:

    Rachel

    You kind of answered the question i think.
    The corrugated iron is galvanised which means the iron has been coated, most likely to be zinc. This prevents the coated metal (iron) from corroding by causing the more reactive metal, (zinc) to corrode first. This called sacrificial protection, one of the two most common ways of preventing corrosion. This is why corrugated iron is used more than sheet iron. It is way more protected than sheet iron

    Read Unit1.3 in the Science textbook. it will help you understand it more. That’s why i found out about the ways of preventing corrosion.

    Mark
    10M

  6. Rachel Bailes Says:

    I’m not sure that the galvanisation is the reason for corrugated iron being used more than sheet iron. It has several structural advantages over flat/sheet iron; it will not snap as easily – due to the corrugated ripples bending instead of snapping. Perpendicular to the ripples, the iron is very strong and will not bend.

    However, if needed, the iron can be bent parallel to the ripples. Because of these advantages, the corrugated iron was used for simple curved shade structures at the time it was first concieved. It can be used as a barrel roof because of the increased malleability, and if broken can be fixed and reused easily.

    Also, it has been known for its ‘simplicity’ – and how easy it is to install, due to its inexpensiveness and lightness.

  7. Mun Hon Says:

    Yo people and Mr. G.

    Not related to half of what you guys are talking about, but I did find out what Ben found out about the Francium being limited in the world.

    Also, I searched on youtube and there isn’t anything showing Francium in water but there were a couple of explosions and some guy made a song about francium. Wikipedia didn’t say anything about it reacting with water either yet they managed a massive page of stuff. Oh and another reason why they couldn’t get francium is because it’s radioactive which I found out from the internet somewhere.

    Mun Hon
    10M

  8. Mark L Says:

    i didnt think of it that way Rachael.

    Obviously you have done a lot more research than i have.

    mark

  9. Mark L Says:

    hi Mr G

    wats can actually corrode gold?

    mark

  10. mrgrichting Says:

    Hi Mark (&Class)

    The most common thing used to corrode (or more precisely dissolve) gold is Aqua Regia (Latin for the Water of Kings). It is a mixture of concentrated hydrochloric and nitric acid.

    See: http://en.wikipedia.org/wiki/Aqua_regia
    http://jchemed.chem.wisc.edu/JCEsoft/CCA/CCA3/MAIN/AQREGIA/PAGE1.HTM

  11. kim Says:

    Hey Mr. G

    On the activity series, why is the word hydrogen highlighted blue?
    Is it because its a gas?

    Kim

  12. Mark L Says:

    Mr G

    Does any bank in Australia use Aqua Regia to store their gold bullion in?
    Cause i doubt many thieves would have the scientific knowlege to extract it.

    mark

  13. mrgrichting Says:

    Hi Kim,

    I’m not sure why Hydrogen is in blue in that diagram; It could be as you suggest.

    Mark, the only problem with that is that it is exceptionally toxic and even explosive. On top of that, it is a bit difficult to store…

    MrG.

  14. Julian Says:

    Yo all and Mr G,

    this has nothing to do with anything that has been posted

    if anyone finds a site where it shows how to draw periodic elements could you post the site?
    thanks 🙂


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