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I'm wanting to volunteer at some of our local children centers, and do some experiments to interest them in Science/Chemistry. One cool, flashy experiment is to light my hand on fire - and not have to go to the hospital after.

The general scheme I've found for it (I've not tried it - and the instructions aren't .edu or other '95% correct' sites, so if you know of any corrections for this please chime in) is:

50 - 50 EtOH and Water, plus a small amount of salt for color. Dip your hands in, light them on fire, the EtOH burns coldly enough that the water doesn't evaporate and your hand stays safe and insulated.

Of course, I'll test it on small scale on paper in lab first.

However, I'm initially hesitant to play with fire around children. For obvious reasons.

Does anyone have anything similarly flashy or attention grabbing that they've used for a similar purpose with children? Obtaining restricted materials isn't an issue, but low-cost is preferable.

Note: I know this stackexchange frowns upon questions that don't have a specific answer, with the rules stating that discussion type questions are non-preferred - but this question isn't for the meta site, and I trust this community of educated scientists to have better advice on experiment safety than say, the educator stackexchange, so forgive me if this doesn't fit the general site mold.

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    $\begingroup$ I would advise against doing this demonstration altogether, especially around young children, simply because some of them might think it is a good idea to try it out for themselves. $\endgroup$ – getafix Sep 25 '16 at 2:13
  • $\begingroup$ Yes I agree. I quite dislike the idea @getafix, its maybe a good party trick but thats it. $\endgroup$ – MadisonCooper Sep 25 '16 at 2:14
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    $\begingroup$ There are many, many experiments with a "wow" factor out there that you can use, and require more adult-like skills to acquire materials (like, ordering stuff on the Internet with a credit card) than your audience will possess. One of them is the "wine into water" trick (Google it). Another is a demonstration of the Tyndall effect (see this, for instance). The list goes on and on. I suggest you choose experiments where (1) the materials are not easy to obtain; or (2) the materials will, upon reacting, yield something that's not toxic/harmful/etc. $\endgroup$ – Todd Minehardt Sep 25 '16 at 2:33
  • $\begingroup$ (a) luminol expt looks good as you drop in reactants and get flashes of light, (b) fluorescent dyes with uv lamp, can quench away with iodide. (c) iodine clock, (d) far more adventurous :H2/Cl2 light initiated explosion in a plastic pop bottle. Use a security lamp+ screen. v loud bang, rubber bung in bottle hits ceiling (keep in dark before hand)(e) H2/air explosion + match, H2 from cylinder enters by rubber tube into bottom of old coffee tin. Lid with hole spins off with bang after H2 turned off and H2/O2 left burning in air. Done both of these many times but need proper lab for prep. $\endgroup$ – porphyrin Sep 26 '16 at 16:08
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To talk to kids about chemistry I don't think you just need some exotic experiments.

I visited the Sterling Hill Mining Museum and one of founders had a neat gimmick that got kids attention. He asked them to name some product that had nothing to do with mining. He'd then rattle off a number of things that are mined to make that product. So for a truck the oil and gas are from an oil well. The steel comes from an iron mine and the copper in the electrical wires comes from a copper mine. So have the kids try to name a product that doesn't use chemistry.

Another thing that has always bugged me is the perception of the general public about "chemicals." It seems that the public believes that only things created in some chemical processing plant are chemicals. Well table salt is a chemical. Sugar is a chemical. A strawberry is a bag of water with a zillion chemicals in it. Take a vitamin tablet? The tablet is full of chemicals that our bodies need. Our bodies run on chemistry. So chemicals are all around us.

