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I actually have to perform an experiment for my school project, and since chemistry is a subject which has the ability to show some pretty good results, I'm not able to think about a project which could leave everyone impressed. I'm thinking about the elephant toothpaste thing, but I don't think it's that good. Any recommendations?

EDIT: I actually want some decent experiments which have a high level of explanation and makes people think I'm a genius and has a great visual impact. The ideas are good, and introducing the twists makes it look better, but I would prefer an experiment which has a higher level of explanation.

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closed as too broad by Michiel, jonsca May 12 at 6:11

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

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By "simplest possible," what do you mean? Small number of steps? "Safe" chemicals? Simple apparatus? This would help narrow down some options. –  trb456 May 3 at 15:32
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This is a bit too broad. You have gotten some answers, but it would be better to narrow it down a bit as @trb456 has mentioned. –  jonsca May 3 at 16:37
    
A chemistry teacher back in secondary school used to demonstrate a reaction involving aluminum powder and an oxidizing agent (a white powder; he never told us what it was). Mix those thoroughly and set on fire. The flash is extremely bright. Needless to say, this doesn't really qualify as safe. ;) –  ntoskrnl May 4 at 9:51
    
Actually my chemistry teacher has to bring the chemicals (if available) so by simplest possible actually means easy to get and a little bit easy to explain (the explain part doesn't matter as much). –  Rohinb97 May 5 at 11:04
    
might be worth a look: chemistry.stackexchange.com/questions/10465/… –  Martin May 5 at 14:49
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6 Answers 6

As others have commented, it would help a lot if you were a bit more specific about what kinds of experiments you'd be comfortable with, and where and to what audience you're performing it.

For instance, I've always found the ammonium dichromate volcano experiment pretty nice and impressive, but it does involve fire and produce noxious (and carcinogenic) chemical smoke, both of which can be dangerous if proper precautions are not taken. Also, you can't just buy ammonium dichromate from the grocery store, although your chemistry teacher may well have (or be able to obtain) some.

On the other hand, if you'd prefer something easy, safe and doable using common household materials, here's a simple "magic trick" based on natural pH indicator dyes that I remember impressing my 9-year-old classmates (and at least some of their parents) with a long time ago:

You need:

  • one red cabbage (you don't actually need a whole cabbage, but it's pretty cheap, and you can always eat the rest)
  • a few teaspoons of clear vinegar
  • a few teaspoons of baking soda
  • a glass bottle, jug, pitcher or similar transparent serving container
  • two drinking glasses

Preparation:

Chop up some red cabbage leaves and boil them in a few cups of water to leach out the anthocyanin dye from the cabbage. Once the water has turned a deep shade of purple, strain out the leaves and let the water cool. (If the water turns reddish or bluish, add some soda or vinegar to adjust the hue.) You can prepare the "cabbage juice" a few days in advance, and store it in the fridge until needed.

Before the experiment, pour out about half a glass of the cabbage juice, and slowly add just enough vinegar to turn it clearly red. Note the amount of vinegar needed for this. Then slowly add enough baking soda to turn it purple again, also noting the amount. Just to check, double the amount of soda and observe the juice turning blue.

To set up the experiment, pour the previously noted amount of vinegar into one glass, and the previously noted amount of baking soda (dissolved in a small amount of water) into the other. The glasses should still look empty from a distance. Fill the bottle / pitcher with a glass or two of the cabbage juice.

Performance:

Show the audience the bottle / pitcher of juice, explaining that it's magic purple fruit juice made by mixing red and blue juice. Explain that the reason it's magic is that you can pour out the red and the blue juice separately, which you demonstrate by pouring half a glass of juice into each of the glasses. If you measured the correct amount of vinegar and soda into the glasses, the juice in them should turn red and blue respectively. You can then pour the juice from one glass into the other, turning it purple again.

Now, at this point, since you're doing this as part of a chemistry demonstration, it should be obvious to the audience that there's a chemical reaction involved. If they're familiar with pH indicators from prior lessons, they may even guess what kind of chemistry is involved. That's not really what makes this trick impressive.

The impressive bit, rather, is that at this point you can do something you'd normally never do with a chemistry experiment — you can casually pick up the glass of "magic juice" and drink it. It may not taste particularly good, but, since the only things that went into it were baking soda, vinegar and red cabbage, it's perfectly safe to consume.

Do remember to explain what the juice really is, before somebody goes and calls an ambulance. This can also serve as a good introduction for a further discussion of the kinds of "everyday chemistry" involved in cooking and other household activities.

