Showing posts with label chemistry. Show all posts
Showing posts with label chemistry. Show all posts

Wednesday, May 8, 2024

Chocolate Tempering Activity

Tempering chocolate is one of those things that seems hard until you learn about it, and then it seems easy, and then it seems hard again the more you learn about it. (Sourdough bread is the same way.) Keeping your chocolate in temper is fairly simple on the face of it, and yet when you're dipping chocolates, sometimes it is delicate and gets out of temper for no discernible reason, even though it seems like you should easily be able to get it perfect every time. 

Anyway, we learned all about tempering chocolate, why it works the way it does and the underlying chemical processes. And then we tempered (and un-tempered) a bunch of chocolate and dipped things in it. Yum! Even though it all tastes good, you really do miss that textural snap when the chocolate is properly in temper (Phase V crystal formation).

And here is the link to our previous unit's chocolate tempering day!
Ooh, look how shiny these pretzels are. Perfect. 
A lovely assortment of dipped items
Out of temper, in temper
Out of temper (fat bloom)
A beautiful white chocolate dipped strawberry
Junie's bunny strawberry!
Gus's strawberry

Sunday, October 25, 2015

The Spiral Jetty and the Pink Salt Lake

We didn't do this field trip as part of a specific unit, but it was such an interesting and educational outing that I thought I'd post it here as well as on my other blog. I think this would be a great field trip for a rock and mineral unit…or as part of learning about environmental and installation art…or when studying archaea and other microbes…or any number of other things. It was SUCH a cool place, I am sure we will find any number of excuses to go back! :)

*****

Last year, my friend Andrea and I decided we must go see the Spiral Jetty (the environmental sculpture/earthwork by Robert Smithson) up at the North end of the Great Salt Lake. (The children and I had been cursing ourselves for not going to see it the last time we were in the area, as there is really no other reason to ever be out that direction!) But we kept having to put it off…first she had a baby, and then I had a baby—but finally this October we managed to get all eighteen (!!) of us together, husbands and kids included, to make it happen! (In spite of Andrea being pregnant again…ha!)

We drove waaaaay out, past the Golden Spike National Historic Site, onto the (fairly well-maintained) dirt road to the site of the jetty. When we got there, it was raining quite a bit, so Sam and I shooed the kids out of the car to explore while I fed Theodore and we stayed warm and dry. Luckily we had brought rain boots for everyone, since Andrea had told us it would be wet and sandy/muddy down by the jetty. (And here's a great post with advice if you want to make this trip too.)

After a while the rain fizzled out and we emerged from the car. The children were having fun wandering hither and yon. It's such interesting countryside out there. Stark. Very stark. 
Spot the two boys!
You can climb up the rocky hill above and see the whole spiral of the jetty as you look down, but what you instantly WANT to do is climb down the hill and walk along the jetty itself, spiraling inward till you reach the center. This was the time when I was congratulating myself for having worn rain boots (or "gum boots" as Andrea calls them, or "galoshes" as Sam calls them—very diverse bunch, the lot of us), as there was lots of standing water and a great quantity of strange, wet, salty sand.
Everyone immediately started drawing things in the sand, of course. There was a very dark, almost black, layer you could see beneath the sand, if you dug down a bit. Daisy drew a tiny Spiral Jetty within the big Spiral Jetty. Thought-provoking!
Goldie looked like a hauntingly beautiful elf-maiden. Wearing rain boots.
Every so often you'd come across a larger concentration of salt (I suppose it was all through, mixed with the sand, but some areas seemed to be just salt) and you could see where the distinctive cubic crystals had formed. Sebby kept bringing me masses of them to look at. They were beautiful.
After a fair amount of scraping sticks along the sand and gathering salt crystals and so forth, some of us felt beckoned by the call of the sea. By which I mean, you could see a pale stripe of water glinting quite far off, and we wanted to investigate. I conscripted Abe into service carrying Theoda and off we went, across the stark white expanse.
It seemed to get saltier and saltier as we went, until we didn't in fact seem to be walking on sand at all, but salt-encrusted sand…and then, just salt. There were all kinds of interesting formations, like these salt-balls, which look quite delicate and furry, but didn't even crumble when you stepped on them. You could grind them slightly under your foot or between your fingers, but only with some effort.
The clouds were starting to peel away from the sun in frayed greyish strips, like last bits of paper towel clinging to the glue on the roll. This meant the sunlight could leak out around the edges and shine on patches of the salt in front of us every now and then. It was very beautiful.
And we started noticing the great white desert we had set off across wasn't actually so white as it had first seemed.
We've been to the Salt Flats a few times, and to some salt-flat-like areas, and there were some similarities, but this seemed different. For one thing, it was starting to become quite…pink!
Very pink, in fact. And there were lots of little rivulets and channels and crystallizations going on that you couldn't see from far away.
And lots of desiccated beetles and crickets and other insects, lying there amidst the delicate salt crystals and looking almost…mummified! It gave the place a slightly sinister feeling. Imagine if WE had had to cross this wasteland without any fresh water! 
It got pinker and pinker, and as we got close to the water, the sun came right out and gave the water an almost pinkish glow. I kept wondering what trick of the light was causing it.
And then we got right up to the water and I realized: it didn't look pink. It WAS pink! I was so surprised! Astounded, in fact! I kept saying that I felt like we were on another planet, and it seems like hyperbole, but it really did feel disorienting and otherworldly, because nothing in this world could prepare me for a pink ocean (which is what the lake seems like from the shore, vast as it is). I kept checking the sky to see if there were also two moons rising or something of that sort.

