[jeph82]

Hello, I am trying to come up with a fairly simple classroom-style chemistry experiment to demonstrate the basic principle of how molecules bond. The idea behind carbon capture from air (a possible solution to global warming) is that wind blows across a surface coated with sodium hydroxide (NaOH), and the NA ions bond with the carbon (acid-base reaction) making sodium carbonate, which can then be stored safely away. We are trying to come up with a simple experiment to demonstrate this principle, basically, how ions bond, how molecules attract. I'm wondering if anyone might be able to suggest any classic chemistry experiments that might demonstrate this principle? I've looked into baking soda volcanoes, and mentos/diet coke reactions, but neither seem quite right. It would be nice if the experiment involved carbon dioxide, but that's not too important. The main idea is to demonstrate how molecules bond!

[enahs]

The concept behind the CO2 capture scheme you mentioned seems fundamentally flawed to me on many many levels.

But anyway.


The first thing that comes to my mind to demonstrate the possibility of CO2 capture would be a simple acid base solutions.

Any will work:
http://en.wikipedia.org/wiki/Acid-base_titration
With a nice pretty indicator. Get the indicator to just turn color do to basic solution, and then blow into the solution through a straw (blow out CO2), or hook a car exhaust up, drop a piece of dry ice in, whatever, and watch the color change.

You can actually put multipule indicators and get a rainbow of color changes in one.
Here is a video of the kind of thing in general concept I am talking about (not a rainbow in one though):
http://www.metacafe.com/watch/714691/chemistry_experiments_colour_changing_by_dry_ice/

Again, you do not have to use dry ice, any form of CO2 will work.
Because of the following:
http://en.wikipedia.org/wiki/Carbonic_acid



Another good one with CO2 would be to take a block of dry ice (or maybe create an environment of nothing but CO2, not sure if that would work),  drill a hole in it, fill it with strips of Magnesium, light the magnesium strips and put another block of dry ice on top.  The "burning" of the magnesium will produce a bright white light, easily seen through the dry ice, and in the end you are left with:
CO2 + 2 Mg  →   2 MgO + C

There are lots of others. You really need to be more specific I think, or do some research and see what kind of thing you are interested in.

Sites with lots of classic chemistry demonstrations:
http://www.cci.ethz.ch/en/exchoice.html
http://chemed.chem.purdue.edu/demos/Demosheet_index.html




Anyway, this thread should probably be moved to citizen chemists or chem education.

[jeph82]

thanks enahs, you're very helpful! I like your ideas, especially using breath as a reactant.

i'd be very curious to learn what you believe fundamentally flawed about CO2 capture from air. The goal by 2050 would be to have fields of these devices, each the size of a cargo container, and each taking in 1 ton of CO2 a day. The carbon could be reacted with magnesium silicate to form carbonate rock, then stored. The current technology is too expensive and uses too much energy, but there are very motivated people working on it!

[enahs]

CO2 is produced by so many chemical reaction because it is a highly stable and relatively low energy molecule.

Most reactions with CO2 requires energy. That is, you have to input energy to make the reaction occur. This means that in order to sequester the CO2 you must use excess energy in doing so, thus producing more CO2.


Also, the amount of CO2 produced is incredibly large (despite it still being minor minor % of the atmosphere). The amount of material of any kind to do this job will be very large. You are talking about expending massive amount of energy just to get this material, producing more CO2 then you would be otherwise.


It has nothing to do with if it is chemically or physically possibly, only practical and will not in the end waste more energy and produce more CO2 then you remove.


The best option I have heard so far is various types of algae and fungi that live off of CO2, that is the CO2 is what they need to reproduce. With possible genetic modification, or whatever that is called in the plant-type kingdom, making that process more efficient. That way you do not have to waste energy getting more material, the algae or fungi reproduces on its own with CO2, sunlight and water.


The wasting of fossil fuels is not a chemical or physical problem. Things can be done by science to improve the efficiency of all those processes and reduce waste; and I am not saying research should stop in those areas, by all means, research away. But ultimately the wasting of fossil fuels are primarily for economical and social reasons as well as political; not scientific.