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    $\begingroup$ Heck, even water is a chemical. $\endgroup$ – Pritt Balagopal May 13 '17 at 15:17
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A lot will depend on the age group of your audience. By "children centers", I'm getting the impression this is pre-school age kids, or at least young kids under 10. You need to set your content to match your audience. Their attention will be grabbed by very simple things, if done well. Everything is new to this age group, so there is no need to impress young minds with whirling-flames-of-death type stuff. They will be equally impressed with bicarb+vinegar volcanoes, especially if you throw in a generous dollop of washing detergent and food dye to make colourful bubbles. Some general things to consider:

  • you have to set extremely high standards of safety. You're not running a magician's festival. That means safety glasses and clean lab coats for all 'experiments'. Young minds will be easily impressioned by the way you do things, not just what you do.
  • Very safe experiments. Stuff you find in the kitchen is usually about as hazardous as you want to get with chemicals. Remember, it is all new to them, so that's ok.
  • Kids will want to touch and get involved and try to repeat what they see. Where possible, design an experiment that they can participate in. It will be a much more memorable experience if they get to 'do' rather than 'see'. At least think about getting one helper (they will love having to put on safety glasses and a labcoat) to add some drops of vinegar to your bicarb volcano, for instance.

That said, here are some examples of age-appropriate experiments/demonstrations to consider:

  • bicarb/vinegar volanco. Works well with several drops of food dye and washing detergent so you create colourful bubbles. (http://www.preschoolinspirations.com/2014/05/28/easy-baking-soda-and-vinegar-volcano-eruption-for-kids/)
  • pH indicator from red cabbage. Most kids won't have met a red cabbage before, I bet. (http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm) This works really well done on a large scale, and allows helpers to pour indicator into your solutions of general household acid/base stuff.
  • invisible ink with lemon juice or milk or some pre-prepared ones using phenolphthalein/bicarb. Washing detergent whitening agents under a black light work great also. One thing I have done successfully with 7-10 year olds is the place some large cardboard sheets around the room that I have drawn large pictures using clothes whitening agents (check they glow under black light first). They are there all the time you are talking and doing other things, and then when you turn off the lights, and turn on the black light....oooh aaah. Scorpions glow under black light also (we find them all around where we live, so are easy to source).
  • coke-mentos fountain is another old favourite that is great for older kids. This is one that is all about nucleation,so we experiment with different types of materials and drinks. Rough sandstone and iron slag works best in normal coke, but if done in the dark, tonic water under a black light gives a great effect. (messy though)
  • static electricity is another great one. Bend water and make the teacher's hair stand on end.
  • making a rubber egg from a normal egg soaked in vinegar. This is a 'here's one we prepared 3 days ago' experiment.
  • clean an old coin (or half a coin is better) in coke. Again this takes a while, so set it up at the start of your session and come back to it.
  • there are some great ideas off this webiste that I have used before (http://www.csiro.au/en/Education/DIY-science/Chemistry). The cornflour slime is great, and kids can have a go for themselves, and don;t care when they get the ratios wrong.
  • Anything with magnets...(perhaps not chemistry though)
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  • $\begingroup$ +1. Supersaturated sodium acetate is another good one to go on the list. $\endgroup$ – orthocresol Sep 27 '16 at 6:07
  • $\begingroup$ I very much agree with the safety focus. I think the experimenter should specifically mention safety. For young kids relate it to safety in the kitchen which would be familiar. $\endgroup$ – MaxW Sep 27 '16 at 14:54
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1) Know your surroundings. Do you have running water? What can you dispose of onsite, either in a sink or trash? Will you have a cart? Where will the demo materials go when they are not being use? How well will the audience be able to see the demo? How loud can you be? Is ventilation an issue?

2) Mentally and physically rehearse and troubleshoot logistics. A demo might seem great at home or on paper, but when you do it, or mentally rehearse it while visualizing your audience and surroundings you may realize that there are logistical issues that you didn't think of. They can be as simple as not having a place to set something. REALLY rehearse onsite if possible. Trying to perform steps of a demo and at the same time to teach requires practice.

3) Proceed slowly and thoughfully. It will seem slower to you than to the audience. Slow down to do "little" things like put caps on bottles before proceeding with the next step of the demo, or move liquid containing vessels to where they can't be knocked over.

