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February 22, 2010 7:21 PM   Subscribe

What kinds of simple, safe chemical reactions can I do to really wow a group of 6th graders?

I'm working on planning a lesson for a group of 6th graders in an advanced science class I'm student-teaching in. In the actual lesson, they'll be working with calcium chloride, baking soda, phenol red indicator, and a few other things to measure changes in heat during chemical reactions. Despite being in an advanced science class, many of them haven't ever had much of an experience with chemical reactions. For my first lesson, I used a Bill Nye video to introduce the kids to what we were looking at- but this time I really want to do some kind of demonstration. Something past baking soda and vinegar or Alka-seltzer tablets.

The ideal demonstration would:
1. be short (I can do as much advanced set up as needed but the actual demonstration needs to be <5 minutes long)
2. use relatively simple ingredients- we can order some things or obtain others through the university chemistry program but that's not a guarantee. bonus for household items
3. be safe enough to do in a middle school classroom
4. have some kind of wow factor- small explosion, color change
Thanks for any ideas!
posted by kro to Education (33 answers total) 28 users marked this as a favorite
 
I don't know much about chemistry but I was watching this video of a chemical reaction called traffic lights when I saw this question.
posted by joydrop at 7:28 PM on February 22, 2010 [1 favorite]


Magnesium fire. Bright, fast, and it weighs MORE after you burn it.
posted by longsleeves at 7:30 PM on February 22, 2010


This one requires sulfuric acid: Dehydration of sugar with sulfuric acid.

Summary: Sugar turns into a rapidly rising tower of steaming carbon foam.
posted by Salvor Hardin at 7:33 PM on February 22, 2010


One of the cooler things is to mix two solutions. In one you put a small amount of some ferric salt (e.g. ferric sulphate). In the other you put sodium (or potassium, or ammonium) ferrocyanide. You don't need much of either, and the resulting solutions are clear.

But when you mix them the result instantly turns black if the concentrations are sufficient. (You've created "prussian blue".)
posted by Chocolate Pickle at 7:34 PM on February 22, 2010 [1 favorite]


Dry ice, water, soap and a sink and you can have some cool effects.
posted by 6:1 at 7:38 PM on February 22, 2010


Whooo so many good ones.

Genie in a bottle- Strong hydrogen peroxide in a glass bottle. Drop a piece of Mn02 wrapped in tissue paper and watch steam fly out. For extra cheese factor, suspend it in the bottle with a string caught in a stopper. Open the stopper and the "genie" comes out.

Elephant's toothpaste- Again, hydrogen peroxide. Mix some with dish soap and pour into a very tall graduated cylinder. Add KI saturated solution and watch a lot of foam come out. hint- cover benchtop with paper towels to ease cleanup.

Lycopodium powder fireball- Attach a funnel to a foot or so of rubber tubing and light a bunsen burner on a bench. Have kids stand back quite a ways. Pour a few tablespoons of lycopodium powder (I have heard powdered coffee creamer works too ymmv) into the funnel while holding your finger on the other end of the hose. point the funnel over the burner (in the direction you want a big fireball) and blow the powder out. This one is absolutely fantastic. Start with small amounts of powder, I singed my eyelashes off going all in...

Slime is great. There are a ton of variations. I have done polyvinyl alcohol plus borax solution and it works pretty well, but making the alcohol solution takes all day on a hot stir plate.
posted by mcarlson85 at 7:40 PM on February 22, 2010


Elephant toothpaste.
posted by pemberkins at 7:40 PM on February 22, 2010 [1 favorite]


Coffee cup calorimetry is simple and learny. Here are some examples: google
posted by kuujjuarapik at 7:42 PM on February 22, 2010


Dry ice in a sink, water and dish soap and a sink and you can have some cool effects. Your tag makes me think of this commercial, which I thought was cool.
posted by 6:1 at 7:43 PM on February 22, 2010


Slime is great. There are a ton of variations. I have done polyvinyl alcohol plus borax solution and it works pretty well, but making the alcohol solution takes all day on a hot stir plate

We made slime in my sixth grade science class and it was awesome.
posted by sallybrown at 7:56 PM on February 22, 2010


I found the blue bottle reaction fascinating. The solution turns blue when put into motion, returning to transparent when let to rest, and is repeatable. It's a nice example of a reversible reaction and is kind of counterintuitive to people new to chemistry, and thus quite illuminating when understood.
posted by mnemonic at 8:00 PM on February 22, 2010


The dancing gummi bear demonstration.

