The Real World

Yesterday was my first time going into the real world with my kits. I'm working with an afterschool program in a nearby town. I get there a little after my school day ends, set up, run some activities, clean up, and head home.

Chromatography

You'll need:

• absorbent paper (paper towels will work)
• a solvent (water, rubbing alcohol, or vinegar)
• pens/markers - these depend on what solvent you're using. For example, Sharpies are alcohol based, so this won't work if you are using water. Common water soluble brands are Pilot, Foray, and Uni, but there are many more. Washable markers tend to be water soluble.

Draw a line about an inch from the bottom of your absorbent paper. Draw a small dash for each color of pen you are testing, leaving some space between each dash an between the edges. Cover the bottom of a container with a small layer of the solvent. Hold the paper in the water (or alcohol), being careful not to let the dashes be submerged. You can clip it to the edges, tape it to a pencil lain across the top, or simply hold the paper.

As the solvent travels up the paper, it will bring the ink with it. If the ink is made of multiple components, these will separate.

Chromatography is used to help separate something into components. For example, if you have a sample of ink from a message, you can use chromatography to compare it to other inks to figure out which type of pen wrote the message.There are many types (gas, liquid, thin layer, and paper) but this technique is paper chromatography.

The paper is called the stationary phase, and the solvent is called the mobile phase.  The substances affinity to each phase is what determines how far up the page the compound moves. Since "how far up the page is relative" - you could let the ink sit a long time in the solvent so the ink has more opportunity to be in the mobile phase - a better way to compare is needed. This is called the R_f value. The formula is R_f = [distance traveled by compound]/[distance traveled by solvent]. Comparing R_f values allows you to compare different substances.  If two substances have different R_f values then they are obviously different. However, just because the R_f values are the same doesn't mean the substances are.

One compound will have different values in different solvents. To verify two inks are the same, do chromatography with more than one solvent.

At The Fair

Last weekend my town held a fair and I got to run a booth. I thought I would share my experiences with it. While it was overall successful (and very fun) there were several mishaps along the way.

Glurch

Glurch is very similar in behavior to silly putty (meaning it is also a non-Newtonian fluid). You combine Elmer's school glue and water in 50-50 ratio. Try and make the mixture completely homogeneous - in other words, no areas of extra water or glue, blend them completely. Then make a saturated solution of water and Borax. Borax is a laundry booster which helps lift stains. You will probably need a teaspoon for every cup of water. Add a small amount of this solution to the glue/water mixture and stir until it gloms together. It looks pretty slimy at first, but as you play with it more the extra water is removed and the Glurch becomes more putty-like.

Oobleck

This one's a classic.  Combine cornstarch and water in approximately equal proportions. And if you want, a little food coloring. When you start playing with it you'll notice that it's a little .... weird. You can actually grab a handful and pick it up - but as soon as you stop applying pressure to it the oobleck starts to drip out of your hand like a liquid. And if you get a speaker, cover it with plastic wrap and pour on some oobleck, interesting things start to happen.