tech rehearsal

Patti Galvan of ACS called on Friday and we talked for close to two hours. We firmed up which demonstrations would be done for the NCW event, which was a very good thing. Hey, it's only two weeks away!
She is sending the materials for the demonstrations, but has already emailed the procedures to me.
That means I could have a bit of a run-through, get my hands wet, so to speak.
Literally as well as figuratively.
That's exactly what I did yesterday.
(smile)

"Yellow And Blue" called for the use of ordinary
household products to demonstrate the interactions between liquids.
What "ordinary" products?
Water, isopropyl alcohol, saltwater.
The water has two drops of blue dye.
The 70% rubbing alcohol has two drops of yellow dye.
The "lab bench" is a plastic plate.

A toothpick was used to move the blue liquid to the
very edge of the yellow liquid, taking care to not actually mix the two.
The point of using the toothpick (get the joke?) was to allow mixing of the two due solely to the natural movement of the molecules within each liquid.
In other words, how miscible were the two?
What affinity was present?

So, here was the final result.
(I've included a blue spot of the original water for color comparison.)
As one would expect, combining yellow and blue made green, with the two liquids mixing together quite well.
(Hence, the other 30% in the bottle of 70% isopropyl alcohol is water.)

The next part of the experiment called for water (in blue) to take on a 15% saltwater solution (in yellow).
The two liquids were again separated by an empty space.
Then, a toothpick was again used to pull the water until it was just touching the edge of the yellow solution.

That led to a very different response than was seen
in the first experiment!
Sure, where the two liquids are together there is a
green color... but notice the yellow.
That saltwater does not appear to be combining with
the plain water.
Instead, the water seems to have slid on top of the solution with the salt.

That is exactly what happened, too.
The hydrated sodium chloride in the solution caused a bonding that prevented the two liquids from combining.
Instead of merging, they remained separate.
The kids will then get a third "mystery" yellow solution which they will have to identify, based on its interaction with water.
Chemical analysis to puzzle solve!
(smile)

Then I decided to run a variation of the "Rust Is The Crust That Makes Things Bust" experiment that's given in the NCW edition of "Celebrating Chemistry".
I wanted to include that demonstration for my event on October 20th, but it requires an overnight wait.
So, I ran the lab at home to get the results for them!
The steel wool in the leftmost cup had been saturated with olive oil.
The same was true for the second cup's contents,

but with partial submersion in water.
The third cup had plain steel wool that was partially submerged in water.
The fourth cup again had plain steel wool, but this time it was completely submerged in water, then a half-inch layer of olive oil finished it off.

Here is a side view of the four cups, all left in the same environmental conditions.
Specifically, they were placed in my sunroom and left uncovered for twenty-four hours.

Today, I avoided even peeking at the cups and their contents until an hour ago.
Not that it mattered whether I looked at them or not -
I could smell the iron oxide from my kitchen doorway.
What an unpleasant, pungent odor!
The liquid in two of the cups was also quite orange.
But the other two cups were looking pretty good.

This photograph compares the first and second cup, the two which had the steel wool coated in olive oil.
In the first cup, no liquid was added, but the steel wool was exposed to the air, so oxygen was able to interact.
Some slight rust is present, but it's not throughout.
However, in the second cup, the oil-coated steel wool was exposed to both water and to the air and a considerable amount of rust is visible.

Now, consider the samples in these two cups.
The steel wool was left bare in both instances and was placed in water in both experiments.
In the third cup, where the steel wool was exposed to both the water and the air, the look and smell of the liquid is the most repulsive. Rust is pervasive throughout the material.
However, in the last cup, the steel wool looks almost pristine. Although it was subjected to water, no oxygen aid in the conversion to iron (III) oxide, i.e., rust.

All in all, a most successful experiment that I wish could be performed at my National Chemistry Week event in two weeks.
Since that won't be possible due to time constraints, I've done the next best thing.
I've packaged the cup contents, sans liquid, and included the paper towel used to wipe or dry the steel wool.
Pretty nifty, isn't it?
Now, those baggies are in my freezer and the cups and their contents are away.
Ah, back to clean air!
Fun, but definitely very odoriferous!
I'll be waiting to do more experiments when the boxes arrives from ACS.
Maybe I'll be able to arrange a run-through with the volunteers?
Oh, that would be wonderful... plus, I'd have the chance to meet them.
(smile)