Don't settle for the tiny little test tube described in that link. My public school chemistry teacher used tongs to carefully lower the gummies into a 1L beaker about 1/10 full of potassium chlorate, then immediately withdrew and covered the top with a lid (with a narrow opening for venting) so we could watch the poor bear rebound off of the glass sides during the reaction. You can dim the classroom lights to better see the sparks and colours. Gummi worms work well too.

It's also a good segue for talking about lab safety, and showing off the goggles, mitts, and other precautions you'll take during the demo.
posted by ceribus peribus at 8:13 PM on February 22, 2010


red cabbage extract changes color in response to pH changes.
posted by LobsterMitten at 8:23 PM on February 22, 2010


Mentos in a 2 liter bottle of soda pop.

Awesome.
posted by SLC Mom at 8:23 PM on February 22, 2010


chocolate pickle: But when you mix them the result instantly turns black if the concentrations are sufficient

Yes! This!! I remember being a 3rd grader and seeing someone do this, and to this day I remember how awesome it was. Also when it turns black a whiff of steam goes up!
posted by Pallas Athena at 9:14 PM on February 22, 2010


I am seconding ceribus peribus's suggestion of a gummi bear dropped into heated potassium chlorate. I saw the so-called "gummi bear experiment" well over ten years ago, and it remains my favorite memory of any science class EVER. My chemistry teacher (who was awesome, and a total goon) hyped up the mysterious gummi bear experiment ALL YEAR. All the in-jokes and buildup did not disappoint. Turn the lights off, make a production out of it, and then do the heck out of the mighty gummi bear experiment. The last step, of course, is to be known as the coolest student teacher ever.
posted by missmary6 at 9:15 PM on February 22, 2010


I don't know if it's easy to do, but the Belousov–Zhabotinsky reaction is really cool. Check it out on YouTube.
posted by sevenyearlurk at 10:16 PM on February 22, 2010


Don't settle for the tiny little test tube described in that link.

I think the test tube is more dramatic, since (if you get the right sized tube), it sounds like the gummy bear is screaming in agony as it reacts. Maybe too traumatizing?

I would go outside and do a thermite demonstration, if you can get the materials. You can set it off with a magnesium strip or the above sugar/potassium chlorate reaction. Get a terra cotta pot from the hardware store (with a drain hole in the bottom), put a piece of paper in the bottom of the pot, then put the pot on a ring stand outside. You may want to put a pile of sand underneath it, but you can pull solid chunks of iron "slag" out of the sand when the reaction's done.
posted by backseatpilot at 11:59 PM on February 22, 2010


I think the test tube is more dramatic, since (if you get the right sized tube), it sounds like the gummy bear is screaming in agony as it reacts.

That's fun too, but you get more of a Tazmanian Devil effect if the gummy has room to whirl around a bit, and you hear the individual snaps and sizzles whenever it touches down. Try it both ways!
posted by ceribus peribus at 12:56 AM on February 23, 2010


Similar to sevenyearlurk's suggest of the BZ reaction is a variation called the Briggs-Rauscher Reaction.

check out this video here to see it in action.
posted by TheOtherGuy at 1:13 AM on February 23, 2010


No chemicals involved, but there's the soda can demonstration. Put water in the bottom of an empty soda can, and heat the can on a hot plate. When the can gets hot enough, use tongs to move it to a clear container of cold water. When heated enough, the can will be crushed (with a pretty load pop) by the change in air pressure inside the can.
posted by _cave at 2:52 AM on February 23, 2010


Corn Starch and Water becomes a strange mixture that has characteristics of liquid and solid. I remember really enjoying messing around with a bowl of the stuff when I was about that age.
posted by clearly at 7:06 AM on February 23, 2010


As someone who taught chemistry to non-scientists for several years, I would recommend that you ABSOLUTELY NOT do explosions, or (jesus f christ) thermite, especially if you yourself are not incredibly experienced with those reactions. Yes, they are showy, but they are also a really fucking good way to hurt yourself or someone else, or to encourage impressionable kids to hurt themselves. I cannot stress this strongly enough! Please, use your common sense.

There are lots of other great suggestions here. Also--Separations are be pretty cool and are very important for chemists (to get pure substances out of mixtures). Google around for stuff on paper towel chromatography. Super-simple, all you need is a white paper towel (or coffee filter, or similar) and some solvent (water will do, or you can experiment with isopropyl alcohol.)

