Thirteen (mostly) Chemistry Demonstrations in 280 Characters Or Less

  1. Ground #helium balloons with a bunch of grapes. Then remove 1 grape at a time until the buoyant & gravitational forces balance out. The balloons will be suspended in the air. Children quickly catch on and have injected a little #science into an otherwise dull wedding reception.
  2. Add copper to HCl & watch nothing happen. Add Cu to HNO3, & NO2 or NO forms, depending on the acid’s concentration. Add CuO to citric acid, wait a few days & a (patina-like?) material forms.
  3. ZNO44To a beaker, add sand and a 50% solution of methanol. Then add spatula tips of zinc oxide powder. Close lights. Transitions are very temperature-dependent and different parts of the flame create a variety of colors. Students prefer demo to drugs.
  4. Add calcium to water & phenolphthalein. Collect H2. Ignite it. Color change in solution reveals hydroxide formation. White precipitate of CaO settles below fuchsia solution. Filter it. Blow into solution of Ca(OH)2 to form CaCO3. More CO2 forms acid, gets rids of cloudiness.
  5. ammoniaAdd 2 drops of bromothymol blue to a (pH ~ 4) solution in a flat-bottomed flask. Add dilute NaOH to beaker. Bring the flask to a boil for 3-5 minutes. Remove heat source & wrap a cold, wet rag around the flask. Be awed by work of ΔPV.
  6. Get a hand-held digital microscope. Use it to reveal  the sensuous surface of a grapefruit, an aborted seed; and the oxidation of copper in an old penny. 

SANYO DIGITAL CAMERAChip off 5 samples from a boulder. Use water displacement in large cylinder to find the volume of each piece. Mass each rock. Obtain average density. With latter & an estimate of the boulder’s volume, get an estimate of the boulder’s mass.
8. Get a thin flow from a water tap. Wrap cotton shirt around a plastic comb. Rub it. Move the comb towards the water without touching it. Watch the stream bend like a banana. Water is neutral, but something charged within it is attracted to the oppositely charged comb.Static 9. Demonstrate that old pieces of magnesium often won’t flash in a Bunsen burner flame. Their surface has reacted with air. Wipe a piece with a paper towel that’s wet with dilute acid. Dry, weigh, ignite& look away! After it flashes, reveal that white residue’s mass > than original.
10. CO2Add two drops of bromothymol blue to 4 different test tubes containing tap water. Add distilled water to the 1st; it remains green. Add baking soda to 2nd, get blue. To the 3rd and 4th add vinegar & dry ice (CO2). Both go yellow as both additives lead to H+.

11. Ignite a hydrogen-filled balloon. Note red color from excess H2 incandescing in heat of reaction. Fill a 2nd balloon with 2:1 ratio of H2 to O2 & ignite; observe no red color. Fill 3rd balloon with hydrogen and add a little copper sulfate. Explosion becomes green-colored.

12. Spread a few grams of iron filings on a filter paper. Place it a magnetic stirrer. Turn it on at medium speed. A beautiful display of a magnetic field in motion ensues. It resembles a living colony of microorganisms.

13. The calcium carbonate in blackboard chalk is long-baked, so it quickly settles, and more stays out of the respiratory system. Yet, if you examine any ledge or border high above the board, it fills with chalk dust over the school year. How? Brownian motion.

14. Imagine someone you has wronged you. Imagine taking a wet sheet of newspaper& sticking it on the guy’s windshield on a cold day. Due to H-bonding he’ll never be able to scrape it off, unless he has access to hot water. Imagine writing on the paper, “Revenge is best served cold.”

More to come.

2

How to Maintain a Lawn Without Herbicides or Synthetic Fertilizer, Version 2

Although I can appreciate the benefits of grass around the home, I am not a big fan of big lawns. They demand lots of energy and water, and in return, our family, which consists entirely of humans, cannot eat grass. For this reason, we have devoted most of our backyard to a vegetable garden, shrubs, berries and fruit trees. Unfortunately, a borough by-law prevents us from growing tomatoes or other produce in front of our home, so I maintain a small lawn.

Here’s what it looks like today, in early September.

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Although not “impeccable” by conventional standards, it’s quite green, and yet it has not ever received any herbicide or pesticide in its entire 21-year existence. For the last 15 years or so, it has not received any synthetic fertilizer either. So how do I keep it green?