As I mentioned, I've been to the Great Salt Lake a lot—Antelope Island, the Salt Flats, Willard Bay. And nothing ever seemed remotely pink about it! But upon looking it up (after we got home), I learned that the Great Salt Lake is divided into two sections by a railroad causeway. It used to be made of wood and allow water to flow under it, but when they built a stronger one out of rock and earth, it basically cut the lake in half. And—this is the important part—ALL of the tributaries to the Salt Lake flow into the southern half of the lake. So, while the south part of the lake is quite salty, at 13% salinity or so, it is being constantly refreshed by the Jordan and Bear and Weber rivers. But the north arm of the lake stays at more like 28% salinity! It's so salty that the salt actually precipitates out of the water and onto other nearby surfaces.
There aren't too many things that can live in the Great Salt Lake anyway, but in the north arm, not even the brine shrimp and most algae can survive. The only things that can live there are microbes called halophiles, and those have a pink pigment in them that gives the lake and the salt its color. You can see the distinct color differences between the north and south sections of the lake in this photograph, and this time-lapse video. It is amazing. And lucky for us, we happened to visit in the Fall, when I think the water is at its pinkest (the pink-tinted archaea having had their heyday during the warm summer, presumably).
The other thing we noticed immediately, getting close to the water, was a long ruffle of white, soapy foam clinging to the edges of the lake. I read that this is also a by-product of the microbes: they have lipids in their bodies that actually make this sort of soapy material. It was quite lovely. It was very light and made your hands feel sort of smooth and dry after touching it. 
There was a bit of a wind, and as we looked down the shoreline, we started seeing all these little balls come rolling toward us at top speed, like slippery little tumbleweeds.
It was the foam! Little balls of foam being blown off from the main mass and then going skimming along over the salt. I couldn't even get a clear picture of one, they were blowing by so fast. We were so delighted. They were like little furry animals rolling by.
The advance party having scouted out the territory, the rest of our group began to make their way over to the water. The sun was shining full and gold on that one lonely little hill, by this point.
There was even a very faint rainbow!
When Daisy saw the water she was very, very pleased. "Pink! For ME!"
Junie was happy about the big pink salt-slab she broke off.
Everyone immediately began to play with the foam.
Oskar was especially taken with the stuff.
Harriet looked like a sea-maiden emerging from the foam.
Some felt they must enter the water to truly commune with it.
The light kept changing as the sun got lower and went in and out of those threadbare pieces of cloud. Sometimes the water looked pearly-pink against the purple-blue sky. Sometimes, as the light came through the waves or scattered across the top of the lake, it looked almost like rose gold.
The urge to run through those piles of bubbles really was quite irresistible.
Finally we managed to pull all the children away from their bubbly pink playground and herd them back toward the jetty—salty, wet, dirty, and complaining that various spots on their legs and feet were stinging—which they were, of course, from the salt. Junie had large red raw spots on her calves where the salt water had gotten into her boots and rubbed the skin off. But everyone was mostly excited and happy, all the same. It was impossible not to be drawn into the drama of our surroundings.
We played around on the Spiral Jetty a bit more, watching the sun set and the light sweep across the clouds.
See the tiny crescent moon!
It had warmed up while the sun was out, but now it was getting colder, and everyone devoured Andrea's white chili and the potstickers and cornbread we had brought. We were like a pack of ravenous wolves. Or perhaps a plague of locusts. Everything tasted like the nectar of the gods, as things do when you eat outdoors at dusk, having first exhausted yourself in the salty air.
That stark, rocky hillside glowed for a moment under the clouds.
A vapor trail gleamed.
And the sun, obligingly, made one last spectacular appearance over the Spiral Jetty. 
It was a very-nearly-perfect day. And we saw bunnies hopping in the desert darkness all the way back along the dirt road!
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