4) Have a fairly simple, straightforward learning objective for each demo. Have the kids repeat it and explain what it means. Don't try to overload a given demo with trivial points that may detract from the ability of your target audience to learn a key point. That doesn't mean that you can't make 2-3 points during a demo. For primary grades you might want 1-2 key points.

5) Have a method of illustrating things on a molecular level. You should either have a white board, projector OR models that you can move. Models can be as simple as large circles of construction paper or card stock with letters written on them. For example, you can have a circle covered in aluminum foil to represent aluminum or other metal atoms, and others to represent two atoms in a compound. Neon colors work well.

You are responsible for assessing the safety and feasibility of the demo. Generally, demos with flammables, corrosives, and the potential for pressure to build up may REQUIRE safety glasses, shields, ventilation, eyewashes. You also need to know if you will be producing a waste material that requires special disposal.

Examples:

I personally am comfortable making hydrogen gas from calcium metal and ice water in a thick walled jar, but you end up with a vat of strong base.

I am OK with filling a balloon with $\ce{H2}$ in certain settings, and igniting it, but it will be loud, and could trip a fire alarm, and might violate local ordinances, and there are subtle issues with the procedure that you only appreciate with experience. The whoosh bottle with alcohol is similar though you need to decide if you want to use materials that your audience may have easy access to.

You can combine Lead Nitrate with Sodium Iodide to make a bright yellow precipitate, but you now have lead based paint to dispose of.

Here are some possible demos.

  • Make a large density column in a cylindrical vase using corn syrup, water, oil and alcohol. You can add food coloring to the water, corn syrup and alcohol (red, green, blue). You can also have things for kids to come up and drop into it and talk about how far down they will stop.

  • Use hydrogen peroxide and yeast enzymes to make oxygen gas in an inverted, submerged bottle. Then place a taper inside and see how bright it gets. You can talk about how enzymes can break apart hydrogen peroxide, or how the candle burns faster with more oxygen, and that the air we breath is not mostly oxygen.

  • Solutions of $\ce{KSCN (clear) + FeCl3 (yellow)}$ will combine to make a blood red/brown product. Color change can be a sign of a chemical reaction. You can dip a strip of paper towel in to pull up some of the solution.

  • PVA will polymerize in the presence of sodium borate to make slime.

  • $\ce{CuCl2}$ can be dissolved to make a solution which will react with aluminum cans or foil. You can show that salts contain metals as the copper gets replaced by the aluminum. $\ce{CuCl2}$ is caustic and toxic but you will end up with aluminum chloride in the solution. (There are health concerns with aluminum chloride. You could use zinc.)

  • If you drop alka seltzer in vinegar with a pH indicator you can watch it neutralize acid. Again, a large vase may be cheapest, but will crack easily if you tip it over and also produce sharper shards than lab grade glassware.

  • You can show flame colors from salts with different metals. https://www.youtube.com/watch?v=jJvS4uc4TbU It looks like he may have dissolved salts in a mostly alcohol and lit the alcohol. This method would not require a gas burner.

  • You can also have kids to paper chromatography using coffee filters and magic markers. All they need is a filter, a few markers and a cup of water.

  • There are chemical hand warmer reactions where kids can mix chemicals in a plastic bag and feel it get warmer.

  • Something as simple as having 4 solutions is large flasks, 1 M HCl, vinegar, water and 1 M NaOH and placing a few drops of universal indicator in each one.

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Firstly let me say that what you're suggesting is a horrible idea. The fact that you understand the kids will try to copy you makes this even worse. Do not do it!

  • The most impressive chemistry demonstration I've ever seen (in a classroom setting) was one in which a ~15L round bottom flask was used to demonstrate the luminol-peroxide reaction. It may not be as impressive if the light level can't be sufficiently low.

  • There are several reactions in which a solution goes through a series of color changes.

  • The production of nylon at the interface of two liquids is pretty impressive for older grade/middle schoolers.

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