I add used coffee grounds to my lawn throughout the summer. In the spring I also spread a few composted chicken manure pellets with my backyard’s compost in areas that have mostly grass. It also gets some urea(a nitrogen-source) from dogs who pee on my front yard during the winter. What’s wrong with synthetic fertilizer? Aside from being expensive, it inevitably spreads beyond the lawns’ borders, eats away at sidewalks, and runs off into our storm drains and river.

Next we come to the subject of “weeds”. Using such a term demonstrates ignorance of botany, which is a beautiful but underappreciated science. By not using herbicide, I save money, don’t risk health effects and allow plants like bird’s foot trefoil (Lotus corniculatus) to survive. Before flowering it looks like this patch from my lawn:

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It is a legume so it provides some of its own fertilizer thanks to a bacteria in its roots. If I don’t mow the lawn for a while, the trefoil produces attractive flowers that look these:

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Other non-grass plants worth tolerating are herbs like oregano, which spread to the lawn from the rock garden. If you look carefully, there is also parsley at the bottom center of the picture.  P1170382.JPG

There are three plants that I treat as “weeds” because they would otherwise grow at the expense of the grass, oregano and trefoil. They are dandelions, plantain and crab grass. To remove dandelions and their entire root, I use a tool. But trefoil does compete with them nicely. The other two have shallow root systems and are easy to pluck out with my thumb and index:P1170378.JPG

These were removed a little late. They have flowered and could have already spread their seeds. It’s best to learn to recognize them and pull them out earlier and donate them to the compost pile.

To encourage a deeper root network, I rely on rain, and even during dry spells, I water grass only every second day.  To conserve more water I use some water from a rain bucket positioned below the roof gutter. Since the patch of grass is only about 300 square feet, it takes me less than 15 minutes to hose it down.

Hopefully, if you haven’t already adopted similar practices, you will now be willing to save money, learn some botany and spend a little more time outdoors.

2

Side-Benefits of Birches’ and Beans’ Friendships

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Frankia bacteria with vesicles

Although it’s common knowledge that there is a beneficial relationship between members of the legume family and Rhizobium bacteria, less people are aware that there is a similar relationship between the members of the birch and alder family and a bacteria called Frankia. What’s noteworthy is that in both mutualisms, legumes and birches gain more than just ammonium, which the bacteria form by converting nitrogen from the air with their special enzyme nitrogenase. (For those of you who are also salivating to find out what plants do with ammonium, they use it to give glutamate an extra amino group as it becomes glutamine. The latter yields an amino to α-ketoglutarate which regenerates glutamate as it transfers it to variable intermediates. Those finally become a variety of essential amino acids. )

Before revealing the other benefits, let’s look at the Frankia nodules that form around the roots of Alnus glutinosa, the common alder tree. They are the orange clumps you see throughout the picture below.

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A mutualism between alder roots and Frankia nodules

When alder or birch trees are still young, it’s been shown that the Frankia infection lowers their ability to produce tannins and other compounds, making them more appetizing to herbivores. But the drawback is short-lived. The synthesis of deterrents accelerates as the treelings quickly mature, thanks to the extra nitrogen from Frankia, and this allows the trees to survive.

Mexican-Bean-Beetle
a Mexican Bean beetle

Lima beans, which form nodules with Rhizobium, use the nitrogen-bonanza to make their leaves richer in cyanogenic glycosides that are poisonous to Mexican Bean beetles. The more nodules they have, the more protective compounds they produce. Researchers confirmed that hypothesis by chemically degrading the poisons with enzymes in closed Thunberg vessels and then using spectrophotometry to measure the amount of hydrogen cyanide  HCN released.

Having more nodules also improves bean plants’ ability to make volatile organic compounds when they first get attacked by the beetles, which drives them away.  Meanwhile, the more “infected” lima beans become with Rhizobium, the less extrafloral nectar they produce.  This makes them less attractive to ants, who otherwise farm aphids at the expense of bean plants.

Sources:

  • Ballhorn, James and al. Colonization by nitrogen‑fxing Frankia bacteria causes
    short‑term increases in herbivore susceptibility in red alder
    (Alnus rubra) seedlings. Oecologia. 2017 https://cbs.umn.edu/sites/cbs.umn.edu/files/public/downloads/Ballhornetal2017.pdf
  • Thamer, Sylvia and al. Dual benefit from a below-ground symbiosis: nitrogen fixing rhizobia promote growth and defense against a specialist herbivore in a cyanogenic plant. Plant and Soil.  April 2011.
  • James Mauseth. Botany, An Introduction to Plant Biology. Jones and Bartlett. 2008
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