From: Lee Latimer <lhlatimer**At_Symbol_Here**MINDSPRING.COM>
Subject: Re: [DCHAS-L] Chemistry Demos for Community
Date: Thu, 30 Aug 2018 16:34:35 -0700
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: D7ADCD1B.38CF6%lhlatimer**At_Symbol_Here**
In-Reply-To <5045A69D3478574D8F28F8600633D87601F5845B9E**At_Symbol_Here**>

Using large graduated cylinders side by side works well and is easier to dump than an aquarium.  Works with cheap and expensive sodas alike.  Cold water enhances the difference.



On 8/29/18, 9:19 AM, "Daniel C Herrick" <herrickd**At_Symbol_Here**MIT.EDU> wrote:

These are all awesome ideas!
I always was partial to the demo where you get a large enough see-through container (a small aquarium works well) and put a bunch of water in it.  Gently place an un-opened can of Coke and an unopened can of Diet Coke on their sides into the water.  The can of regular Coke sinks while the can of Diet Coke floats.  A no-mess low-hazard specific gravity demo.
Note though, before beginning one should carefully consider how to dump the water afterwards since if the container is of some size it can get heavy rather readily.  After all “a pint’s a pound, the world around” so far as water is concerned…

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Daniel C. Herrick, CIH
Senior EHS Coordinator
Mechanical Engineering Department (MechE)
Massachusetts Institute of Technology (MIT)
Email    herrickd**At_Symbol_Here** <mailto:herrickd**At_Symbol_Here**>
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Phone  617-253-2338 (MIT: x3-2338)

From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Kirk Hunter
Sent: Tuesday, August 28, 2018 7:25 PM
Subject: Re: [DCHAS-L] Chemistry Demos for Community
Hi All,
I like low hazard demos – especially ones that leave the audience scratching their heads. Water is my liquid of choice! In addition, I don’t have to worry about anyone trying duplicate the demo at home and getting hurt!
Here are some demos that I “stole” over my 33 years of teaching..  I just modified them for my personality.  Oh, did I mention that they use water.
Now, if you bother to read further, take heed! I hereby entrust you with the SECRETS – something I only entrust to those who understand the “Secrets of the Universe” AND that you will only share these SECRETS with those whom you deem worthy.  (I actually gave some groups a certificate at the end of my presentation with similar wording worthy of coming from Merlin or Gandalf.)
I start my presentation (which is typically to lay audiences or middle/high school students) talking about science and the importance of understanding how matter interacts - and that small molecules, like water, can open doors to understanding complex molecules and reactions.  Nearly everyone knows the formula for water!! But, few have thought past that factoid. So, we begin…
  1. The “Magic” Mason Jar.
Nearly everyone has seen the trick where you place a card on a cup filled (or partially filled) with water. The cup is inverted and the card stays “attached” to the cup. I do this over a large water pail and demonstrate that the water is there by pulling the card away. In most of these demos the cup is opaque plastic. I try to get some discussion on the reason the card stays. Someone usually says something about a vacuum, so I do it again, but with a glass mason jar so that the audience can observe what is happening inside the jar. I replicate the demo with the glass mason canning jar that has a brass ring at the mouth. Place the card on top, invert. The card stays. Then remove the card – the water stays in!!!! Huh????!!!  I tilt the jar a bit to one side and water pours out. I return the jar to vertical, the water flow stops. With a filled quart mason, I can do this three or four times.  


THE SECRET – available only to qualified scientists!! So no sharing with the unwashed – the mason jar has been specially fitted with a piece of screen (for screen doors) that covers the mouth. The brass ring holds the screen in place. Water adhesion and surface tension is strong enough to block the holes. Tilting the jar breaks the surface tension.) At this point my discussion moves to the chemistry of water and intermolecular forces. This can be done in a very general manner for large audiences and young audiences. OR, you can eliminate the discussion all together and have the audience come up possible explanations. I have done this with students. Note: if you are far enough away from the audience, the screen is almost invisible. If closer, just protect the mouth from been seen.)

  1. “The Human Under the Cup” – modification of the card under the cup, but human is the card.
After showing that water can be held back in a cup with a card, I ask for a volunteer. I give them goggles. I ask if they brought a change of clothes. When they respond “No”, I hand them a diaper.. I take a cup, hold it above the water bucket and deliberately pour water into it. I place a card on top of the cup. I tell the volunteer that I am going to place the cup on their head and ask them to hold very still so that they don’t get wet. I confess that I my last attempt at this demo was not successful, thus the reason for the diaper – to clean up the mess in lieu of a towel. I invert the cup on their head and then remove the card. While holding the cup in place, I carefully “inspect” the seal looking for leaks. I make a big deal about this step! The volunteer is directed to stoop and run forward while I hold the cup so as to avoid the falling water.  The audience does the count down. However, I stop it a couple of times to “inspect” the seal. I say something about it leaking and how wet the previous volunteer was – great for multiple shows. I have also held up a wet lab coat. After the volunteer runs from under the cup and everyone has a good laugh, I let the volunteer look into the cup to reveal the secret.  I then pour water into the diaper and rip it open to show a similar substance.