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If you plan to drink it, make sure you use clean drinking glasses or water bottles. Don't drink from equipment from a lab, including but not limited to beakers and flasks. Not even if it looks clean. (I know it's implied, but better to make it extremely clear, yea?) –  Bob May 4 at 10:28
    
@Bob. Good point, and certainly worth stressing. You don't know where that lab beaker's been, or what's been in it. Don't even think about drinking from it. Use a proper drinking glass. –  Ilmari Karonen May 4 at 12:32
    
The pH thing is too.....easy? It's just that it isn't too good to show, but the drinking bit might go a bit extreme. The volcano idea is good. –  Rohinb97 May 5 at 11:05
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http://en.wikipedia.org/wiki/Bassam_Shakhashiri
http://www.amazon.com/Chemical-Demonstrations-Handbook-Teachers-Chemistry/dp/0299088901
Volumes 1 through 5. Visit a university library.

http://en.wikipedia.org/wiki/Belousov%E2%80%93Zhabotinsky_reaction
http://www.ux.uis.no/~ruoff/BZ_Phenomenology.html
http://www1.chem.leeds.ac.uk//People/SKS/esf_reactor/Hegedus.pdf
http://www.jhu.edu/chem/fairbr/teach/Past/FourierTransform-Lab1.pdf
http://www.youtube.com/watch?v=3JAqrRnKFHo
Centers set off with dust motes, or the hot tip of a paper clip.

I like the Traffic Light. It is a Belousov–Zhabotinsky reaction chemical oscillator with cerium and ferroin so that clear and yellow plus red and blue give red and green. NO CHLORIDE! A beaker of the stuff fizzes, and the mist is choking. Cover the beaker with a round of filter paper. The BZ reaction in a Petri dish is pretty good, too - but slow.

http://www.youtube.com/watch?v=8TPnns-5UxA
Very Bad Ideas. Don't do it. (Ferrofluids are OK and easy to make, water- or oil-based, but how will you explain them?)

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This is a simple demonstration of the blue bottle solution. It will change from colorless to blue when shaken and upon sitting for a few minutes, it will become colorless again (or is that backwards).

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Could you at least summarize what's at the link in the answer? You've been around, you know better ;) –  jonsca May 3 at 16:36
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Methylene Blue's large molar absorptivity, 89,000/M-cm at 655 nm, makes the solution blue with a few dust specks. It is slowly and reversibly reduced to colorless leuco-methylene blue in alkaline aqueous glucose. That is in turn rapidly oxidized by atmospheric oxygen, aac.asm.org/content/52/1/183/F1.large.jpg Having a public school student explain it will be interesting. –  Uncle Al May 3 at 23:23
    
I used it to introduce redox reactions and to demonstrate its usefulness, there was this family that had blue skin. google.com/… –  LDC3 May 3 at 23:32
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I always enjoy a good ketchup bomb.

Ketchup contains acetic acid, although in small amounts. If you add some baking soda (NaHCO3), and shake hard to mix the chemicals, the bicarbonate will decompose to carbon dioxide. This gas will build up inside the bottle, and the pressure increases. Eventually you can open the bottle, and shoot ketchup several meters!

To speed up the reaction, you can add a little hot water to the ketchup bottle. This makes the ketchup "more liquid", and the hot water also speeds up the kinetics.

Prank: Mix ketchup and baking soda in an empty shampoo bottle, and give someone quite a surprise in the shower.

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THAT is so goddamn evil.... –  Rohinb97 May 5 at 11:02
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For my money, the electrolysis of water is a great experiment. People with little chemistry knowledge at least know that water is $\ce{H2O}$. In this experiment, you can show that there is indeed twice the amount of one of the gases, and neither gas is "air", given that one burns and the other strongly supports combustion (reignite glowing splint). You can do this with 2 test tubes, a beaker, and a 9 volt battery (careful!), so it's not too bad in terms of apparatus. You could do a little lecture while the electrolysis is underway.

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For added awesome, use a single plastic bag instead of two test tubes, and light the resulting collection of gasses -- preferably with a ten-foot pole. –  Mark May 3 at 20:31
    
Actually, I've seen it suggested that you run the electrolysis half way, then switch the test tubes for the other half, and carefully ignite the contents, knowing that this will be close to the explosive mix. So the explosion is loud, but it can be safe in small quantities. –  trb456 May 3 at 21:27
    
I wouldn't. Maybe you'll get a directional explosion from that, but maybe you'll get shrapnel flying all over the place. –  Mark May 3 at 22:25
    
That is too a bit easy, and I have personally tried it myself a lot of times. But the plastic bag idea makes it fun. –  Rohinb97 May 5 at 11:08
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How To Make Invisible Ink - Baking Soda is a pretty cool and easy experiment.

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While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes. –  tschoppi May 3 at 16:30
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