29.12.11

Test Tube Science:Dancing Raisin


Materials:
   -One test tubes
   -One raisin
   -10 mL soda pop

Background:
For a gas to come out of a liquid it needs a nucleation site.  The raisin provides nucleation sites for the carbon dioxide in the soda pop.  The carbon dioxide sticks to the raisin surface until it is brought to the surface of the soda.  The bubbles pop and the raisin drops to the bottom and the process repeats.

Directions:
Pour 10 mL soda into the test tube.  Now place the raisin into the soda.  Watch what happens.  What else can you get to dance (try a pea or peanut, bead or button)?  Does the time between rising and falling change over time?

27.12.11

Happy Birthday Louis Pasteur

Louis Pasteur was born today, December 27, in 1822. Pasteur's early work as a chemist resolved a problem concerning the nature of tartaric acid. A solution of this compound derived from living things (specifically, wine lees) rotated the plane of polarization of light passing through it. The mystery was that tartaric acid derived by chemical synthesis had no such effect, even though its reactions were identical and its elemental composition was the same.

Upon examination of the minuscule crystals of synthetic sodium ammonium tartrate, Pasteur noticed that the crystals came in two asymmetric forms that were mirror images of one another. Tediously sorting the crystals by hand gave two forms of the compound: solutions of one form rotated polarized light clockwise, while the other form rotated light counterclockwise. An equal mix of the two had no polarizing effect on light. Pasteur correctly deduced that the molecule in question was asymmetric and could exist in two different forms that resemble one another as would left- and right-hand gloves, and that the organic form of the compound consisted purely of the one type. This was the first demonstration of chiral molecules.

22.12.11

Happy Birthday Vladimir Markovnikov

Vladimir Markovnikov, born December 22, 1838, was a Russian scientist who stated with the addition of water to an alkene to form an alcohol, the hydroxyl group bonds to the carbon that has the greater number of carbon-carbon bonds, while the hydrogen bonds to the carbon on the other end of the double bond, the one that has more carbon-hydrogen bonds.

23.11.11

Happy Birthday Johannes van der Waals

Johannes van der Waals, born November 23, 1837, is famous for his work on the equation of state for gases and liquids which describe the relation between the pressure, volume, and temperature of fluids (gases and liquids). He developed a model in which the liquid and the gas phase of a substance merge into each other in a continuous manner. It shows that the two phases are in fact of the same nature. In deriving his equation of state, van der Waals assumed not only the existence of molecules (which in physics was disputed at the time), but also that they are of finite size, and attract each other. Since he was one of the first to postulate an intermolecular force, however rudimentary, such a force is now sometimes called a van der Waals force.

7.11.11

Happy Birthday Maria Sklodowska Curie

Marie Curie, born  Maria Sklodowska on November 7, 1867. Through several years' unceasing work in the most difficult physical conditions, Maria and her French husband Pierre Curie, processed several tons of pitchblende, progressively concentrating the radioactive substances and eventually isolating the chloride salts (refining RaCl2 on April 20, 1902) and identifying two previously unknown chemical elements. The first, they named "polonium," in honor of Marie's native country, Poland, and the other "radium," for its intense "radioactivity" — a word coined by Marie.  In 1903 she completed her doctoral degree and became the first woman in France to do so.  In the same year, she received her first of two Nobel Prizes.  She is the only person to receive two Nobel Prizes in different fields of science.

23.10.11

Happy Mole Day

An unofficial holiday celebrated among chemists in North America on October 23, between 6:02 AM and 6:02 PM, making the date 6:02 10/23. The time and date are derived from the Avogadro constant, which is approximately 6.02×1023, defining the number of particles (atoms or molecules) in a mole.  The mole is one of the seven base SI units the other six are:

Measurable Name Abbreviation
mass kilogram kg
distance meter m
time second s
temperature kelvin K
electrical current ampere A
luminous intensity candela cd

21.10.11

Happy Birthday Alfred Nobel

Alfred Nobel, born October 21, 1833, is famous for inventing dynamite and using the fortune made from dynamite to fund the Nobel Prizes. The erroneous publication in 1888 of a premature obituary of Nobel by a French newspaper, condemning him for his invention of dynamite, is said to have brought about his decision to leave a better legacy after his death. The obituary stated "Le marchand de la mort est mort ("The merchant of death is dead") and went on to say, "Dr. Alfred Nobel, who became rich by finding ways to kill more people faster than ever before, died yesterday.”

8.10.11

Happy Birthday Henri Le Chatelier

Henri Le Chatelier, born October 8, 1850.  Le Chatelier is most famous for the law on chemical equilibrium which bears his name: If a chemical system at equilibrium experiences a change in concentration, temperature, or total pressure, the equilibrium will shift in order to minimize that change.

1.10.11

Less Newt

Organic synthesis is a lot like witchcraft...but with less newt.

