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Posts Tagged ‘gak’

Chlorophyll analysis

Dr. Rakesh Mogul and students conducting chlorophyll analysis of soil crust samples using IR absorption

On our fourth day at the CSU Desert Studies Center on Zzyzx Road, we continued our analyses of the biological soil crusts and began to put together the results of our studies. The CSU students extracted chlorophyll from the crusts and the soils underneath, then measured amounts by looking at infrared absorption lines at several wavelengths that are characteristic for chlorophyll.

GPS data for soil samples

Mapping the GPS coordinates for our samples

 

I helped Mary Beth start mapping out the trends we saw in the various chemical analyses of the soils at the three main sites. She did most of the work, looking up geological maps of the area around Baker and the various types of rock outcroppings and unconsolidated valley fill deposits, then located all our sample sites from the GPS coordinates we’d recorded on Monday and created gradient arrows across the maps showing how the various elements and compounds trended between locations.

geologic map of area

Charting soil chemistry changes onto a geological map along Kelbaker Road

Most of the trends were to be expected, but a few were surprising. For example, there was more aluminum and calcium in the soil at the low density site than at the other two. We joked that all the pop cans left as trash scattered around the low density site (which was near Baker) might have been the source, but of course that would be impossible – it would take a huge number of cans, completely oxidized away, to leave any kind of aluminum residue. So we looked at the maps for possible sources. This site was in more of a playa lake bottom and probably has more clay in the soil (which we can confirm with the soil mechanics group), and clay is an aluminum silicate. The calcium could come from nearby limestone deposits.

Desert Studies Center

CSU Desert Studies Center on Zzyzx Road in the Mojave National Preserve. Baker, CA is in the distance.

Overall, our project is a good example of how field research is carried out –you start with a question and a site to test it at, consider the possible ways to isolate the data you need from all the other variables in the environment (such as pop cans), come up with experimental procedures and protocols, then travel to the site, collect the data, conducting both field and laboratory analyses, then analyze the results and try to make sense of it all. It isn’t quite the formal scientific method we teach in middle school science classes. Often the statistics aren’t as strong as you would like because you’re using ANOVA (analysis of variance) or MANOVA (multiple analysis of variance) techniques. Since many different conditions are being tested, and you have to see how they all stack up and compare, often there are only a few data points per data set.

Soda Lake playa

Soda Lake playa in the Mojave Desert

It’s not as neat and predictable and controllable as a lab experiment, but it’s a lot more fun. For us, our biggest problem was trying to draw conclusions from the tests we ran, which were more qualitative and less reliable than we would like. The one test kit was designed for gardeners to use, and had test strips that only showed low, medium, and high results without any kind of ratio data. We also had some more individual tests for specific elements and compounds (such as chlorides or sulfates) that were a bit more numeric (at least they had scales) but not much more reliable. Often when we tried to do a sample a second time, the results weren’t very consistent. So we’d have to run the test a third time, or try to filter the soil better, etc. For our final results, we can’t rely on these inaccurate field tests. We’ll have to send the samples in for detailed lab analysis to find out the precise percentages of different elements. It will be interesting to see if our field results match up.

Borax stripes

Stripes in salt falt where borax and soda have been scraped up.

I also took the opportunity to climb a low hill behind the lab with my camera equipment to get a good look at the surrounding desert. From up there, I could see back to Baker and I-15 in one direction and toward the Kelso Dunes and deeper into the Mojave National Preserve in the other direction. This research station was originally a way station on the overland stage route, then eventually became a center for borax mining. On the other side of the hill, parallel trenches can still be seen where the borax powder was scraped up and piled, to be shipped out by the famous 20-mule teams. This is the low point in this valley and a salt flat/playa lake surrounds the Soda Springs area. It probably looks pretty barren and inhospitable to most people, but this is the kind of scenery I’m used to growing up in the Pahvant Valley of western Utah, with Sevier Lake and frequent evaporated alkali deposits to the west of my father’s farm. The weather has gradually warmed up from the freezing wind that greeted me on Sunday night.

borax minerals

Borax minerals and a model of the 20-mule teams that hauled the borax.

The commons room has some displays showing borax crystals and brief descriptions of how the mining was done, as well as the natural history of the station with local flora and fauna. The boron compounds (usually borates such as sodium and calcium borate) are generally known as borax, and have many uses. Borosilicate glass is highly heat resistant and is used in chemical lab ware, where we know it as Pyrex. It is also being used to contain and store radioactive wastes; since glass is highly stable chemically, the spent nuclear fuel rods are mixed with the glass in the form of marble-sized spheres or as sheathed glass columns. Borax also helps to extend laundry detergent, and provides the green color for fireworks.

History of borax mining part 1

The history of borax mining, part 1

I use borax to create the cross-linked polymerization when I make “gak” in my chemistry classroom. Here’s the recipe: take two paper cups. In one, fill it about ¼ full of warm water and ¼ full of white glue, plus a little food coloring. In the second cup, fill it about 1/3 full of warm water and about 10-15 grams of borax powder. Stir it up well, then mix the two cups together and keep on stirring. At first it will be a sticky mess, but in a minute or so the cross-linking between the glue strands will begin and water molecules get trapped in the borate links, making the whole thing into a fun, gloopy concoction that can be kneaded and molded.

I am including here two photos of the poster that describes borax mining, which you can read to find out more of the history. I’ll create a dedicated post later on going into more detail after I do some more research.