THE SECRET: the cup has a small amount of superabsorbent polymer – sodium polyacrylate. You need to play with the ratio of SAP and water. Too much SAP and it falls out. Too little – a mess!  Almost always, audiences make the connection between the diaper and the demo! I used 16 oz red plastic cups. They seem to work better than Styrofoam. As you are holding it inverted, just don’t squeeze the cup. Yes, it will fall out!  Also, beware of wet tile floors!! This is really the only hazard.  This is also a nice place to reward the volunteer with a t-shirt or some other souvenir.

  1. 3-Cup Water Game
Label three 24 oz white Styrofoam cups, A, B, and C. Pour about 50 ml of water ONLY into cup A.  Ask the audience to keep their eye on Cup A and then proceed to shuffle the cups – a la  "nut under the cup trick.” Keep the letters visible to the audience during this process. When you are through shuffling, ask the audience to identify the cup that has the water in it. Slowly turn over Cup C – no water. Slowly turn over Cup B = no water. Slowly turn over Cup A so that the audience can see inside the cup. Nothing is visible (if you keep moving).  Smile. Move on. Nothing to see here.


THE SECRET: Cup A has a small amount of SAP. In the white Styrofoam cup, the SAP-water mixture is almost invisible, especially in a tall cup. This is a one time demo, but if done after the “Human Under the Cup”, many will figure it out. Let the lighting work in your favor to limit the visibility into the cup as you turn it over.

  1. Sinking Ice (Also a great bar bet!!!)
Two 1-liter graduated cylinders are filled with about 750 ml of liquid. Place a small ice cube into one – it floats. An ice cube placed in the other cylinder sinks.


THE SECRET: one cylinder is filled with water, the other with alcohol. The density of ice is ~0..98 g/ml. The density of alcohol is ~0.78 g/ml. I used isopropanol. Obviously, the ice sinks in the alcohol. This leads to a discussion of specific gravity. After seeing this, I gave students in a lab the problem of finding the density of some small polymer samples. They used this demo as a basis and devised a simple density-gradient column!!


The bar bet? Use your favorite bourbon, etc. Just make sure the glass has enough bourbon in it and the ice cube is small enough so that it can be observed sinking. The density of neat bourbon is ~0.85 g/ml. Be sure to retrieve the ice cube BEFORE it ruins your drink!!


These are fun illusions and they can lead into some interesting discussions about the nature of matter, intermolecular interactions and how understanding small molecules helps us to understand larger ones – polymers and biomolecules.  I call them “Demos with a Purpose.”
I have done these demos for both large and small groups and even at family gatherings. I have been told that the “cool factor” is there and I fun with the volunteers and audience. I have done back-to-back shows, but it does require a little set up – and maybe a mop and a towel. Premeasuring everything for each “set” makes transition time shorter.  I would emphasize practicing before doing to get the proportions correct and the timing down.
So, enjoy and have fun!!
Kirk Hunter
For those wanting to steal my demos:

Demo 1: Magic Mason Jar

5 gal bucket with about 3 gal water

2 – 16 oz red plastic dixie cups

1 qt mason canning jar with ring (Size should be large enough for the audience to see the water inside,        but also comfortable for your hand to hold. One quart jars worked for me.)

Metal wire mesh screen (used for window/door screens) I used anodize aluminum screening from a        home improvement/hardware store. It is dark brown/black and is nearly imperceptible from a distance. Use lighting to your advantage to help hide it! It is fairly easy to cut. Just don’t use     your spouse’s good fabric scissors!!

4x6 note cards  (cards should have some clay content – otherwise, they will absorb water)

              Demo 2: Human Under Cup
              5 gal bucket with about 3 gal water
              2-16 oz red dixie up (one for filling a prepared cup)
              Sodium polyacrylate (SAP) – amount varies
              4x6 note cards
              Diaper (or other commercial product with absorbent)
              Goggles, towels
              Demo 3: 3-Cup Water Game
              3 – 24 oz white Styrofoam cups
              Sodium polyacrylate (SAP) – amount varies
              Demo 4: Sinking Ice
              2 – 1 liter glass or clear cylinders
              Ice (small enough to fit into the cylinders)
              Food coloring – may help with contrast and seeing the ice cube
Sent from Mail <>  for Windows 10

From: Wilhelm, Monique <mailto:mwilhelm**At_Symbol_Here**UMFLINT.EDU>
Sent: Tuesday, August 28, 2018 3:06 PM
Subject: Re: [DCHAS-L] Chemistry Demos for Community
I personally don’t like using the hexanes outside.

Monique Wilhelm
Laboratory Manager
Department of Chemistry & Biochemistry
University of Michigan – Flint

From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Reinhardt, Peter
Sent: Tuesday, August 28, 2018 3:41 PM
Subject: Re: [DCHAS-L] Chemistry Demos for Community

I think the nylon rope trick is amazing.. Isn’t that relatively low hazard? – Pete Reinhardt, Yale

From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU] On Behalf Of Eggum, Janet
Sent: Tuesday, August 28, 2018 3:19 PM
Subject: [DCHAS-L] Chemistry Demos for Community

Hello All,
Our Chemistry Dept.  has a community night, were they do demos.    Typically, this has taken place in a lecture hall with a demonstration fume hood.    Recently, our new science building came online, and the coordinator of this community night would like to do the demonstrations in a public atrium area.    I’m looking to the collective group for help.   Do you have a demonstration that is low hazard, but HIGH cool factor that could be an option?   
If you would like to contact me offline, my email is jghamo2**At_Symbol_Here**
Thank you so much for your help.
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