6.9.11

Happy Birthday John Dalton

John Dalton, born September 6, 1766, was an English chemist known for his Atomic Theory which had the following five points:

  1. Elements are made of tiny particles called atoms.
  2. All atoms of a given element are identical.
  3. The atoms of a given element are different from those of any other element.
  4. Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers of types of atoms.
  5. Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process. A chemical reaction simply changes the way atoms are grouped together.  

Unfortunately, Dalton had an additional statement that prevented his theory from being accepted for many years: When atoms combine in only one ratio, "..it must be presumed to be a binary one, unless some cause appear to the contrary."

Dalton had no evidence to support this statement from his theory and it caused him to wrongly assume that the formula for water was OH and ammonia was NH. Because of this, Dalton's experimental data did not support most of the conclusions he drew from it.

Amazingly, all but two of the 200 year old statements in Dalton's Atomic Theory are still believed to be true by scientists today. The statement "Atoms cannot be subdivided, created, or destroyed into smaller particles when they are combined, separated, or rearranged in chemical reactions" is inconsistent with the existence of nuclear fusion and fission, although such processes are nuclear reactions, not chemical reactions. In addition, the statement "All atoms of a given element are identical in their physical and chemical properties" is not precisely true, as the different isotopes of an element have varying numbers of neutrons in their nuclei, though the number of protons remains consistent.

Dalton's method for representing the "elements or ultimate particles"

Figure name weight
  1. Hydrogen 1
  2. Azote 5
  3. Carbone or charcoal 5
  4. Oxygen 7
  5. Phosphorus 9
  6. Sulpher 13
  7. Magnesia 20
  8. Lime 23
  9. Soda 28
  10. Potash 42
  11. Strontites 46
  12. Barytes 68
  13. Iron 38
  14. Zinc 56
  15. Copper 56
  16. Lead 95
  17. Silver 100
  18. Platina 100
  19. Gold 140
  20. Mercury 167
  21. An atom of water or steam, composed of 1 of oxygen and 1 of hydrogen, retained in physical contact by a strong affinity, and supposed to be surrounded by a common atmosphere of heat; its relative weight = 8 
  22. An atom of ammonia, composed of 1 of azote and 1 of hydrogen -6
  23. An atom of nitrous gas composed of 1 of azote and 1 of oxygen - 12
  24. An atom of olefiant gas, composed of 1 of carbone and 1 of hydrogen-6 
  25. An atom of carbonic oxide composed of 1 of carbone and 1 of oxygen -12
  26. An atom of nitrous oxide, 2 azote + 1 oxygen - 17
  27. An atom of nitric acid. 1 azote + 2 oxygen -19
  28. An atom of carbonic acid, 1 carbone + 2 oxygen-19
  29. An atom of carburetted hydrogen, 1 carbone + 2 hydrogen-7
  30. An atom of oxynitric acid, 1 azote + 3 oxygen-26
  31. An atom of sulphuric acid, 1 sulphur + 3 oxygen-34
  32. An atom of sulphuretted hydrogen, 1 sulphur + 3 hydrogen - 15
  33. An atom of alcohol, 3 carhone + 1 hydrogen - 16
  34. An atom of nitrous acid, 1 nitric acid + 1 nitrous gas - 31
  35. An atom of acetous acid, 2 carbone + 2 water - 26
  36. An atom of nitrate of ammonia, 1 nitric acid + 1ammonia + 1 water-33
  37. An atom of sugar, 1 alcohol + 1 carbonic arid - 35

26.8.11

Happy Birthday Antoine Lavoisier

Antoine Lavoisier, born August 26, 1743, French chemist and one of the fathers of modern chemistry.  He brought chemical experimentation from the philosophical alchemists to the scientific chemists.  He stated the first version of the law of conservation of mass, co-discovered, recognized, and named oxygen (1778), as well as hydrogen, disproved the phlogiston theory, introduced the metric system, wrote the first extensive list of elements, and helped to reform chemical nomenclature all before being beheaded on 8 May 1794 in Paris, at the age of 50.

9.8.11

Happy Birthday Amedeo Avogadro

Amedeo Avogadro, born August 9, 1776, was an Italian chemist known for his work on the theory of molarity and molecular weight.  While he didn’t discover the number of particles in one mole of a substance, 6.022×1023, is now know as Avogadro’s number.

(edit:spelling)

1.8.11

I have Mass. You have Mass...

Man: I have mass.  You have mass.  We are naturally attracted.
Woman: It's a purely physical attraction.

25.7.11

Happy Birthday Rosalind Elsie Franklin

Rosalind Elsie Franklin, born July 25, 1920, was a Physical chemist and crystallographer who worked on the X-ray diffraction images of DNA which formed a basis of Watson and Crick's hypothesis of the double helical structure of DNA in their 1953 publication.  When published in its own article along side Watson and Crick’s, her data constituted critical evidence of their hypothesis.  Later, she led pioneering work on the tobacco mosaic and polio viruses.

22.7.11

Test Tube Science: Black Bean Indicator

There are lots of acid/base indicators available in the home.  The one I'm going to talk about today is an indicator made from black beans.

Marcelle was making a big batch of feijoada and started the black beans soaking the night before we were going to have it for dinner.  As she was preparing to pour off the blue/purple water they had soaked in I asked her to save some for me.