Timeline for Soda Springs Station

Timeline for Soda Springs and Zzyzx station

History of borax mining part 2
History of borax mining, Part 2
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Gay eyeballs

Making gak eyeballs at Walden School

This last week was our final week of Fall Semester at Walden School, and for their final test my chemistry students planned, practiced, and presented chemistry demonstrations to their peers and to Walden’s elementary classes. Altogether five groups of students presented to the elementary school on Wednesday, Dec. 15 and the rest of the student teams presented on Friday, Dec. 17.

I’ve discussed my rationale for doing this in previous posts: that this is an excellent method for generating excitement about STEM in elementary students as they see their older siblings and high school students working with and presenting science. Certainly the younger students were very excited and attentive; they were eager to participate and asked good questions.

Raising hands

Students at Walden School participating in chemistry demonstrations

For me, though, the real reason for doing anything in my classes is always how it will benefit my students. Taking 3-4 days out of our curriculum to practice and present these demonstrations is hard to justify unless it has strong pedagogical advantages. The justification is this: as my students write up their demonstration scripts and outlines, as they practice talking about the science they are presenting, and as they prepare to answer questions from the audience they are thoroughly learning the chemistry behind their demonstrations. They are going beyond hands-on labs to share what they have learned, and that learning will be indelible.

Karlie and Sofia

Karlie and Sofia demonstrate hand warmers

The topics of the demonstrations had to related to the individual element/materials research project of one of the group members, which they are continuing to work on. Here’s what was presented:

Sofia, Karlie, and Jerry demonstrated the principles behind hand warmers by showing the rapid crystallization of sodium thiosulfate crystals that had been heated and then cooled down. They also talked about crystals in general.

Making gak

Mari and Casey help students make gak

Ryan and Casey, with help from Chelise, Lindsey, and Mari, demonstrated how to make gak (a polymer made out of white glue and borax powder). This is an old standby demonstration, and the kids really enjoyed it.

Copper demonstration group

Genny, Rachel, Jared, and Morgan demonstrate copper's properties

Genny, Rachel, Morgan, and Jared demonstrated aspects of copper chemistry. They handed around samples of copper ore (Rachel’s uncle is an engineer at Rio Tinto’s Bingham Canyon Mine in Utah) and showed a methanol version of a flame test (including copper salts). Jared demonstrated the alchemist’s dream reaction: turning copper into gold (actually brass).

Kinesthetic activity

Sid and Sam use a kinesthetic activity to demonstrate magnetic induction

Sam and Sid, with help from Josh, presented the idea of magnetic induction and discussed how modern electrical generators work. Sam actually built her own alternator and induction coil, and Sid presented on his research about the use of wind power to generate electricity. They also created a fun kinesthetic activity to show induction.

Burning magnesium

Karl and Nicona demonstrate burning magnesium

Karl, Nicona, and Tanner presented on the properties of the elements; they did a flame test as well, and demonstrated what magnesium ribbon looks like when burned and how fireworks get their colors. They also had sparklers for each of the students to try out.

Cabbage pH

Sonora, Dallas, and Morgan demonstrate cabbage pH

In class on Friday, the other groups presented their demonstrations. Sonora, Morgan, and Dallas presented the red cabbage pH demonstration that is one of my favorites.

Untarnishing silver

Mari and Holly demonstrate how to un-tarnish silverware

Courtney, Holly, and Mari showed how to untarnish silver using baking soda and aluminum foil. They even included a correctly balanced chemical equation, although we won’t be learning about those until we return in January.

Dry ice group

Libby, Lindsey, and Chelise demonstrate the properties of carbon dioxide

Chelise, Lindsey, and Libby presented the properties of carbon dioxide gas and dry ice. They showed how regular matches go out in carbon dioxide, but that magnesium burns even brighter when placed in carbon dioxide.

Olivia and Jace

Jace and Olivia explain the ingredients of gunpowder

Jace and Olivia talked about gunpowder, how it is made, and why it is dangerous. Jace has experience working with black powder (he has his own muzzle loader – this is Utah, after all) and he created some raw gunpowder, which he burn outside. They also demonstrated the “fire writing” demonstration of drawing on a piece of paper with a saturated solution of potassium nitrate, then touching a wooden splint to the edges of the writing to see it burn letters through the paper.

Josh and Jess

Josh and Jess demonstrate the principle of density with salt solutions

Josh and Jess presented on salt solutions and how they can be used to determine the density of objects. They showed how an egg will sink in pure water but will float in salt water.

We also videotaped as much of the presentations as we could and took quite a few photos; those students that weren’t helping present helped with the photography.

Burning gunpowder

Burning gunpowder

When their demonstrations were done on Wednesday and Friday, my students were excited about what they had done and the feedback they’d gotten from the younger students. They still have to learn some showmanship and presentation skills (which we’ll continue to work on), but based on what I saw and what the elementary teachers reported, the science content was excellent. They and their peers filled out evaluation forms (and I will as well) so that they can improve on their presentations for the next round in January.

Golden pennies

Golden pennies

It was a lot of work to prepare for this. Now my lab room is a mess and I’ll need to take a day during Christmas break to clean up and re-organize (and I think I forgot to throw out the leftover red cabbage pulp that’s in my trash can, so I’d better go clean up tomorrow). But despite the work and the lost time, I’d say these demonstrations were well worth it. As we go through the second semester, the students will present at least twice more, including a final time at a back-to-school night for their parents. We’ll polish the delivery, add more science explanations, create slide shows and videos to supplement their demonstrations, and by the end of the year these will be incredibly well done.

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