I find that the black Vis-a-Vis brand, water-soluble/washable felt-tip marker gives a really lovely range of colors--red, yellow, turquoise--in with the black pigment. It's pretty simple to set up a real experiment here--pick a variety of black markers, washable and permanent; pick a few different solvents, including water, vinegar, isopropyl alcohol; see how different markers separate or not depending on the solvent. Cool stuff.
posted by Sublimity at 7:32 AM on February 23, 2010


When heated enough, the can will be crushed (with a pretty load pop) by the change in air pressure inside the can.

I'm missing something - how do you seal the can after letting the steam escape?
posted by roystgnr at 7:37 AM on February 23, 2010


Not nearly as showy, but something the kids can do themselves:

Put a glass of Sprite on a tray.
Sprinkle black pepper to cover the entire surface.
Once that is fairly sturdy, pour salt into the center of the surface. When enough salt accumulates to be heavy enough to break the surface, it plunges into the Sprite and the whole thing fizzes over onto the tray.

Do they still sell soda in school cafeterias? The cafeteria ladies will hate you
posted by CathyG at 8:01 AM on February 23, 2010


Sodium Acetate--in a super saturated solution, it turns into crystals by just touching it. Also it's an exothermic reaction. Hand warmers are filled with it.

Seconding dry ice, warm water and soap. Check out large grocery stores, many have started carrying dry ice for construction workers' lunches. They might think they're too cool for this, but food coloring always helps.

Hydrochloric acid solution (easy to find at a hardware store, it's used to clean concrete) and scratched up pennies--zinc--make hydrogen gas. US pennies minted after 1986 are all zinc, except for a copper plating. Use a bunch of scratched pennies to make the reaction faster. Set the reaction up in a flask, capture the hydrogen with a balloon around the mouth of the flask. Talk about the Hindenburg while the ballon expands. Then tie the balloon up and tie it to a weighted string. Fasten a match to a pole, light match and pop the balloon.

They will remember this FOREVER. Make sure the kids in the front row have goggles on or that they don't care about their eyebrows. (I kid, I kid.)

Youtube has some great examples.
posted by montaigneisright at 8:22 AM on February 23, 2010


When heated enough, the can will be crushed (with a pretty load pop) by the change in air pressure inside the can.

I'm missing something - how do you seal the can after letting the steam escape?


You don't seal the can.
posted by _cave at 8:36 AM on February 23, 2010


Don't pay to much attention to video guy's explanation, though.
posted by _cave at 8:37 AM on February 23, 2010


And that's "loud pop". Geez.
posted by _cave at 8:38 AM on February 23, 2010


Feed them sugar.
posted by eccnineten at 9:44 AM on February 23, 2010 [1 favorite]


No worries, Sublimity, we have the safety aspect well covered...I'm still an education major, science nerdiness aside. Some of these things, some of which I've seen before (like the thermite reaction) are awesome, but I'd be more afraid of hurting myself than them. Also, my Chem I professor did the hydrogen gas balloon thing and it was possibly the most terrifying thing I'd ever seen- I don't deal well with loud noises.

clearly, we actually looked at Oobleck (cornstarch and water) for our first lesson looking at non-Newtonian fluids- messy, but a lot of fun.

I'm leaning towards the traffic light or prussian blue demonstrations, or elephant toothpaste- that same chem professor did elephant toothpaste and I thought it was cool as a 20 year old college student, it would be a hit with these kids.

Thanks for all the ideas! I think I'm getting more enjoyment watching/looking at all the links than the kids will.
posted by kro at 7:47 PM on February 23, 2010


The Electric Pickle demo.

It glows! It makes small popping noises! It smells funny! It demonstrates electron transfer through ionization and sodium's emission spectrum!

And, um, it's one of the best opportunities I've ever found for getting to do Frankenstein/Igor impressions. You've got the pickle with little bolts out its ends, the electricity, the dramatic switch-throwing...and as long as nobody touches the live pickle or wires, it's perfectly safe. If you want to tie it into your lesson plan more directly, you could even take the pickle's temperature before and after (starting at room temperature, natch) to illustrate energy transformation.
posted by VelveteenBabbitt at 11:33 PM on February 23, 2010


Well I see that you don't want to do a hydrogen explosion but if you change your mind another creative way to do it is to use simple hydrolysis with water and a 9 volt battery. For electrodes you can either use two carbon rods (which you can get by taking apart non-alkaline/dry cell batteries) or gold plated electrical connectors. Just put them both in the water and hook up the battery and you should see bubbles. Put a balloon over the water or otherwise capture the hydrogen. The gas is produced slowly enough that if you don't want a huge boom you can stop it before much hydrogen has been collected and it will me more of a pop.
posted by Rhomboid at 2:57 AM on February 24, 2010


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