The dinner was delicious. And I decided that I'd see what colors I could come up with after dinner.  In the picture below you can see the spectrum of colors obtained from my black bean juice with vinegar and baking soda.

Black bean indicator: acidic on the left, neutral in the middle and basic on the right.
To make your own indicator take 10-15 dry black beans put them in a test tube and cover them with water.  Let them soak for 10-12 hours for the most concentrated solution.  Now you can remove the water and use it as an indicator in other solutions.  Dilute the black bean juice 1 part juice to 4 parts test solution.

If you want to get some indicator in 10 minutes instead of 10 hours you can soak the beans in 70% isopropyl alcohol.  The alcohol will make a solution much faster.

Acid, neutral, and basic forms of anthocyanins.
The primary color changing molecules in black beans are anthocyanins. As the pH of the solution changes the structure of the molecule changes.  This changes its absorption spectrum thus changing the color of the solution. These reactions are in equilibrium making them great natural indicators.

1.7.11

U and I Together

Man: If I were designing the periodic table I'd put U and I together.
Woman: A then both Mendeleev and I would cry.

28.6.11

Happy Birthday Emil Erlenmeyer

Emil Erlenmeyer, born June 28, 1825, is the inventor of the conical flask which bears his name.

12.5.11

Happy Birthday Dorthy Mary Crowfoot Hodgkin

Dorothy Mary Crowfoot Hodgkin, born 12 May 1910, was a British founder of protein crystallography. She pioneered the technique of X-ray crystallography, a method used to determine the three dimensional structures of molecules. Among her most influential discoveries are the determination of the structure of penicillin, insulin, and vitamin B12 for which she was awarded the Nobel Prize in Chemistry. In 1969, after 35 years of work, Hodgkin was able to decipher the structure of insulin. She is regarded as one of the foremost scientists in the field of X-ray crystallography of natural molecules.

25.4.11

Test Tube Science: Fizzle Fizzle

Awhile ago I sent out some test tubes and pipettes to my nieces and nephews.  I said that I would be posting some experiments that you could do with them.  Here is the first experiment.

This is a fun way to start using your test tubes and pipets.  To run this experiment place about 1mL of sodium bicarbonate (baking soda) in the bottom of a test tube. Now fill your pipette with 5% acetic acid (white vinegar) and squirt it into the test tube. Be prepared for this to overflow the test tube, it is part of the fun. Repeat the addition of acid until no more bubbling occurs. The first time I did this with my son he was about 22 months old.  I asked him to put the tube by his face and asked if he could feel the fizzing.  He then took to calling it fizzle fizzle and often asked for it by name.

Try this again but instead of adding all of the baking soda at once place half of the soda in and then place a drop of food coloring in the test tube taking care to have it drop in the center of the baking soda.  Then add the rest of the baking soda.  After the second or third addition of vinegar the foam will turn the color of the dye much to the delight of the young scientist.  

This activity is not just for the youngest scientists.  Because carbon dioxide is more dense than air the test tube will stay filled with carbon dioxide.  This can then be poured over a match extinguishing the flame.  This shows  both the greater density of carbon dioxide and the need of oxygen during combustion.

Another variation on the sodium bicarbonate acetic acid theme is to make rockets out of film canisters.  Place some baking soda in the film canister next add some vinegar and quickly snap on the lid.  Invert the canister so that the lid is on the table and wait.  In a short time the canister will pop a few feet into the air.  I've done this a few time with cub scouts and they love the excitement of not knowing when the rocket will launch.

The last suggestion for baking soda and vinegar is a lab fire extinguisher.  Some old fire extinguishers had an aqueous solution of baking soda  and a small bottle of sulfuric acid in them.  When the fire extinguisher was inverted the acid would react with the baking soda and produce carbon dioxide.  The carbon dioxide would then force the water out and it could be used to extinguish the fire.  You can build your own lab fire extinguisher as shown in this illustration from the Golden Book of Chemistry.


24.2.11

Writing With Amino Acids

Most of the letters in the alphabet have been used in the standard abbreviations for the 20 proteinogenic amino acids.  If you add in a few other amino acids and some uncertainties all of the letters are accounted for.  This means you can code words into peptides.  I'll show a few examples below:

STAY
 Each amino acid starts with the nitrogen so in this image you can see there are four amino acids (serine, threonine, alanine, and tyrosine) one for each letter in "Stay."

COSBY
Notice the R in the diagram (just above the last NH) comes from "B" which indicates either asparagine or aspartic acid.  The R indicates where asparagine and aspartic acid are different.

AHLSTROM
SUMMERSTAY
Can you identify the already seen "Stay" portion?
HOMER
So now you can pass notes during chemistry class.


4.1.11

British Vs American Elements

I wrote earlier about the elements using Google's ngram service and here I present some comparisons of british vs American spellings of a couple of elements.

Aluminium vs Aluminum


Caesium vs Cesium

As you can see the British spelling is higher to begin with but then falls to the American spelling.